JPH06195871A - Prevention device for inversion phenomenon - Google Patents

Abstract

PURPOSE:To obtain a prevention device for inversion phenomenon of small circuit scale by detecting a part in which a zero cross point is omitted from an input digital FM signal and an output signal of a side band wave suppression filter by an inversion phenomenon detector. CONSTITUTION:An inversion phenomenon detector 4 detects the maximum point and the minimum point of an output signal of a side band wave suppression filter 3. Also, the detector discriminates whether a code of an input digital FM signal coincides with a code of the output signal of the filter 3 or not, when an AC zero level is made the reference. A selector 5 selects either of an output x(k-1) of a delay compensator 2 or an output xf(k-1) of the filter 3 and outputs it to an output terminal 6. Thus, by constituting the detector 4 with the detector which detects the maximum point and the minimum point of the output signal of the filter 3 and the discriminator which discriminates whether the code of the digital FM signal coincides with the code of the output signal of the filter 3 or not, a prevention device for inversion phenomenon of which a circuit scale is small and which is easy to realized can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inversion phenomenon prevention device for preventing an inversion phenomenon in an FM signal.

[0002]

2. Description of the Related Art As a conventional inversion phenomenon prevention device, a device generally called a double limiter is known.
For example, FIG. 22 is a block circuit diagram of a double limiter which is a conventional inversion phenomenon preventing device disclosed in Japanese Patent Laid-Open No. 62-219372. In the figure, 601 is an input terminal of a reproduced FM signal, 602 is a high-pass filter (hereinafter, referred to as “HPF”) that passes a carrier component of the input FM signal and largely attenuates a lower sideband component, and 603 is an amplitude of the input signal. A limiter for eliminating a difference and obtaining a sinusoidal output signal having a constant amplitude, 604 is a phase corrector for correcting the phase, and 60
5 is a low-pass filter (hereinafter referred to as "LPF") that sufficiently attenuates the carrier component of the input FM signal, 606 is a combiner that combines the outputs of the phase corrector 604 and LPF 605, and 607 is an AM demodulator that follows. A limiter 608 that keeps the amplitude constant so that the demodulation output is not distorted by the component, and 608 is an FM signal output terminal.

In the conventional device for preventing inversion phenomenon configured as described above, the carrier component is limited by the limiter 60 in the portion where the carrier component of the input FM signal is small and the inversion phenomenon is likely to occur.
It is amplified until it becomes a predetermined amplitude by 3 (however, S / N
Therefore, the FM signal in which only the carrier component is amplified and the inversion phenomenon is unlikely to occur is obtained at the output of the combiner 606. In the portion where the carrier component of the input FM signal is large and the inversion phenomenon does not occur, the carrier component is almost not amplified by the limiter 603 (thus S / N is not deteriorated) and has a predetermined amplitude. Input F
An FM signal approximately equal to the M signal is obtained. Therefore, the FM signal that does not always cause the inversion phenomenon is output.

In order to deal with a quantized digital FM signal, an example in which the inversion phenomenon prevention circuit is directly realized by a digital signal processing circuit is also disclosed in Japanese Patent Laid-Open No. 62-2.
FIG. 23 is a block circuit diagram thereof, which is disclosed in Japanese Patent No. 19372.

This device inputs / outputs a digital FM signal which is a quantized FM signal. In FIG. 23, 701 is an input terminal for a digital FM signal, 702 is an HPF, 703 is a limiter that makes the output amplitude of the HPF 702 a constant value, 704 is an amplitude detector that obtains an amplitude signal that is the amplitude of the output signal of the HPF 702, and 705. Is HPF70
It is a divider that divides the output signal of 2 by the amplitude signal from the amplitude detector 704 to obtain a carrier component of constant amplitude. 706
Is an LPF, 707 is a combiner for combining the output of the limiter 703, that is, the output of the divider 705 and the output of the LPF 706, and 708 is an output terminal of the digital FM signal. H
Since the PF 702 and LPF 706 can easily have a linear phase characteristic, a phase corrector is unnecessary, and the limiter 60 shown in FIG.
Reference numeral 7 is omitted because it is a circuit that is not directly related to the prevention of the inversion phenomenon.

The basic operation of the conventional digital inversion phenomenon prevention device configured as described above is the same as that of the case of FIG.

[0007]

However, the second conventional example requires the amplitude detector 704. In order to configure the amplitude detector 704, when an input to the amplitude detector 704 is X, a 90-degree phase shifter that shifts X by 90 degrees and a 90-degree phase-shifted signal are Y, (X2 + Y2)
An arithmetic unit for calculating the square root of is required, and the circuit scale is considerably large.

Further, a divider 705 having a circuit scale larger than that of the multiplier is required. Moreover, while the output signal of the LPF 706 is a sideband component with a small amplitude,
Since the output signal of 702 is a carrier component having a large amplitude, it is necessary to increase the data word length. Therefore, there is a problem that the circuit scale of the divider 705 and the amplitude detector 704 becomes larger, which makes it difficult to realize the digital inversion phenomenon prevention device.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an inversion phenomenon prevention device having a small circuit scale, a low cost, and an easy realization.

[0010]

According to a first aspect of the present invention, there is provided an inversion phenomenon preventing device which receives a quantized digital FM signal as an input,
A sideband suppression filter that suppresses the upper and lower sidebands or the lower sideband, a detector that detects the maximum and minimum points of the output signal of the sideband suppression filter, and the digital FM signal when the AC zero level is used as a reference. And a discriminator for discriminating whether or not the signs of the output signals of the sideband suppression filters match, an inversion phenomenon detector constituted by the detector and the discriminator, and an output result of the inversion phenomenon detector. A selector for selecting either the digital FM signal or the output signal of the sideband suppression filter is provided.

According to a second aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppression filter for suppressing upper and lower sidebands or a lower sideband, and the digital FM signal has a preset range. A detector for detecting the internal frequency, a detector for detecting a maximum point and a minimum point of the output signal of the sideband suppression filter, the digital FM signal and the sideband suppression filter when an AC zero level is used as a reference. Discriminator for discriminating whether or not the signs of the output signals of the two discriminate, an inversion phenomenon detector composed of the two detectors and the discriminator, and the digital signal according to the output result of the inversion phenomenon detector. It is provided with a selector for selecting either the FM signal or the output signal of the sideband suppression filter.

According to another aspect of the present invention, there is provided a device for preventing inversion phenomenon, which receives a quantized digital FM signal as an input and suppresses upper and lower sidebands or lower sidebands, and an output signal of the sideband suppression filter. A detector for detecting a maximum point and a minimum point, a subtraction result of the output signal of the sideband suppression filter and a signal preceding it in time, and a multiplication result of the subtraction result and the digital FM signal are determined. A discriminator, the detector, and an inversion phenomenon detector including the discriminator, and a selection for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the inversion phenomenon detector. It is equipped with a vessel.

According to a fourth aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppression filter for suppressing upper and lower sidebands or a lower sideband, and the digital FM signal has a preset range. Detector for detecting that the output signal of the sideband suppression filter, the detector for detecting the maximum point and the minimum point of the output signal of the sideband suppression filter, and the output signal of the sideband suppression filter and the signal preceding it in time. Of the subtraction result, the discriminator for discriminating the multiplication result of the subtraction result and the digital FM signal, the inversion phenomenon detector composed of the two detectors and the discriminator, and the output result of the inversion phenomenon detector. A selector for selecting either the digital FM signal or the output signal of the sideband suppression filter is provided.

According to a fifth aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppressing filter for suppressing upper and lower sidebands or a lower sideband, and the digital FM signal has a preset range. Of the output signals of the digital FM signal and the output signal of the sideband suppression filter when an AC zero level is used as a reference. A discriminator for discriminating whether or not the codes match, an inversion phenomenon detector constituted by the two detectors and the discriminator, and the digital FM signal and the side band according to the output result of the inversion phenomenon detector. And a selector for selecting one of the output signals of the wave suppression filter.

According to another aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppression filter for suppressing upper and lower sidebands or a lower sideband, and a maximum point and a minimum point of the digital FM signal. A detector for detecting a point; a subtraction result for the subtraction result of the output signal of the sideband suppression filter and a signal preceding it in time; and a discrimination device for determining a multiplication result of the subtraction result and the digital FM signal. An inversion phenomenon detector composed of a detector and a discriminator,
A selector for selecting either the digital FM signal or the output signal of the sideband suppression filter according to the output result of the inversion phenomenon detector is provided.

