JPH05110608A - Fsk data receiver - Google Patents

Abstract

PURPOSE:To obtain the FSK data receiver suitable for circuit integration with an excellent characteristic at a low power consumption by reducing the scale of a high frequency circuit section requiring the power consumption. CONSTITUTION:A carrier signal 1 subject to FSK modulation is converted into a base band signal by a mixer 2 and a reference voltage of the 1st base band signal 4 obtained by a low pass filter 3 is detected by a reference voltage detection circuit 5. A phase of a local oscillation signal is shifted by 0 deg. or 90 deg. by a phase control circuit 7 in response to a 1st phase control signal 6 being an output signal of the circuit 5, and the 1st base band signal 4 and the 1st phase control signal 6 are mixed by a 1st base band mixer 9. Thus, two signals causing a phase lag or lead of 90 deg. in response to the FSK modulation data are obtained and demodulation is easily attained by an orthogonal demodulation circuit or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to frequency shift keying (hereinafter referred to as
The present invention relates to a receiver of a signal converted into FSK (abbreviated as FSK), and more particularly to a direct conversion FSK data receiver suitable for downsizing and low power consumption.

[0002]

2. Description of the Related Art In recent years, the direct conversion method has been used in pager receivers and the like as a method suitable for integration because it allows filtering in the base band, and the phase relationship between two orthogonal channels is used. There is also a method of demodulating from the frequency of the carrier wave signal frequency, and a method of demodulating from the frequency difference of the output signal.
A method has also been proposed in which the phase shift of the local oscillation signal is switched and demodulated (for example, Japanese Patent Laid-Open No. 64-84948).

A conventional direct conversion receiver will be described below. FIG. 9 shows a conventional demodulation method using one mixer.

In FIG. 12, 101 is a frequency converter,
102 is a filter circuit, 103 is a limiter circuit, and 104.
Is an exclusive OR circuit, 105 is a counter circuit, 106 is a shift register circuit, 107 is a switching control circuit, 108 is a 0 ° / 90 ° phase switching circuit, and 109 is a local oscillator.

The operation of the direct conversion receiver configured as described above will be described below.

In the first half of the FSK-modulated 1-bit data, the 0 ° / 90 ° phase switching circuit 108 is set to 0 °,
It is converted into a baseband signal by the frequency converter 101, passes through the filter circuit 102 and the limiter circuit 103,
The waveform is accumulated in the shift register circuit 106. FSK
In the latter half of the modulated 1-bit data, 0 ° / 9
The 0 ° phase switching circuit is set to 90 °, and similarly the frequency conversion circuit 101, the filter circuit 102, and the limiter circuit 103.
The waveform is shaped through. First, the shift register circuit 10
The waveform of the first half of the 1-bit data of the FSK modulated signal stored in 6 is read out after being shifted by 90 ° from the later-written waveform, and the waveform of the latter half of the 1-bit data is read by the exclusive OR circuit 104. Calculate. The output baseband signal is + 90 ° / −9 corresponding to the data of the FSK modulation signal due to the phase change of 0 ° / 90 ° of the local oscillation signal.
Change by 0 °. By reading out the signal waveform accumulated in the shift register circuit 106 by shifting the phase by 90 °,
The signal in which the local signal is switched between 0 ° / 90 ° has an in-phase or anti-phase relationship depending on the data of the FSK modulation signal. Therefore, by taking the exclusive OR of both, "1"
/ "0" can be determined.

[0007]

However, in the above-mentioned conventional configuration, means for synchronizing with the 1-bit data is required to switch the phase of the local oscillation signal between the first half and the latter half of the 1-bit data. In addition, when the frequency deviation of the FSK modulated signal is smaller than the transmission rate, when converted to a baseband signal, the signal period included in 1-bit data becomes small, and the waveforms in the first half and second half of the 1-bit data are reduced. It becomes difficult to take the correlation of. Even if the transmission speed is not high, if the frequency of the local oscillation signal is deviated, the value of 1 in either code of the FSK modulated data
There is a problem that demodulation becomes difficult as in the case where the transmission rate becomes high because the signal period included in the bit data becomes small.