According to a seventh aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppressing filter for suppressing upper and lower sidebands or a lower sideband, and the digital FM signal has a preset range. And a detector for detecting the maximum and minimum points of the digital FM signal, and a result of subtraction between the output signal of the sideband suppression filter and the signal preceding it in time. ,
A discriminator that discriminates a multiplication result of the subtraction result and the digital FM signal, an inversion phenomenon detector including the two detectors and the discriminator, and the digital FM according to an output result of the inversion phenomenon detector. A selector for selecting either the signal or the output signal of the sideband suppression filter is provided.

According to another aspect of the invention, there is provided a device for preventing inversion phenomenon, which receives a quantized digital FM signal as an input and suppresses upper and lower sidebands or lower sidebands, and an output signal of the sideband suppression filter. A detector for detecting a maximum point and a minimum point, a subtraction result of the output signal of the sideband suppression filter and a signal later in time, and a multiplication result of the subtraction result and the digital FM signal are determined. A discriminator, the detector, and an inversion phenomenon detector including the discriminator, and a selection for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the inversion phenomenon detector. It is equipped with a vessel.

According to a ninth aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppression filter for suppressing upper and lower sidebands or a lower sideband, and the digital FM signal has a preset range. A detector that detects that the output signal of the sideband suppression filter, the detector that detects the maximum point and the minimum point of the output signal of the sideband suppression filter, the output signal of the sideband suppression filter and a signal that is later in time than that. Of the subtraction result, the discriminator for discriminating the multiplication result of the subtraction result and the digital FM signal, the inversion phenomenon detector composed of the two detectors and the discriminator, and the output result of the inversion phenomenon detector. A selector for selecting either the digital FM signal or the output signal of the sideband suppression filter is provided.

According to a tenth aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppression filter for suppressing upper and lower sidebands or a lower sideband, and a maximum point and a minimum point of the digital FM signal. A detector for detecting a point; a subtraction result for the output signal of the sideband suppression filter and a signal that is later in time; and a discriminator for determining the multiplication result of the subtraction result and the digital FM signal. An inversion phenomenon detector composed of a detector and a discriminator, and a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the inversion phenomenon detector are provided. It is a thing.

According to another aspect of the invention, there is provided a device for preventing inversion phenomenon, which receives a quantized digital FM signal as an input and which suppresses upper and lower sidebands or lower sidebands, and a range in which the digital FM signal is preset. And a detector for detecting the maximum and minimum points of the digital FM signal, and a subtraction result of the output signal of the sideband suppression filter and a signal that is later in time. A discriminator for discriminating a multiplication result of the subtraction result and the digital FM signal, an inversion phenomenon detector formed by the two detectors and the discriminator, and the digital signal according to an output result of the inversion phenomenon detector. It is provided with a selector for selecting either the FM signal or the output signal of the sideband suppression filter.

A device for preventing inversion phenomenon according to a twelfth aspect of the present invention receives a quantized digital FM signal as an input, and a sideband suppression filter for suppressing upper and lower sidebands or lower sidebands, the digital FM signal, and the digital FM. A discriminator for discriminating between a subtraction result of the signal and a signal temporally preceding the digital FM signal and a subtraction result of the digital FM signal and a signal temporally subsequent to the digital FM signal, and the discriminator. And the digital F in accordance with the output result of the inversion phenomenon detector.
It is provided with a selector for selecting either the M signal or the output signal of the sideband suppression filter.

According to a thirteenth aspect of the present invention, a device for preventing inversion phenomenon receives a quantized digital FM signal as an input, a sideband suppressing filter for suppressing upper and lower sidebands or a lower sideband, and the digital FM signal has a preset range. A detector for detecting that it is within the range, the digital FM signal, the subtraction result of the digital FM signal and a signal temporally preceding the digital FM signal, the digital FM signal and the digital FM signal Discriminator for discriminating the subtraction result from the subsequent signal, the inversion phenomenon detector constituted by the detector, and the inversion phenomenon detector, and the digital FM signal and the side band according to the output result of the inversion phenomenon detector. And a selector for selecting one of the output signals of the wave suppression filter.

[0023]

According to the invention of claim 1, a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter;
The input digital FM signal and the sideband suppression according to the output result of the discriminator that determines whether the sign of the input digital FM signal and the output signal of the sideband suppression filter match when the AC zero level is used as a reference. By selecting and outputting any one of the output signals of the filter, the input digital FM is directly applied to the FM signal in which the upper sideband and the lower sideband are unbalanced and the amplitude of the carrier component is large and the inversion phenomenon does not occur. The signal is output, but in the part where the carrier component is small in the detector and the discriminator and it is judged that the inversion phenomenon occurs, the signal is passed through the carrier suppression filter corresponding to the relatively large carrier component. A digital FM signal that does not cause the inversion phenomenon and suppresses S / N deterioration as much as possible can be obtained with a device that is inexpensive and has a small circuit scale. It is possible.

According to the invention of claim 2, a detector for detecting that the input digital FM signal is within a preset range, and a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter. And the input digital FM signal and the side band depending on the output result of the discriminator that determines whether the sign of the digital FM signal and the output signal of the side band suppression filter match when the AC zero level is used as a reference. By selecting and outputting one of the output signals of the wave suppression filter, an FM signal in which the upper sideband and the lower sideband are unbalanced is directly input to a portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although the digital FM signal is output, the carrier component is relatively increased in the portion where the detector and the discriminator determine that the carrier component is small and causes the inversion phenomenon. By outputting a signal that has passed through a carrier suppression filter corresponding to the above, a digital FM signal that does not cause an inversion phenomenon and that suppresses S / N deterioration as much as possible can be obtained with a device that is inexpensive and has a small circuit scale. You can

According to the third aspect of the present invention, a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter, the output signal of the sideband suppression filter, and the signal preceding it in time. Of the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the subtraction result and the output result of the discriminator that determines the multiplication result of the subtraction result and the digital FM signal. As a result, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur with respect to the FM signal in which the upper sideband and the lower sideband are unbalanced.
In the part where it is determined that the carrier component is small in the detector and the discriminator to cause the inversion phenomenon, the inversion phenomenon does not occur by outputting the signal passed through the carrier suppression filter corresponding to the relatively large carrier component. , And S /
It is possible to obtain a digital FM signal in which N deterioration is suppressed as much as possible with a device that is inexpensive and has a small circuit scale.

According to the invention of claim 4, a detector for detecting that the input digital FM signal is within a preset range and a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter. And the subtraction result of the output signal of the sideband suppression filter and the signal that is earlier in time than it,
According to the output result of the discriminator that discriminates the multiplication result of the subtraction result and the digital FM signal, the input digital F
By selecting and outputting either the M signal or the output signal of the sideband suppression filter, the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the upper sideband and the lower sideband are unbalanced. In the portion, the input digital FM signal is output as it is, but in the portion where it is determined that the carrier component is small in the detector and the discriminator and the inversion phenomenon occurs, it is passed through the carrier suppression filter corresponding to the relatively large carrier component. By outputting the signal, it is possible to obtain a digital FM signal in which the inversion phenomenon does not occur and the S / N deterioration is suppressed as much as possible with a low cost and a small circuit scale.

According to the invention of claim 5, a detector for detecting that the input digital FM signal is within a preset range, a detector for detecting a maximum point and a minimum point of the digital FM signal, and an alternating current Depending on the output result of the discriminator that determines whether or not the sign of the digital FM signal and the output signal of the sideband suppression filter match when the zero level is used as a reference, By selecting and outputting one of the output signals, the input digital FM signal is directly input to the FM signal in which the upper sideband and the lower sideband are unbalanced, in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although it is output, in the part where the carrier component is small in the detector and the discriminator and it is judged that the inversion phenomenon occurs, it is possible to increase the carrier component relatively. By outputting a signal through a carrier suppression filter, without causing inversion, moreover it is possible to obtain an inexpensive circuit scale small device in cost digital FM signal while minimizing the S / N deterioration.