The present invention solves the above-mentioned problems of the prior art. In particular, for a high-frequency circuit that requires power consumption, it is possible to demodulate an FSK signal with a simple circuit configuration, and a baseband signal processing is applied to a transmission data signal. Even if the transmission speed is high without the need for means for synchronizing
It is an object of the present invention to provide an FSK data receiver which can demodulate even when the frequency of a local oscillation signal is shifted and realizes low power consumption.

[0009]

To achieve this object, the present invention uses a mixer to combine a frequency shift keyed carrier signal and a local oscillator signal having a frequency approximately equal to the carrier signal. In an FSK data receiver for converting into a band signal, a reference voltage of the baseband signal is detected, a means for inverting the sign of the output voltage at the time when the reference voltage is detected, and an output signal of the means for detecting the reference voltage A unit for mixing the phase of the local oscillation signal with 0 ° phase shift or 90 ° phase shift, the output of the baseband signal, and the output signal of the reference voltage detection unit in the baseband. A first means for determining a sign from the baseband signal and the mixed signal;
It has a demodulating means.

Further, the phase of the local oscillation signal is shifted by 0 degrees or 90 degrees depending on the means for generating a pulse having a constant time width with respect to the voltage change of the output of the reference voltage detecting means and the sign of the pulse signal. And a means for phase shifting,
The fourth demodulation means performs demodulation from the change in the sign of the baseband signal voltage with respect to the reference voltage at the change point of either or both of the phase shift and the 90 degree phase shift.

[0011]

The present invention has the above-mentioned structure and uses one mixer,
The FSK-modulated carrier signal is converted into a baseband signal, and the phase of the local oscillation signal is shifted by 0 degrees or 90 degrees at the crossing point of the reference voltage of the baseband signal. A crossing point of the reference voltage occurs at a time corresponding to a 90 degree phase, and I / O in quadrature demodulation
A signal in which the Q signal is alternately switched appears as a baseband signal, and the positive / negative of the waveform is determined by the FSK modulation data. By mixing the baseband signal and the phase control signal of the local oscillation signal, the FSK modulation data can be changed. On the other hand, since there is a 90-degree lead or lag relationship, if either of the two signals is delayed by the time corresponding to the 90-degree phase, the two signals will be in phase or in phase depending on the change in the FSK modulation data. Since they are in the opposite phase, they can be easily demodulated by using a conventional orthogonal demodulation circuit or the like. Also,
Without using the quadrature demodulation circuit, the phase of the local oscillation signal is phase-shifted by 0 degrees or 90 degrees at the crossing point of the reference voltage of the baseband signal, and the demodulation can be easily performed from the waveform change of the baseband signal at that time. it can. In addition to the demodulation circuit, by combining the function of determining the frequency of the baseband signal and the demodulation signal of the demodulation circuit,
The frequency deviation of the local oscillation signal and its direction can be detected, and even if there is a frequency deviation of the local oscillation signal, it is possible to reliably demodulate.

[0012]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the FS according to the first embodiment of the present invention.
It is a block diagram of a K data receiver.

In FIG. 1, reference numeral 1 denotes an FSK-modulated carrier signal which is converted into a baseband by a mixer 2, passes through a low pass filter 3 and outputs a first baseband signal 4. Further, the first baseband signal 4 is input to the reference voltage detection circuit 5, and the first phase control signal 6 is output.
Reference numeral 7 is a phase control circuit, which receives an output signal of the local oscillation circuit 8 and inputs the output signal to the mixer 2. Reference numeral 9 denotes a baseband mixer, which receives the first baseband signal 4 and the first phase control signal 6 as input and outputs the second baseband signal 10
Is output. Reference numeral 11 denotes a first demodulation circuit, which receives the first baseband signal 4 and the first phase control signal 6 as inputs,
The first demodulated signal 12 is output.

The operation of the FSK data receiver configured as above will be described with reference to the signal waveforms of the respective parts shown in FIG.

First, the carrier signal 1 FSK-modulated by the transmission data signal (FIG. 2 (a)) is converted into a baseband signal by the mixer 2, passes through the low pass filter 3, and is passed through the first base. Band signal 4 (FIG. 2D) is output. For example, if the reference voltage of the reference voltage detection circuit 5 is 0V, the zero-voltage crossing point (zero crossing point) of the first baseband signal 4 is detected by the reference voltage detection circuit 5, and at the time when the zero-crossing point is detected, the output signal The voltage of the first phase control signal 6 (FIG. 2 (e)) is changed. Since the reference voltage detection circuit 5 may detect a zero-cross point that should not be originally detected due to noise due to phase switching, a time delay of phase switching, or the like, in such a case, immediately after detecting the zero-cross point. It is necessary to stop the detection function only for a certain period.

The phase control circuit 7 includes a first phase control signal 6
The phase of the output signal of the local oscillation circuit 8 is set to 0 according to the voltage of
The phase shift is switched to the 90 degree phase shift. The baseband mixer 9 mixes the first baseband signal 4 and the output signal of the first phase control signal 6, and the second baseband signal 10 is mixed.
(FIG. 2 (f)) is obtained.

The I and Q signals in FIGS. 2 (b) and 2 (c) are
It is a baseband signal when conventional quadrature demodulation is performed. In the present embodiment, when the I / Q signals are alternately switched according to the sign of the first phase control signal 6, the next zero cross is basically generated at the time corresponding to the next 90 degree phase. However, a waveform whose positive / negative is determined by the FSK modulation data appears as the first baseband signal 4. FSK
When the modulation data is "1", the second baseband signal 10 is compared with the first baseband signal 4 by the I /
The waveform remains delayed for a time corresponding to the 90-degree phase of the Q signal. Also, the FSK modulation data is "0".
In this case, the waveform of the second baseband signal 10 is advanced with respect to the first baseband signal 4 for the time corresponding to the 90-degree phase of the I / Q signal. In this way, the phase relationship between the two signals changes to +90 degrees or -90 degrees depending on "1" and "0" of the FSK modulated data, and therefore both signals are I / Q when performing conventional quadrature demodulation. Similar to the signals, if one of the signals is delayed by 90 degrees, it becomes in-phase or anti-phase depending on the FSK modulation data. Therefore, it is possible to demodulate by mixing either one of the two signals with a delay of 90 degrees.
Therefore, as the first demodulation circuit 11, almost any circuit can be applied as long as it is a circuit that performs conventional quadrature demodulation.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows the FS in the second embodiment of the present invention.
It is a K data receiver block block diagram.

In FIG. 3, 13 is a limiter amplifier,
The first baseband signal 4 is input and the third baseband signal 14 is output. 15 is an exclusive OR circuit,
The third baseband signal 14 and the first phase control signal 6
Is input and the fourth baseband signal 16 is output.
Reference numeral 11 denotes a first demodulation circuit, which is a third baseband signal 14
And the fourth baseband signal 16 are input. FIG. 4 is a diagram showing the waveform of each part of the FSK data receiver in the second embodiment. The difference from the first embodiment is that the mixing of the baseband signal and the first phase control signal 6 is performed by an exclusive OR with a digital signal instead of an analog signal.

The operation of the FSK data receiver configured as above will be described with reference to the signal waveforms of the respective parts shown in FIG.

First, as in the first embodiment, the carrier wave signal FSK-modulated by the transmission data signal (FIG. 4A) is mixed by the mixer 2 into the first baseband signal 4 (FIG. 4B).
And the phase of the local oscillation signal is switched at the zero crossing point of the first baseband signal 4. The first baseband signal 4 is amplitude-limited by the limiter amplifier 13, and the first baseband signal 14 is a first phase control signal which is an output signal of the reference voltage detection circuit 5 as a third baseband signal 14 (FIG. 4D). 6 (FIG. 4 (c)) and the exclusive OR circuit 15 perform mixing to obtain a fourth baseband signal 16 (FIG. 4 (e)).
Is output. Similar to the first embodiment, the third baseband signal 14 and the fourth baseband signal 16 have a phase lead or lag relationship in accordance with the FSK modulation data. Also, the first demodulation circuit 11 can easily demodulate even by 90-degree phase shift.

FIG. 5 shows a circuit configuration of the first demodulation circuit 11 which is a main part of the FSK data receiver in this embodiment.