According to the sixth aspect of the present invention, the detector for detecting the maximum and minimum points of the input digital FM signal, the subtraction result of the output signal of the sideband suppression filter and the signal preceding it in time. , The subtraction result and the digital FM
By selecting and outputting either the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the discriminator that determines the multiplication result with the signal, the upper sideband and the lower sideband are separated. With respect to a balanced FM signal, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur, but the portion where the carrier component is small in the detector and the discriminator is determined to cause the inversion phenomenon. Then, by outputting a signal that has passed through a carrier wave suppression filter corresponding to a relatively large carrier wave component, a digital FM signal that does not cause an inversion phenomenon and suppresses S / N deterioration as much as possible is inexpensive. Can be obtained with a device having a small circuit scale.

According to the invention of claim 7, a detector for detecting that the input digital FM signal is within a preset range, a detector for detecting a maximum point and a minimum point of the digital FM signal, and a side band. According to the subtraction result of the output signal of the wave suppression filter and the signal preceding in time, and the output result of the discriminator that discriminates the multiplication result of the subtraction result and the digital FM signal, the input digital FM signal is output. By selecting and outputting one of the output signals of the sideband suppression filter, the FM signal in which the upper sideband and the lower sideband are unbalanced is used as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although the input digital FM signal is output, the carrier component is relatively increased in the portion where the detector and the discriminator determine that the carrier component is small and causes the inversion phenomenon. By outputting a signal that has passed through a carrier suppression filter corresponding to the above, a digital FM signal that does not cause an inversion phenomenon and that suppresses S / N deterioration as much as possible can be obtained with a device that is inexpensive and has a small circuit scale. You can

According to the invention of claim 8, a detector for detecting a maximum point and a minimum point of the output signal of the sideband suppression filter, the output signal of the sideband suppression filter, and a signal timewise later than that. Of the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the subtraction result and the output result of the discriminator that determines the multiplication result of the subtraction result and the input digital FM signal. As a result, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur with respect to the FM signal in which the upper sideband and the lower sideband are unbalanced.
In the part where it is determined that the carrier component is small in the detector and the discriminator to cause the inversion phenomenon, the inversion phenomenon does not occur by outputting the signal passed through the carrier suppression filter corresponding to the relatively large carrier component. , And S /
It is possible to obtain a digital FM signal in which N deterioration is suppressed as much as possible with a device that is inexpensive and has a small circuit scale.

According to the invention of claim 9, a detector for detecting that the input digital FM signal is within a preset range and a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter. And a subtraction result between the output signal of the sideband suppression filter and a signal that is later in time than that,
According to the output result of the discriminator that discriminates the multiplication result of the subtraction result and the digital FM signal, the input digital F
By selecting and outputting either the M signal or the output signal of the sideband suppression filter, the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the upper sideband and the lower sideband are unbalanced. In the portion, the input digital FM signal is output as it is, but in the portion where it is determined that the carrier component is small in the detector and the discriminator and the inversion phenomenon occurs, it is passed through the carrier suppression filter corresponding to the relatively large carrier component. By outputting the signal, it is possible to obtain a digital FM signal in which the inversion phenomenon does not occur and the S / N deterioration is suppressed as much as possible with a low cost and a small circuit scale.

According to the tenth aspect of the invention, a detector for detecting the maximum and minimum points of the input digital FM signal,
The subtraction result of the output signal of the sideband suppression filter and the signal that is later in time, the subtraction result, and the digital F
By selecting and outputting either the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the discriminator that determines the multiplication result with the M signal, the upper sideband and the lower sideband are separated. With respect to an unbalanced FM signal, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur, but it is determined that the carrier component is small and the inversion phenomenon occurs in the detector and the discriminator. In the portion, a signal passed through a carrier suppression filter corresponding to a relatively large carrier component is output, so that the inversion phenomenon does not occur, and the digital FM signal in which the S / N deterioration is suppressed as much as possible is also cost effective. It can be obtained with a device that is inexpensive and has a small circuit scale.

According to the invention of claim 11, a detector for detecting that the input digital FM signal is within a preset range, a detector for detecting a maximum point and a minimum point of the digital FM signal, and a side band. An input digital FM signal is output according to the result of subtraction between the output signal of the wave suppression filter and a signal that is later in time, and the output result of a discriminator that determines the result of multiplication of the subtraction result and the digital FM signal. By selecting and outputting one of the output signals of the sideband suppression filter, the FM signal in which the upper sideband and the lower sideband are unbalanced is used as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although the input digital FM signal is output, the carrier component is relatively large in the portion where the detector and the discriminator determine that the carrier component is small and causes the inversion phenomenon. By outputting a signal that has passed through a carrier suppression filter corresponding to the above, a digital FM signal that does not cause an inversion phenomenon and suppresses S / N deterioration as much as possible can be obtained by a device with a low cost and a small circuit scale. be able to.

According to the twelfth aspect of the present invention, the subtraction result of the input digital FM signal, the digital FM signal and the signal temporally preceding the digital FM signal, the digital FM signal and the digital FM signal are used. By selecting and outputting either the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the discriminator that determines the subtraction result from the signal that is later in time, the upper sideband wave The input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the lower sideband is unbalanced.
In the part where it is determined that the carrier component is small in the detector and the discriminator to cause the inversion phenomenon, the inversion phenomenon does not occur by outputting the signal passed through the carrier suppression filter corresponding to the relatively large carrier component. , And S /
It is possible to obtain a digital FM signal in which N deterioration is suppressed as much as possible with a device that is inexpensive and has a small circuit scale.

According to the invention of claim 13, a detector for detecting that the input digital FM signal is within a preset range, the digital FM signal, the digital FM signal and the digital FM signal In accordance with the output result of the discriminator for discriminating the subtraction result of the previous signal and the subtraction result of the digital FM signal and the signal subsequent in time from the digital FM signal, the input digital F
By selecting and outputting either the M signal or the output signal of the sideband suppression filter, the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the upper sideband and the lower sideband are unbalanced. In the portion, the input digital FM signal is output as it is, but in the portion where it is determined that the carrier component is small in the detector and the discriminator and the inversion phenomenon occurs, it is passed through the carrier suppression filter corresponding to the relatively large carrier component. By outputting the signal, it is possible to obtain a digital FM signal in which the inversion phenomenon does not occur and the S / N deterioration is suppressed as much as possible with a low cost and a small circuit scale.

[0036]

【Example】

Example 1. A first embodiment according to the invention of claim 1 will be described with reference to FIG. Reference numeral 1 is an input terminal for a digital FM signal, 3 is a sideband suppression filter for suppressing upper and lower sidebands or lower sidebands of the digital FM signal, and 2 is digital as much as a delay time of a signal output by the sideband suppression filter 3. This is a delay compensator that delays a signal, and the outputs of the delay compensator 2 and the sideband suppression filter 3 are quantized signals at the same time. 4 is a delay compensator 2 and a sideband suppression filter 3
When the output of the reversal phenomenon detector 4 is 1, it is A
When the side is 0, the side B is selected and is output to the output terminal 6 of the digital FM signal.

Next, the operation of FIG. 1 will be described. Normally, the selector 5 selects B in advance. That is, the input terminal 1
The signal input to is output to the output terminal 6 as it is after being delayed by the delay corrector 2. However, the selector 5 selects the A side only when it is determined from the outputs of the delay corrector 2 and the sideband suppression filter 3 that the inversion phenomenon detector 4 demodulates as it is, and the inversion phenomenon occurs. The signal passed through the suppression filter 3 is output to the output terminal 6.

That is, F shown by the solid line in FIG.
If a quantized version of the M signal is input to the input terminal 1, the crossing point between the FM signal and the AC zero level disappears in the vicinity of x (n). Occurs. The output of the sideband suppression filter 3 at this time is the waveform shown by the broken line in FIG. 16, and x
In the vicinity of xf (n) corresponding to (n), the intersection with the zero level is restored, and the waveform does not cause the inversion phenomenon even when demodulated. However, since the lower sideband with good S / N is suppressed, the inversion phenomenon does not occur when demodulated, but S /
The demodulation output will be a bad N.

Therefore, normally, the waveform of the solid line in FIG. 16 is output for demodulation, but the inversion phenomenon detector 4 detects that the intersection with the zero level disappears near x (n). Then, only that portion is switched to the waveform of the broken line near xf (n) and output. That is, the FM shown in FIG.
If you output a signal (a diagram in which quantized signals are smoothly connected by a solid line) and demodulate, S / N will be extremely high.
It is possible to obtain a demodulation waveform that does not cause the inversion phenomenon because the intersection with the zero level is restored without deteriorating the noise.

FIG. 2 is a block circuit diagram of the inversion phenomenon detector 4 of the first embodiment. In FIG. 2, reference numerals 10, 11, and 12 denote delay units for delaying input data by one sample clock, and 1
Subtractors 3 and 14 output only the sign of the result of the subtraction, and output 1 only when the sign is negative and 0 otherwise.
15 and 16 are encoders that output only the sign of the input signal,
1 is output only when the value is negative, and 0 otherwise. 17,
18 is an XOR gate and 19 is an AND gate.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {xf
The code of (k) -xf (k-1)} and {xf (k + 1)-
When the signs of xf (k)} do not match, 1 is output, and when they match, 0 is output. That is, in xf (k) as shown in FIGS. 18 (a) and 18 (b), 1 is output when only a waveform that takes a maximum and a minimum is detected.

The output of the XOR gate 17 is x (k).
1 when the sign of and the sign of xf (k) do not match,
If they match, 0 is output. That is, the output of the AND gate 19 outputs 1 when the waveform is as shown in FIGS. 19A and 19B, and 0 otherwise.

The inversion phenomenon can be detected by the above operation, and the waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a) and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 2. Embodiment 2 according to the invention of claim 2
Will be explained. The configuration of the entire inversion phenomenon prevention circuit is as shown in FIG. 1, and the operation thereof is also the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 3 is a block circuit diagram of the inversion phenomenon detector 4 of the second embodiment. In the figure, 1
0, 11, 12 are delay devices for delaying the input data by one sample clock, and 13, 14, 22 are subtractors for outputting only the sign of the result of the subtraction, which is 1 only when it is negative and otherwise. Outputs 0. Reference numerals 15 and 16 are encoders that output only the sign of the input signal, and output 1 only when the sign is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 20 is an AND gate that outputs 1 only when all three inputs are 1, and outputs 0 otherwise. Reference numeral 21 is an absolute value calculator for calculating the absolute value of the input signal, and 23 is a memory for holding a preset value D.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {xf
The code of (k) -xf (k-1)} and {xf (k + 1)-
When the signs of xf (k)} do not match, 1 is output, and when they match, 0 is output. The output of the subtractor 22 is
When | x (k) | <D, 1 is output, and otherwise 0 is output. The output of the XOR gate 17 outputs 1 when the code of x (k) and the code of xf (k) do not match, and outputs 0 when they match. That is, the output of the AND gate 20 becomes 1 at the time k satisfying | x (k) | <D.
, X as shown in FIGS. 18 (a) and 18 (b).
In f (k), only the waveform that takes the maximum and the minimum is detected, and the output of the XOR gate 17 becomes 1. Therefore, as shown in FIGS. 19A and 19B, AND when the waveform is 1, otherwise 0
The gate 20 outputs.

With the above operation, the reversal phenomenon can be detected. In the case of FIG. 19A, the waveform of FIG.
In the case of FIG. 19B, the inversion phenomenon can be prevented by outputting the waveform of FIG. 20B to the output terminal 6 of FIG.

Example 3. Embodiment 3 according to the invention of claim 3
Will be explained. The overall configuration of the inversion phenomenon prevention circuit is as shown in FIG. 1 and the operation thereof is the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 4 is a block circuit diagram of the inversion phenomenon detector 4 of the third embodiment. In the figure, 1
0, 11, 12 are delay units for delaying the input data by one sample clock, 13 and 14 are subtracters for outputting only the sign of the result of subtraction, 1 is set only when the value is negative, and 0 otherwise. Output. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 19 is an AND gate.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {xf
The code of (k) -xf (k-1)} and {xf (k + 1)-
When the signs of xf (k)} do not match, 1 is output, and when they match, 0 is output. That is, in xf (k) as shown in FIGS. 18 (a) and 18 (b), 1 is output when only a waveform that takes a maximum and a minimum is detected. The output of the XOR gate 17 outputs 1 when the sign of x (k) and the sign of {xf (k) -xf (k-1)} do not match, and outputs 0 when they match. . That is, the output of the AND gate 19 is 1 when the waveform is as shown in FIGS. 19A and 19B, and 0 otherwise.
Is output.

The inversion phenomenon can be detected by the above operation, and the waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a) and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 4. Embodiment 4 according to the invention of claim 4
Will be explained. The overall configuration of the inversion phenomenon prevention circuit is as shown in FIG. 1 and the operation thereof is the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 5 is a block circuit diagram of the inversion phenomenon detector 4 of the fourth embodiment. In the figure, 1
0, 11, 12 are delay devices for delaying the input data by one sample clock, and 13, 14, 22 are subtractors for outputting only the sign of the result of the subtraction, which is 1 only when it is negative and otherwise. Outputs 0. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 20 is an AND gate that outputs 1 only when all three inputs are 1, and outputs 0 otherwise. Reference numeral 21 is an absolute value calculator for calculating the absolute value of the input signal, and 23 is a memory for holding a preset value D.

The output of the delay corrector 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {xf
The code of (k) -xf (k-1)} and {xf (k + 1)-
When the signs of xf (k)} do not match, 1 is output, and when they match, 0 is output. The output of the subtractor 22 is
When | x (k) | <D, 1 is output, and otherwise 0 is output. Further, the output of the XOR gate 17 outputs 1 when the code of x (k) and the code of {xf (k) -xf (k-1)} do not match, and outputs 0 when they match. That is,
The output of the AND gate 20 becomes 1 because | x (k) |
At time k satisfying <D, only the waveform that takes the maximum and the minimum is detected in xf (k) as shown in FIGS. 18A and 18B, and the output of the XOR gate 17 is 1 It is time to
The AND gate 20 outputs 1 when the waveform is as shown in (a) and (b) of 9 and 0 otherwise.

The inversion phenomenon can be detected by the above operation. In the case of FIG. 19 (a), the waveform of FIG. 20 (a) is shown, and in the case of FIG. 19 (b), the waveform of FIG. 20 (b) is shown. By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 5. Embodiment 5 according to the invention of claim 5
Will be explained. The overall configuration of the inversion phenomenon prevention circuit is as shown in FIG. 1 and the operation thereof is the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 6 is a block circuit diagram of the reversal phenomenon detector of the fifth embodiment. In the figure, 10,
Reference numerals 11 and 12 denote delay devices for delaying the input data by one sample clock, and 13, 14 and 22 are subtractors for outputting only the sign of the result of the subtraction, which outputs 1 only when the value is negative, and 0 otherwise. Output. Reference numerals 15 and 16 are encoders that output only the sign of the input signal, and output 1 only when the sign is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 20 is an AND gate that outputs 1 only when all three inputs are 1, and outputs 0 otherwise. Reference numeral 21 is an absolute value calculator for calculating the absolute value of the input signal, and 23 is a memory for holding a preset value D.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {x
The code of (k) -x (k-1)} and {x (k + 1) -x
When the signs of (k)} do not match, 1 is output, and when they match, 0 is output. The output of the subtractor 22 is | x
(K) Outputs 1 when | <D and outputs 0 otherwise.
The output of the XOR gate 17 is the sign of x (k) and x
When the signs of f (k) do not match, 1 is output, and when they match, 0 is output. In other words, the output of the AND gate 20 becomes 1 at the time k satisfying | x (k) | <D as shown in FIGS. 21 (a) and 21 (b).
In (k), only the waveform that takes the maximum and the minimum is detected, and the output of the XOR gate 17 becomes 1. Therefore, as shown in (a) and (b) of FIG. The AND gate 20 outputs 1 when it is a waveform and 0 otherwise.