Reference numeral 17 denotes a 90-degree phase shift circuit, which shifts the third baseband signal 14 by 90 degrees, and an exclusive OR circuit 18,
The exclusive OR with the fourth baseband signal 16 is obtained and output. The 90-degree phase shift circuit 17 uses the first phase control signal 6
Can be easily realized by the shift register circuit using the clock signal as a clock signal. The phase relationship between the signal obtained by shifting the third baseband signal 14 by 90 degrees and the fourth baseband signal 16 is in-phase or anti-phase depending on the sign of the FSK modulated data. Therefore, the sign can be easily determined by taking the exclusive OR of the two. By thus shaping the waveform of the baseband signal and converting it into a digital signal, it is possible to easily shift the phase by 90 degrees.

In the present embodiment, the third baseband signal 14 is shifted by 90 degrees, but it goes without saying that the side of the fourth baseband signal 16 may be shifted by 90 degrees. ..

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 shows the FS in the third embodiment of the present invention.
2 shows a circuit configuration of a first demodulation circuit of a K data receiver.

In FIG. 6, reference numeral 19 denotes a 90-degree phase shift circuit, which shifts the fourth baseband signal 16 by 90 degrees and mixes it with the original signal by the second baseband mixer 20. Further, the third baseband mixer 21 mixes the output signal of the second baseband mixer 20 and the first phase shift control signal 6. The difference from the second embodiment is that the frequency of the fourth baseband signal 16 is doubled by using a 90-degree phase shift circuit and a mixer. In the present embodiment, the second baseband mixer 20 and the third baseband mixer 21.
The exclusive OR circuit is used as.

The operation of the first demodulation circuit of the FSK data receiver configured as above will be described. 9
The 0 degree phase shift circuit 19 causes the fourth baseband signal 16
By 90 degrees and by taking the exclusive OR with the signal before the 90 degree phase shift, the output signal has a frequency twice that of the fourth baseband signal 16. Further, this signal has an in-phase or anti-phase relationship with the first phase control signal 6 according to the FSK modulation data, so that by mixing the both signals by the third baseband mixer 21, Can be demodulated.

In the conventional quadrature demodulation system, one of the I / Q signals is phase-shifted by 90 degrees, and the other is 90 degrees.
A method has been proposed in which a signal having a frequency doubled is mixed with a signal before being phase-shifted, and a signal obtained by mixing I / Q signals is mixed to perform demodulation. In this embodiment, a signal equivalent to the I / Q signal is set to 1
Since it can be generated by one mixer, and the same signal as the signal obtained by mixing the I / Q signals can be obtained by using the first phase control signal 6, the circuit configuration becomes simpler than the conventional one.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings.

FIG. 7 shows the FS in the fourth embodiment of the present invention.
It is a K data receiver block block diagram.

In FIG. 7, 11 is the first demodulated signal 12
Is a first demodulation circuit that outputs the first phase control signal 6, and 22 is a frequency determination circuit that uses the first phase control signal 6 as an input signal. The output signal is input to the control signal generation circuit 23 and outputs the first control signal 24. .. A second demodulation circuit 25 receives the output signal of the frequency determination circuit 22 and the first demodulation signal 12, and outputs a second demodulation signal 26. A demodulation signal processing circuit 27 receives the first control signal 24, the second demodulation signal 26, and the first demodulation signal 12 and outputs the third demodulation signal 28.

The operation of the FSK data receiver configured as described above will be described. When the carrier signal frequency and the local oscillation signal frequency are deviated from each other, the FSK modulation data causes the baseband signal frequency to have a high or low value, and equivalently, a high modulation index state and a low modulation index state appear. Example 2
In the first demodulation circuit 11 of the third embodiment, the reliability of the demodulated signal becomes poor when the equivalent modulation index is low. Since the first phase control signal 6 has a frequency twice that of the baseband signal, the frequency can be determined by inputting it to the frequency determination circuit 22. A control signal generation circuit 2 is generated by a signal from the frequency determination circuit 22.
At 3, the local oscillation frequency deviation is determined and the first control signal 24 is obtained. According to the first control signal 24, in the case where the local oscillation frequency deviation is small, the decoded signal processing circuit 2
In step 7, the first demodulation circuit 11 determines whether the frequency shift of the FSK modulation frequency signal is up or down, and attaches importance to the first demodulation signal 12 and outputs the third demodulation signal 28.