The inversion phenomenon can be detected by the above operation. The waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a), and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 6. Embodiment 6 according to the invention of claim 6
Will be explained. The overall configuration of the inversion phenomenon prevention circuit is as shown in FIG. 1 and the operation thereof is the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 7 is a block circuit diagram of the inversion phenomenon detector of the sixth embodiment. In the figure, 10,
Reference numerals 11 and 12 denote delay devices that delay the input data by one sample clock, and 13, 14 and 24 denote subtractors that output only the sign of the result of subtraction. Set 1 only when the value is negative, and 0 otherwise. Output. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 19 is an AND gate.

The output of the delay corrector 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {x
The code of (k) -x (k)} and {x (k + 1) -x
When the signs of (k)} do not match, 1 is output, and when they match, 0 is output. That is, in x (k) as shown in FIGS. 21 (a) and 21 (b), 1 is output when only the waveform having the maximum and the minimum is detected.
The output of the XOR gate 17 outputs 1 when the code of x (k) and the code of {xf (k) -xf (k-1)} do not match, and outputs 0 when they match. That is,
The output of the AND gate 19 is shown in FIGS.
When the waveform is as shown in, 1 is output, and in other cases, 0 is output.

The inversion phenomenon can be detected by the above operation, and the waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a) and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 7. Embodiment 7 according to the invention of claim 7
Will be explained. The overall configuration of the inversion phenomenon prevention circuit is as shown in FIG. 1 and the operation thereof is the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 8 is a block circuit diagram of the inversion phenomenon detector of the seventh embodiment. In the figure, 10,
Reference numerals 11 and 12 denote delay devices for delaying input data by one sample clock, and 13, 14, 22, and 24 are subtracters for outputting only the sign of the result of subtraction, which is 1 only when the value is negative and otherwise. Outputs 0. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 20 is an AND gate that outputs 1 only when all three inputs are 1, and outputs 0 otherwise. Reference numeral 21 is an absolute value calculator for calculating the absolute value of the input signal, and 23 is a memory for holding a preset value D.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {x
The code of (k) -x (k-1)} and {x (k + 1) -x
When the signs of (k)} do not match, 1 is output, and when they match, 0 is output. The output of the subtractor 22 is | x
(K) Outputs 1 when | <D and outputs 0 otherwise.
The output of the XOR gate 17 outputs 1 when the code of x (k) and the code of {xf (k) -xf (k-1)} do not match, and outputs 0 when they match. That is,
The output of the AND gate 20 becomes 1 because | x (k) |
At time k that satisfies <D, only a waveform that has a maximum and a minimum at x (k) as shown in FIGS. 21A and 21B is detected, and the output of the XOR gate 17 is 1 Therefore, the output of the AND gate 20 outputs 1 when the waveform is as shown in FIGS. 19A and 19B, and 0 otherwise.

The inversion phenomenon can be detected by the above operation. In the case of FIG. 19 (a), the waveform of FIG. 20 (a) is shown, and in the case of FIG. 19 (b), the waveform of FIG. 20 (b) is shown. By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 8. Embodiment 8 according to the invention of claim 8
Will be explained. The overall configuration of the inversion phenomenon prevention circuit is as shown in FIG. 1 and the operation thereof is the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 9 is a block circuit diagram of the inversion detector of the eighth embodiment. In the figure, 10,
Reference numerals 11 and 12 denote delay devices that delay the input data by one sample clock, and 13 and 14 denote subtractors that output only the sign of the result of the subtraction, which outputs 1 only when the number is negative and 0 otherwise. . Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. 1
Reference numerals 7 and 18 are XOR gates, 19 is an AND gate, and 25 is an inverter for inverting an input signal.

The output of the delay corrector 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {xf
The code of (k) -xf (k-1)} and {xf (k + 1)-
When the signs of xf (k)} do not match, 1 is output, and when they match, 0 is output. That is, in xf (k) as shown in FIGS. 18 (a) and 18 (b), 1 is output when only a waveform that takes a maximum and a minimum is detected. The output of the XOR gate 17 is 1 when the result of inverting the sign of x (k) and the sign of {xf (k + 1) −xf (k)} do not match, and 0 when they match. Output. That is, the output of the AND gate 19 is as shown in FIG.
1 is output when the waveforms are as shown in (a) and (b), and 0 is output otherwise.

The inversion phenomenon can be detected by the above operation. In the case of FIG. 19 (a), the waveform of FIG. 20 (a) is shown, and in the case of FIG. 19 (b), the waveform of FIG. 20 (b) is shown. By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 9. Embodiment 9 according to the invention of claim 9
Will be explained. The overall configuration of the inversion phenomenon prevention circuit is as shown in FIG. 1 and the operation thereof is the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 10 is a block circuit diagram of the inversion phenomenon detector of the ninth embodiment. In the figure, 1
0, 11, 12 are delay devices for delaying the input data by one sample clock, and 13, 14, 22 are subtractors for outputting only the sign of the result of the subtraction, which is 1 only when it is negative and at other times. Outputs 0. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 20 is an AND gate that outputs 1 only when all three inputs are 1, and outputs 0 otherwise. Reference numeral 21 is an absolute value calculator for obtaining the absolute value of the input signal, 23 is a memory for holding a preset value D, and 25 is an inverter for inverting the input signal.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {xf
The code of (k) -xf (k-1)} and {xf (k + 1)-
When the signs of xf (k)} do not match, 1 is output, and when they match, 0 is output. The output of the subtractor 22 is
When | x (k) | <D, 1 is output, and otherwise 0 is output. Further, the output of the XOR gate 17 outputs 1 when the sign of x (k) and the result of inverting the sign of {xf (k + 1) −xf (k)} do not match, and outputs 0 when they match. To do. That is, the output of the AND gate 20 becomes 1 at the time k satisfying | x (k) | <D in FIG.
In xf (k) as shown in (a) and (b), only the waveform that takes the maximum and the minimum is detected, and further, the output of the XOR gate 17 becomes 1. The AND gate 20 outputs 1 when the waveforms are as shown in 19 (a) and 19 (b), and 0 otherwise.

The inversion phenomenon can be detected by the above operation, and the waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a), and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 10. A tenth embodiment according to the invention of claim 10 will be described. Figure 1 shows the overall configuration of the inversion prevention circuit.
As described above, the operation is also the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 11 shows Example 1.
It is a block circuit diagram of a 0 inversion phenomenon detector. In the figure, 10, 11, 12, and 26 are delay units that delay input data by one sample clock, and 13, 14, and 24 are subtractors that output only the sign of the result of subtraction. , 0 is output otherwise. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. 17 and 18 are XOR gates, 1
9 is an AND gate, and 25 is an inverter that inverts an input signal.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {x
The code of (k) -x (k-1)} and {x (k + 1) -x
When the signs of (k)} do not match, 1 is output, and when they match, 0 is output. That is, in x (k) as shown in FIGS. 21 (a) and 21 (b), 1 is output when only the waveform having the maximum and the minimum is detected.
The output of the XOR gate 17 outputs 1 when the result of inverting the sign of x (k) and the sign of {xf (k + 1) −xf (k)} do not match, and outputs 0 when they match. To do. That is, the output of the AND gate 19 is as shown in FIG.
1 is output when the waveforms are as shown in (a) and (b), and 0 is output otherwise.

The inversion phenomenon can be detected by the above operation, and the waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a) and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 11. An eleventh embodiment according to the invention of claim 11 will be described. Figure 1 shows the overall configuration of the inversion prevention circuit.
As described above, the operation is also the same as that described in claim 1, and therefore the description thereof is omitted. FIG. 12 shows the first embodiment.
2 is a block circuit diagram of the inversion phenomenon detector of FIG. In the figure, 10, 11, 12, and 26 are delay devices that delay the input data by one sample clock, and 13, 14, 22, and 24 are subtractors that output only the sign of the result of the subtraction. Is output, and 0 is output otherwise. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. Reference numerals 17 and 18 are XOR gates, and 20 is an AND gate that outputs 1 only when all three inputs are 1, and outputs 0 otherwise. Reference numeral 21 is an absolute value calculator for obtaining the absolute value of the input signal, 23 is a memory for holding a preset value D, and 25 is an inverter for inverting the input signal.

The output of the delay compensator 2 in FIG.
-1), the output of the sideband suppression filter 3 is xf (k-1)
And At this time, the output of the XOR gate 18 is {x
The code of (k) -x (k-1)} and {x (k + 1) -x
When the signs of (k)} do not match, 1 is output, and when they match, 0 is output. The output of the subtractor 22 is | x
(K) Outputs 1 when | <D and outputs 0 otherwise.
Further, the output of the XOR gate 17 outputs 1 when the sign of x (k) and the result of inverting the sign of {xf (k + 1) −xf (k)} do not match, and outputs 0 when they match. To do. That is, the output of the AND gate 20 becomes 1 at the time k satisfying | x (k) | <D in FIG.
In x (k) as shown in (a) and (b),
Since only the waveform that takes the maximum and the minimum is detected and the output of the XOR gate 17 becomes 1, eventually, 1 is output when the waveforms shown in FIGS. 19A and 19B are obtained. , Otherwise, the AND gate 20 outputs 0.

The inversion phenomenon can be detected by the above operation, and the waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a) and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 12 A twelfth embodiment according to the invention of claim 12 will be described. Figure 1 shows the overall configuration of the inversion prevention circuit.
3 shows. The only difference from FIG. 1 is that the inversion phenomenon is detected only from the output of the delay compensator 2, and other configurations and operations are the same as those described in claim 1, and therefore the description will be given. A block circuit diagram of the inversion phenomenon detector is omitted and is shown in FIG. In the figure, 10 and 11 are delay units for delaying input data by one sample clock, 1
Subtractors 3 and 14 output only the sign of the result of the subtraction, and output 1 only when the sign is negative and 0 otherwise.
Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. 27, 28,
29 is an inverter for inverting the input signal, 30 and 31 are 3
An AND gate 32 outputs 1 only when all the inputs are 1, and an OR gate 32 outputs 0 otherwise.

There are only two ways in which the output of the OR gate 32 becomes 1, and the first is that the output of the subtractor 13 is 0, the output of the subtractor 14 is 1, and the sign of x (k). Is one. The other one is when the output of the subtractor 13 is 1, the output of the subtractor 14 is 0, and the sign of x (k) is 0. In the former case, x shown in FIG.
There is a positional relationship between the waveform having the maximum in (k) and the waveform of the solid line with respect to the zero level. In the latter case, FIG.
There is a positional relationship between the waveform having the minimum value at x (k) shown by and the waveform of the solid line with respect to the zero level. In other cases, the OR gate 32 outputs 0.

The inversion phenomenon can be detected by the above operation, and the waveform of FIG. 20 (a) is shown in the case of FIG. 19 (a), and the waveform of FIG. 20 (b) is shown in the case of FIG. 19 (b). By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

Example 13 A thirteenth embodiment according to the invention of Claim 13 will be described. Figure 1 shows the overall configuration of the inversion prevention circuit.
3 shows. The only difference from FIG. 1 is that the inversion phenomenon is detected only from the output of the delay compensator 2, and other configurations and operations are the same as those described in claim 1, and therefore the description will be given. Omit it. FIG. 15 shows Example 13.
3 is a block circuit diagram of the inversion phenomenon detector of FIG. In the figure, 10 and 11 are delay devices that delay the input data by one sample clock, and 13, 14 and 22 are subtractors that output only the sign of the result of the subtraction. Outputs 0. Reference numeral 15 is an encoder that outputs only the sign of the input signal, and outputs 1 only when it is negative and 0 otherwise. Reference numeral 21 is an absolute value calculator for obtaining the absolute value of the input signal, 23 is a memory for holding a preset value D,
27, 28, 29 are inverters for inverting the input signal, 3
Reference numerals 0 and 31 are AND gates that output 1 only when all three inputs are 1, and 0 otherwise, and 32 is an OR gate.

There are only two ways that the output of the OR gate 32 becomes 1. The first is the case where the output of the subtractor 13 is 0, the output of the subtractor 14 is 1, and the sign of x (k) is 1. The other one is when the output of the subtractor 13 is 1, the output of the subtractor 14 is 0, and the sign of x (k) is 0. In the former case, x shown in FIG.
There is a positional relationship between the waveform having the maximum in (k) and the waveform of the solid line with respect to the zero level. In the latter case, FIG.
There is a positional relationship between the waveform having the minimum value at x (k) shown by and the waveform of the solid line with respect to the zero level. In all other cases, the OR gate 32 outputs 0. Also, the subtractor 2
The output of 2 outputs 1 when | x (k) | <D, and outputs 0 otherwise. That is, the AND gate 19 becomes 1 at the time k satisfying | x (k) | <D in FIG.
In x (k) as shown in (a) and (b),
Only when the maximum and minimum are taken and the positional relationship with the zero level is as shown in FIG. 19, 0 is output in other cases.

With the above operation, the inversion phenomenon can be detected. In the case of FIG. 19 (a), the waveform of FIG. 20 (a) is shown, and in the case of FIG. 19 (b), the waveform of FIG. 20 (b) is shown. By outputting to the output terminal 6 of No. 1, it is possible to prevent the inversion phenomenon.

In the inventions of claims 2, 4, 5, 7, 9, 11 and 13, whether or not | x (k) | <D is used as the detection means, but D is set in advance. Good results are obtained when the value is set to 1/2 or less of the FM wave amplitude.

In the inventions of claims 2, 4, 5, 7, 9, 11 and 13, whether or not | x (k) | <D is used as the detection means. The same effect can be obtained by setting | xf (k) | <E instead of | <D. However, E is a preset value like D,
Good results can be obtained by setting the amplitude of the FM wave to 1/2 or less.

Further, if the inversion phenomenon prevention circuit according to the inventions of claims 1 to 13 is used, the output terminal 6 is provided at the subsequent stage,
It goes without saying that the same effect can be obtained by connecting an FM demodulator of any type such as a TAN type or a pulse count type.

Furthermore, in the inventions of claims 1 to 13, in place of the delay compensator 2 of FIG. 1, a sideband suppression filter 3 and a filter having the same delay amount in consideration of the characteristics of the transmission system are inserted. The same effect can be obtained.

[0084]

According to the present invention, a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter, the input digital FM signal and the sideband when the AC zero level is used as a reference. By selecting and outputting either the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the discriminator that determines whether or not the signs of the output signals of the suppression filters match. For an FM signal in which the upper sideband and the lower sideband are unbalanced, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur, but the carrier component is small in the detector and the discriminator. At the part where it is determined that the inversion phenomenon occurs, the signal is passed through the carrier suppression filter corresponding to the relatively large carrier component, and the Without causing phenomena, moreover it is possible to obtain an inexpensive circuit scale small device in cost digital FM signal while minimizing the S / N deterioration.

According to the second aspect of the present invention, a detector for detecting that the input digital FM signal is within a preset range and a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter. And the input digital FM signal and the side band depending on the output result of the discriminator that determines whether the sign of the digital FM signal and the output signal of the side band suppression filter match when the AC zero level is used as a reference. By selecting and outputting one of the output signals of the wave suppression filter, an FM signal in which the upper sideband and the lower sideband are unbalanced is directly input to a portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although the digital FM signal is output, the carrier component is relatively increased in the portion where the detector and the discriminator determine that the carrier component is small and causes the inversion phenomenon. By outputting a signal that has passed through a carrier suppression filter corresponding to the above, a digital FM signal that does not cause an inversion phenomenon and that suppresses S / N deterioration as much as possible can be obtained with a device that is inexpensive and has a small circuit scale. You can

According to the third aspect of the present invention, a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter, the output signal of the sideband suppression filter and the signal preceding in time therewith. Of the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the subtraction result and the output result of the discriminator that determines the multiplication result of the subtraction result and the digital FM signal. As a result, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur with respect to the FM signal in which the upper sideband and the lower sideband are unbalanced.
In the part where it is determined that the carrier component is small in the detector and the discriminator to cause the inversion phenomenon, the inversion phenomenon does not occur by outputting the signal passed through the carrier suppression filter corresponding to the relatively large carrier component. , And S /
It is possible to obtain a digital FM signal in which N deterioration is suppressed as much as possible with a device that is inexpensive and has a small circuit scale.