When the local oscillation frequency shift becomes large to some extent, the change in the frequency shift of the FSK modulation data can be determined from the level of the output voltage of the frequency determination circuit 22. Further, the direction in which the local oscillation signal is deviated can be determined from the relationship between the output signal of the frequency determination circuit 22 and the in-phase and anti-phase of the first demodulation signal 12. That is, the second demodulation circuit 25 detects the direction of the frequency deviation of the local oscillation signal, and the output signal of the frequency determination circuit 22 is inverted or non-inverted depending on the direction of the frequency deviation, whereby the second demodulation is performed. A signal 26 is obtained, and the demodulation signal processing circuit 27
The first demodulated signal 12 and the second demodulated signal 26 output the third demodulated signal 28.

As described above, a method of demodulating in combination with a frequency determination circuit has been proposed by utilizing the fact that the baseband signal frequency becomes high or low when the local oscillation signal is deviated. By performing the frequency determination using the first phase control signal 9, which is twice the frequency of the baseband signal, instead of determining the frequency of the baseband signal, the frequency determination by pulse count or the like becomes easy. ..

(Fifth Embodiment) A fifth embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 shows the FS in the fifth embodiment of the present invention.
It is a K data receiver block block diagram.

In FIG. 8, the fifth baseband signal 29 obtained by converting the FSK-modulated carrier signal 1 into the baseband by the mixer 2 and the low-pass filter 3 is input to the reference voltage detection circuit 5, and the reference voltage is detected. The output signal of the voltage detection circuit 5 is input to the pulse generation circuit 30, and the second phase control signal 31 which is the output signal thereof is input to the phase control circuit 7 and the fourth demodulation circuit 32. On the other hand, the fifth baseband signal 29 passes through the limiter amplifier 13 and is input to the fourth demodulation circuit 32 as the sixth baseband signal 33.
Further, the fourth demodulation circuit 32 outputs a fourth demodulation signal 34. That is, the difference from the first and second embodiments is that
The point is that a pulse having a constant pulse width is generated at the zero-cross point of the baseband signal, and control is performed only during that period to switch the phase of the local oscillation signal.

The operation of the FSK data receiver configured as above will be described with reference to the signal waveforms of the respective parts shown in FIG.

First, the carrier signal 1 FSK-modulated by the transmission data signal (FIG. 9A) is converted into the fifth baseband signal (FIG. 9D) by the mixer 2, and the fifth baseband signal is obtained. At the zero-cross point of the band signal, the second phase control signal 31 (FIG. 9) output by the pulse generation circuit 30.
Only during the pulse width period of (e)), the phase of the local oscillation signal is switched. Further, the fifth baseband signal 29 is shaped into a rectangular wave by the limiter amplifier 13 and becomes a sixth baseband signal 33 (FIG. 9 (f)).

The I and Q signals shown in FIGS. 9 (b) and 9 (c) are signals for performing conventional quadrature demodulation, and are signals whose I / Q is switched by the sign of the second phase control signal 31. Becomes the fifth baseband signal 29. When the FSK modulation data is "1", the code of the sixth baseband signal 33 before and after the pulse of the second phase control signal 31 rises is the same code, and the FSK modulation data is "0". In the case of, on the contrary, the sign of the sixth baseband signal 33 is the opposite sign. In this way, demodulation can be performed by determining whether or not there is a sign change in the sixth baseband signal 33 before and after the rising edge of the second phase control signal 31.

FIG. 10 shows a circuit configuration of the fourth demodulation circuit 32 which is a main part of the FSK data receiver in this embodiment.