According to the invention of claim 4, a detector for detecting that the input digital FM signal is within a preset range, and a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter. And the subtraction result of the output signal of the sideband suppression filter and the signal that is earlier in time than it,
According to the output result of the discriminator that discriminates the multiplication result of the subtraction result and the digital FM signal, the input digital F
By selecting and outputting either the M signal or the output signal of the sideband suppression filter, the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the upper sideband and the lower sideband are unbalanced. In the portion, the input digital FM signal is output as it is, but in the portion where it is determined that the carrier component is small in the detector and the discriminator and the inversion phenomenon occurs, it is passed through the carrier suppression filter corresponding to the relatively large carrier component. By outputting the signal, it is possible to obtain a digital FM signal in which the inversion phenomenon does not occur and the S / N deterioration is suppressed as much as possible with a low cost and a small circuit scale.

According to the invention of claim 5, a detector for detecting that the input digital FM signal is within a preset range, a detector for detecting a maximum point and a minimum point of the digital FM signal, and an alternating current Depending on the output result of the discriminator that determines whether or not the sign of the digital FM signal and the output signal of the sideband suppression filter match when the zero level is used as a reference, By selecting and outputting one of the output signals, the input digital FM signal is directly input to the FM signal in which the upper sideband and the lower sideband are unbalanced, in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although it is output, in the part where the carrier component is small in the detector and the discriminator and it is judged that the inversion phenomenon occurs, it is possible to increase the carrier component relatively. By outputting a signal through a carrier suppression filter, without causing inversion, moreover it is possible to obtain an inexpensive circuit scale small device in cost digital FM signal while minimizing the S / N deterioration.

According to the sixth aspect of the present invention, the detector for detecting the maximum and minimum points of the input digital FM signal, the subtraction result of the output signal of the sideband suppression filter and the signal preceding it in time. , The subtraction result and the digital FM
By selecting and outputting either the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the discriminator that determines the multiplication result with the signal, the upper sideband and the lower sideband are separated. With respect to a balanced FM signal, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur, but the portion where the carrier component is small in the detector and the discriminator is determined to cause the inversion phenomenon. Then, by outputting a signal that has passed through a carrier wave suppression filter corresponding to a relatively large carrier wave component, a digital FM signal that does not cause an inversion phenomenon and suppresses S / N deterioration as much as possible is inexpensive. Can be obtained with a device having a small circuit scale.

According to the invention of claim 7, a detector for detecting that the input digital FM signal is within a preset range, a detector for detecting a maximum point and a minimum point of the digital FM signal, and a side band. According to the subtraction result of the output signal of the wave suppression filter and the signal preceding in time, and the output result of the discriminator that discriminates the multiplication result of the subtraction result and the digital FM signal, the input digital FM signal is output. By selecting and outputting one of the output signals of the sideband suppression filter, the FM signal in which the upper sideband and the lower sideband are unbalanced is used as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although the input digital FM signal is output, the carrier component is relatively increased in the portion where the detector and the discriminator determine that the carrier component is small and causes the inversion phenomenon. By outputting a signal that has passed through a carrier suppression filter corresponding to the above, a digital FM signal that does not cause an inversion phenomenon and that suppresses S / N deterioration as much as possible can be obtained with a device that is inexpensive and has a small circuit scale. You can

According to the invention of claim 8, a detector for detecting a maximum point and a minimum point of the output signal of the sideband suppression filter, the output signal of the sideband suppression filter and a signal later in time. Of the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the subtraction result and the output result of the discriminator that determines the multiplication result of the subtraction result and the input digital FM signal. As a result, the input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur with respect to the FM signal in which the upper sideband and the lower sideband are unbalanced.
In the part where it is determined that the carrier component is small in the detector and the discriminator to cause the inversion phenomenon, the inversion phenomenon does not occur by outputting the signal passed through the carrier suppression filter corresponding to the relatively large carrier component. , And S /
It is possible to obtain a digital FM signal in which N deterioration is suppressed as much as possible with a device that is inexpensive and has a small circuit scale.

According to the invention of claim 9, a detector for detecting that the input digital FM signal is within a preset range, and a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter. And a subtraction result between the output signal of the sideband suppression filter and a signal that is later in time than that,
According to the output result of the discriminator that discriminates the multiplication result of the subtraction result and the digital FM signal, the input digital F
By selecting and outputting either the M signal or the output signal of the sideband suppression filter, the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the upper sideband and the lower sideband are unbalanced. In the portion, the input digital FM signal is output as it is, but in the portion where it is determined that the carrier component is small in the detector and the discriminator and the inversion phenomenon occurs, it is passed through the carrier suppression filter corresponding to the relatively large carrier component. By outputting the signal, it is possible to obtain a digital FM signal in which the inversion phenomenon does not occur and the S / N deterioration is suppressed as much as possible with a low cost and a small circuit scale.

According to the tenth aspect of the present invention, a detector for detecting the maximum and minimum points of the input digital FM signal,
The subtraction result of the output signal of the sideband suppression filter and the signal that is later in time, the subtraction result, and the digital F
By selecting and outputting either the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the discriminator that determines the multiplication result with the M signal, the upper sideband and the lower sideband are separated. For an unbalanced FM signal, the input digital FM signal is output as it is in a portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur, but it is determined that the carrier component is small and the inversion phenomenon occurs in the detector and the discriminator. In the portion, a signal passed through a carrier suppression filter corresponding to a relatively large carrier component is output, so that the inversion phenomenon does not occur, and the digital FM signal in which the S / N deterioration is suppressed as much as possible is also cost effective. It can be obtained with a device that is inexpensive and has a small circuit scale.

According to the invention of claim 11, a detector for detecting that the input digital FM signal is within a preset range, a detector for detecting a maximum point and a minimum point of the digital FM signal, and a side band. An input digital FM signal is output according to the result of subtraction between the output signal of the wave suppression filter and a signal that is later in time, and the output result of a discriminator that determines the result of multiplication of the subtraction result and the digital FM signal. By selecting and outputting one of the output signals of the sideband suppression filter, the FM signal in which the upper sideband and the lower sideband are unbalanced is used as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur. Although the input digital FM signal is output, the carrier component is relatively large in the portion where the detector and the discriminator determine that the carrier component is small and causes the inversion phenomenon. By outputting a signal that has passed through a carrier suppression filter corresponding to the above, a digital FM signal that does not cause an inversion phenomenon and suppresses S / N deterioration as much as possible can be obtained by a device with a low cost and a small circuit scale be able to.

According to the twelfth aspect of the present invention, the subtraction result of the input digital FM signal, the digital FM signal, and the signal temporally preceding the digital FM signal, and the digital FM signal and the digital FM signal are used. By selecting and outputting either the input digital FM signal or the output signal of the sideband suppression filter according to the output result of the discriminator that determines the subtraction result from the signal that is later in time, the upper sideband wave The input digital FM signal is output as it is in the portion where the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the lower sideband is unbalanced.
In the part where it is determined that the carrier component is small in the detector and the discriminator to cause the inversion phenomenon, the inversion phenomenon does not occur by outputting the signal passed through the carrier suppression filter corresponding to the relatively large carrier component. , And S /
It is possible to obtain a digital FM signal in which N deterioration is suppressed as much as possible with a device that is inexpensive and has a small circuit scale.

According to the thirteenth aspect of the present invention, a detector for detecting that the input digital FM signal is within a preset range, the digital FM signal, the digital FM signal and the digital FM signal In accordance with the output result of the discriminator for discriminating the subtraction result of the previous signal and the subtraction result of the digital FM signal and the signal subsequent in time from the digital FM signal, the input digital F
By selecting and outputting either the M signal or the output signal of the sideband suppression filter, the amplitude of the carrier component is large and the inversion phenomenon does not occur in the FM signal in which the upper sideband and the lower sideband are unbalanced. In the portion, the input digital FM signal is output as it is, but in the portion where it is determined that the carrier component is small in the detector and the discriminator and the inversion phenomenon occurs, it is passed through the carrier suppression filter corresponding to the relatively large carrier component. By outputting the signal, it is possible to obtain a digital FM signal in which the inversion phenomenon does not occur and the S / N deterioration is suppressed as much as possible with a low cost and a small circuit scale.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an inversion phenomenon prevention device according to a first embodiment of the present invention.

FIG. 2 is a block circuit diagram of an inversion phenomenon detector according to the first embodiment.

FIG. 3 is a block circuit diagram of an inversion phenomenon detector according to a second embodiment of the present invention.