In FIG. 10, 35 is a delay circuit for the sixth baseband signal 33, 36 is an exclusive OR circuit for mixing the sixth baseband signal 33 and the output of the delay circuit 35, and 37 is an exclusive logic. The output of the summing circuit 36 and the second
And the phase control signal 31 of the D flip-flop. The output of the exclusive OR circuit 36 outputs "1" when the sign is inverted within the delay time τ of the delay circuit 35, and outputs "0" otherwise. D flip-flop 3
By inputting the second phase signal 31 to the clock of 7 and inputting the output signal of the exclusive OR circuit 36 to the data of the D flip-flop 37, a sixth phase signal is generated before and after the rising edge of the second phase control signal 31. The presence or absence of a code change of the baseband signal 33 can be discriminated, and demodulation can be performed.

In the fifth embodiment, although the phase of the local oscillation signal is switched at the zero cross point of the fifth baseband signal 29, the falling edge of the sixth baseband signal 33 is detected, At that point, the phase of the local oscillation signal may be switched. In this case, it is possible to demodulate only from the code of the sixth baseband signal 33 immediately after switching the phase. Further, it goes without saying that demodulation can be performed from the code of the sixth baseband signal 33 by switching the phase not at the falling edge but at the rising edge.

(Embodiment 6) A sixth embodiment of the present invention will be described below with reference to the drawings.

FIG. 11 shows F in the sixth embodiment of the present invention.
It is a SK data receiver block block diagram.

In FIG. 11, 32 is the fourth demodulated signal 3
A fourth demodulation circuit that outputs 4 is a pulse number determination circuit that receives the second phase control signal 32 as an input signal. The output signal is input to the control signal generation circuit 23 and the second control signal 39 is output. Output. A fifth demodulation circuit 40 receives the output signal of the pulse number determination circuit 38 and the fourth demodulation signal 34 and outputs a fifth demodulation signal 41. A demodulation signal processing circuit 24 receives the second control signal 39, the fifth demodulation signal 41, and the fourth demodulation signal 34, and outputs the sixth demodulation signal 42. The difference from the fourth embodiment is that a pulse number determination circuit 38 is provided instead of the frequency determination circuit 22, and a fourth demodulation circuit 3 is provided instead of the first demodulation circuit 11.
2 is that the fifth demodulation circuit 40 is used instead of the second demodulation circuit 25. In this embodiment, as the baseband frequency determining means, the pulse number determining circuit 3 is used.
8, the frequency is determined from the number of pulses of the second phase control signal 32.

Although the phase of the local oscillation signal is switched to 0 degree phase shift or 90 degree phase shift in any of the embodiments, it may be changed to 0 degree phase shift or 90 degree phase shift by phase modulation. It goes without saying that it is good.

Further, in any of the embodiments, the FSK-modulated signal is used as the carrier signal modulation method. However, the FSK-modulated modulated signal obtained by superimposing a sine wave on the baseband signal is used. However, it is apparent that the data demodulation method of the present invention can be applied to a signal format in which the demodulation can be performed without any problem and the modulation is equivalently performed by the frequency shift.

In any of the embodiments, the receiving system is
The case where the direct conversion reception system is used has been described, but if the carrier signal is an intermediate frequency signal,
It is clear that the data receiving method of the present invention can be applied as the heterodyne receiving method.

[0053]

As described above, according to the present invention, the FSK-modulated signal is controlled from one mixer by controlling the phase of the local oscillation signal, so that the I / Q signal in the conventional quadrature demodulation system can be obtained. , It is possible to generate two signals having a phase lead or lag relationship of 90 degrees according to the FSK modulation data, and it is possible to drastically reduce the high frequency circuit part that requires a lot of power consumption, and at the time of demodulation. Since it is possible to easily demodulate with a conventional quadrature demodulation circuit without requiring a means for synchronizing with transmission data, a signal processing circuit in a baseband can be easily configured, thereby achieving miniaturization and low power consumption. The effect is great above.

[Brief description of drawings]

FIG. 1 is a block connection diagram of an FSK data receiver according to a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram of essential parts showing the operation of the FSK data receiver in the first embodiment of the present invention.

FIG. 3 is a block connection diagram of an FSK data receiver according to a second embodiment of the present invention.

FIG. 4 is a signal waveform diagram of essential parts showing the operation of the FSK data receiver in the second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a first demodulation circuit which is a main part of an FSK data receiver according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing a first demodulation circuit which is a main part of an FSK data receiver according to a third embodiment of the present invention.