FIG. 4 is a block circuit diagram of an inversion phenomenon detector according to a third embodiment of the present invention.

FIG. 5 is a block circuit diagram of an inversion phenomenon detector according to a fourth embodiment of the present invention.

FIG. 6 is a block circuit diagram of an inversion phenomenon detector according to a fifth embodiment of the present invention.

FIG. 7 is a block circuit diagram of an inversion phenomenon detector of embodiment 6 according to the invention of claim 6;

FIG. 8 is a block circuit diagram of an inversion phenomenon detector of embodiment 7 according to the invention of claim 7;

FIG. 9 is a block circuit diagram of an inversion phenomenon detector according to an eighth embodiment of the invention.

FIG. 10 is a block circuit diagram of an inversion phenomenon detector according to a ninth embodiment of the invention.

FIG. 11 is a block circuit diagram of an inversion phenomenon detector according to a tenth embodiment of the invention.

FIG. 12 is a block circuit diagram of an inversion phenomenon detector of Example 11 according to the invention of claim 11;

FIG. 13 is a block circuit diagram showing an inversion phenomenon prevention device of embodiment 12 according to the invention of claim 12;

FIG. 14 is a block circuit diagram of an inversion phenomenon detector according to a twelfth embodiment.

FIG. 15 is a block circuit diagram of an inversion phenomenon detector of embodiment 13 according to the invention of claim 13;

FIG. 16 is a waveform diagram of an FM signal for explaining the operation of the present invention.

FIG. 17 is a waveform diagram of an FM signal for explaining the operation of the present invention.

FIG. 18 is a waveform diagram of an FM signal for explaining the operation of the present invention.

FIG. 19 is a waveform diagram of an FM signal for explaining the operation of the present invention.

FIG. 20 is a waveform diagram of an FM signal for explaining the operation of the present invention.

FIG. 21 is a waveform diagram of an FM signal for explaining the operation of the present invention.

FIG. 22 is a block circuit diagram showing a conventional inversion phenomenon prevention device.

FIG. 23 is a block circuit diagram showing a conventional digitalized inversion phenomenon prevention device.

[Explanation of symbols]

 2 Delay Corrector 3 Sideband Suppression Filter 4 Inversion Phenomenon Detector 5 Selector 10 Delay Device 11 Delay Device 12 Delay Device 13 Subtractor 14 Subtractor 15 Encoder 16 Encoder 17 XOR Gate 18 XOR Gate 19 AND Gate 20 AND Gate 21 Absolute Value Calculator 22 Subtractor 23 Memory 24 Subtractor 25 Inverter 26 Delayer 27 Inverter 28 Inverter 29 Inverter 30 AND Gate 31 AND Gate 32 OR Gate

Claims (13)

[Claims] 1. A sideband suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector that detects an inversion phenomenon.
A reversal phenomenon prevention device comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector is A detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter,
An inversion phenomenon prevention device comprising a discriminator that discriminates whether or not the signs of the digital FM signal and the output signal of the sideband suppression filter match when the AC zero level is used as a reference. . 2. A sideband wave suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector that detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector that detects that the digital FM signal is within a preset range, a detector that detects a maximum point and a minimum point of the output signal of the sideband suppression filter, and a detector that uses the AC zero level as a reference. An inversion phenomenon prevention device comprising a digital FM signal and a discriminator that discriminates whether or not the signs of the output signals of the sideband suppression filters match. 3. A sideband suppression filter which receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector which detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter, the subtraction result of the output signal of the sideband suppression filter and the signal earlier in time, the subtraction result and the digital signal. An inversion phenomenon prevention device comprising a discriminator that discriminates a result of multiplication with an FM signal. 4. A sideband suppression filter which receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector which detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector for detecting that the digital FM signal is within a preset range, a detector for detecting the maximum and minimum points of the output signal of the sideband suppression filter, and an output signal of the sideband suppression filter. An inversion phenomenon prevention device comprising a subtraction result of a signal earlier in time and a discriminator that determines a multiplication result of the subtraction result and the digital FM signal. 5. A sideband suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector that detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector for detecting that the digital FM signal is within a preset range, a detector for detecting the maximum point and the minimum point of the digital FM signal, and the digital FM signal when the AC zero level is used as a reference. An inversion phenomenon prevention device comprising a discriminator that discriminates whether or not the signs of the output signals of the sideband suppression filters match. 6. A sideband wave suppression filter which receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector which detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector for detecting the maximum and minimum points of the digital FM signal, a subtraction result of the output signal of the sideband suppression filter and a signal preceding it in time, and the subtraction result and the digital FM signal. An inversion phenomenon prevention device comprising a discriminator for discriminating a multiplication result. 7. A sideband suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector that detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector for detecting that the digital FM signal is within a preset range, a detector for detecting a maximum point and a minimum point of the digital FM signal, an output signal of the sideband suppression filter, and a time point thereof. 1. An inversion phenomenon prevention device comprising: a subtraction result of the previous signal and a discriminator that discriminates a multiplication result of the subtraction result and the digital FM signal. 8. A sideband suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector that detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector for detecting the maximum point and the minimum point of the output signal of the sideband suppression filter, the subtraction result of the output signal of the sideband suppression filter and a signal temporally later than the output signal, the subtraction result and the digital signal. An inversion phenomenon prevention device comprising a discriminator that discriminates a result of multiplication with an FM signal. 9. A sideband suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, and an inversion phenomenon detector that detects an inversion phenomenon.
A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to the output result of the reversal phenomenon detector, wherein the reversal phenomenon detector comprises: A detector that detects that the digital FM signal is within a preset range, a detector that detects the maximum and minimum points of the output signal of the sideband suppression filter, and an output signal of the sideband suppression filter. An inversion phenomenon prevention device comprising: a subtraction result of a signal that is later in time and a discriminator that determines a multiplication result of the subtraction result and the digital FM signal. 10. A sideband suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, an inversion phenomenon detector that detects an inversion phenomenon, and an inversion phenomenon detector. A reversal phenomenon prevention device comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to an output result, wherein the reversal phenomenon detector has a maximum of the digital FM signal. Of detecting a point and a minimum point, a subtraction result of an output signal of the sideband suppression filter and a signal which is later in time, and a determination result of a multiplication result of the subtraction result and the digital FM signal. An inversion phenomenon prevention device characterized by being configured with a container. 11. A sideband suppression filter for receiving a quantized digital FM signal and suppressing upper and lower sidebands or lower sidebands, an inversion phenomenon detector for detecting an inversion phenomenon, and an inversion phenomenon detector. A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and an output signal of the sideband suppression filter according to an output result, wherein the reversal phenomenon detector is configured to detect the digital FM signal in advance. A detector for detecting that it is within a set range, a detector for detecting the maximum and minimum points of the digital FM signal, an output signal of the sideband suppression filter, and a signal later in time. An inversion phenomenon prevention device comprising a subtraction result and a discriminator for discriminating a multiplication result of the subtraction result and the digital FM signal. 12. A sideband suppression filter that receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, an inversion phenomenon detector that detects an inversion phenomenon, and an inversion phenomenon detector. A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and the output signal of the sideband suppression filter according to an output result, wherein the reversal phenomenon detector includes the digital FM signal, A discriminator for discriminating a subtraction result of the digital FM signal and a signal temporally preceding the digital FM signal and a subtraction result of the digital FM signal and a signal temporally subsequent to the digital FM signal. A reversal phenomenon prevention device characterized by being configured. 13. A sideband suppression filter which receives a quantized digital FM signal and suppresses upper and lower sidebands or lower sidebands, an inversion phenomenon detector for detecting an inversion phenomenon, and an inversion phenomenon detector. A reversal phenomenon prevention apparatus comprising a selector for selecting one of the digital FM signal and an output signal of the sideband suppression filter according to an output result, wherein the reversal phenomenon detector is configured to detect the digital FM signal in advance. A detector for detecting that it is within a set range, the digital FM signal, a subtraction result of the digital FM signal and a signal temporally preceding the digital FM signal, the digital FM signal and the digital FM. An inversion phenomenon prevention device comprising: a discriminator that discriminates a subtraction result from a signal that is later than a signal in time.