FIG. 7 is a block connection diagram of an FSK data receiver according to a fourth embodiment of the present invention.

FIG. 8 is a block connection diagram of an FSK data receiver according to a fifth embodiment of the present invention.

FIG. 9 is a signal waveform diagram of essential parts showing the operation of the FSK data receiver in the fifth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a fourth demodulation circuit which is a main part of an FSK data receiver according to a fifth embodiment of the present invention.

FIG. 11 is a block connection diagram of an FSK data receiver according to a sixth embodiment of the present invention.

FIG. 12 is a block connection diagram of a conventional FSK data receiver with phase switching.

[Explanation of symbols]

 1 Carrier wave signal 2 Mixer 3 Low pass filter 4 Reference voltage detection circuit 7 Phase control circuit 8 Local oscillation circuit 9 1st baseband mixer 11 1st demodulation circuit 12 1st demodulation signal 13 Limiter amplifier 15 Exclusive OR circuit 17, 1990 90 degree phase shift circuit 20 Second baseband mixer 21 Third baseband mixer 22 Frequency determination circuit 23 Control signal generation circuit 24 First control signal 25 Second demodulation circuit 26th 2 demodulated signal 27 demodulated signal processing circuit 28 third demodulated signal 30 pulse generation circuit 32 fourth demodulated circuit 34 fourth demodulated signal 38 pulse number determination circuit 39 second control signal 40 fifth demodulated circuit 41 5 demodulated signal 42 sixth demodulated signal 101 frequency converter 102 filter circuit 103 limiter circuit 104 exclusive OR circuit 106 Shift register circuit 108 0/90 ° phase switching circuit 109 Local oscillator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yomi Imagawa 2-45, Hikosancho, Kanazawa, Ishikawa Prefecture Matsushita Communication Kanazawa Research Institute

Claims (17)

[Claims] 1. A frequency shift keyed carrier signal, and a local oscillator circuit having a frequency substantially equal to the carrier signal.
A mixer that mixes the output signal of the local oscillator circuit and the carrier wave signal to convert into a baseband signal and a reference voltage of the baseband signal is detected, and the output signal of the output signal is detected at the time when the reference voltage is detected. Between the reference voltage detection circuit for changing the voltage, the local oscillation circuit and the mixer, the output signal of the reference voltage detection circuit shifts the phase of the output signal of the local oscillation circuit by 0 degree or 90 degrees. Of a phase control circuit, a first baseband mixer that mixes the output of the baseband signal, and an output of the reference voltage detection circuit, the baseband signal, and the first baseband mixer An FSK data receiver having a first demodulation circuit that demodulates from an output signal. 2. The FSK data receiver according to claim 1, wherein the reference voltage of the reference voltage detection circuit is zero voltage. 3. The FSK data receiver according to claim 1, wherein the voltage of the output signal of the reference voltage detection circuit has a binary voltage signal which is inverted every time the reference voltage is detected. 4. A reference voltage detection circuit for a fixed time from the time when the reference voltage of the baseband signal is detected,
The FSK data receiver according to claim 1, further comprising a reference voltage detection unit that stops the function of detecting the reference voltage. 5. The F according to claim 1, further comprising, as the phase control circuit, phase switching means for switching the phase of the output signal of the local oscillator circuit to 0 degree phase shift or 90 degree phase shift.
SK data receiver. 6. The FSK data according to claim 1, further comprising, as the phase control circuit, phase modulation means for phase-modulating the phase of the output signal of the local oscillator circuit to 0 degree phase shift or 90 degree phase shift. Receiving machine. 7. An amplitude limiting amplifier circuit for limiting the amplitude of a baseband signal and an exclusive OR of an output signal of the amplitude limiting amplifier circuit and an output signal of a reference voltage detecting circuit as a first baseband mixer. And an exclusive OR circuit that takes
The FSK data receiver according to claim 1, further comprising a first demodulation circuit that performs demodulation based on a phase relationship between an output signal of the amplitude limiting circuit and an output signal of the exclusive OR circuit. 8. A baseband signal or an output signal of the first baseband mixer is used as the first demodulation circuit.
2. The FSK data receiver according to claim 1, further comprising a 90-degree delay unit for delaying by 90 degrees. 9. A baseband signal or an output signal of the first baseband mixer is used as the first demodulation circuit.
The FSK data receiver according to claim 1, further comprising a 90-degree phase shifting means for shifting the phase. 10. A first demodulation circuit for mixing a baseband signal and a signal obtained by delaying the baseband signal by 90 degrees, or an output signal of a first baseband mixer and the first baseband. A second baseband mixer for mixing the output signal of the mixer with a 90 degree delayed signal;
A third baseband mixer for mixing the output signal of the second baseband mixer and the output signal of the reference voltage detection circuit is provided, and data decoding is performed from the output signal of the third baseband mixer. F according to claim 1, characterized in that
SK data receiver. 11. A first control using a frequency determining circuit for an output signal of a reference voltage detecting circuit and a signal from the frequency determining circuit, in addition to the first demodulating circuit which uses the first demodulated signal as an output signal. A control signal generation circuit that obtains a signal, the first demodulated signal, and the output signal of the frequency determination circuit, by determining the in-phase and in-phase relationship with the output signal of the frequency determination circuit, from the inverted or non-inverted signal of the output signal Or a second demodulation circuit that obtains a second demodulation signal from the output signal of the first demodulation circuit, and outputs the first demodulation signal from the first and second demodulation signals in accordance with the first control signal. The third demodulated signal is obtained to obtain the third
The FSK data receiver according to claim 1, wherein data decoding is performed using the demodulated signal of. 12. A frequency shift-modulated carrier signal and a local oscillation circuit having a frequency substantially equal to that of the carrier signal, wherein the local oscillation signal which is the output signal of the local oscillation circuit and the carrier signal are mixed. Then, a mixer for converting into a baseband signal, a reference voltage detection circuit for detecting a reference voltage of the baseband signal, and a pulse of a constant time width with respect to a voltage change of the output of the reference voltage detection circuit A pulse generator circuit, a phase control circuit for shifting the phase of the local oscillation signal by 0 degrees or 90 degrees depending on the sign of the output signal of the pulse generation circuit, and either the 0 degree phase shift or the 90 degree phase shift. And a fourth demodulation circuit that demodulates from a sign change of the baseband signal voltage with respect to the reference voltage at one or both change points.
Data receiver. 13. The FSK data receiver according to claim 12, further comprising, as the phase control circuit, a phase switching means for switching the phase of the local oscillation signal to 0 degree phase shift or 90 degree phase shift. 14. The F according to claim 12, further comprising, as the phase control circuit, a phase modulation means for performing phase modulation on the phase of the local oscillation signal by 0 degree phase shift or 90 degree phase shift.
SK data receiver. 15. The reference voltage detection circuit has a reference voltage detection means for stopping the function of detecting the reference voltage for a fixed time from the time when the reference voltage of the baseband signal is detected. Item 12. The FSK data receiver according to item 12. 16. A fourth demodulation circuit, wherein a phase control circuit shifts the local oscillation signal from 0 degree phase shift to 90 degree phase shift or 9 degree shift.
The demodulation is performed by determining whether the sign of the reference voltage of the baseband signal before and after changing from 0 ° phase shift to 0 ° phase shift is the same sign or the opposite sign. 12. The FSK data receiver according to item 12. 17. In addition to the fourth demodulation circuit which outputs the fourth demodulation signal as an output signal, a second control signal is generated by a pulse number determination circuit of a pulse generation circuit and a signal from the pulse number determination circuit. The control signal generation circuit to be obtained, the fourth demodulated signal, and the output signal of the pulse number determination circuit, the determination of the in-phase and in-phase relationship with the output signal of the pulse number determination circuit from the inverted or non-inverted signal, Or a fifth demodulation circuit for obtaining a fifth demodulation signal from the output signal of the fourth demodulation circuit,
6. A sixth demodulation signal is obtained from the fourth and fifth demodulation signals according to the second control signal, and data decoding is performed using the sixth demodulation signal. 12
The described FSK data receiver.