JPS61191128A - Noise detector for receiver - Google Patents

Abstract

PURPOSE:To detect a noise only having a large amplitude and short duration time by providing a comparison circuit comparing the output of an amplifier circuit with the 2nd reference value slightly larger than the 1st reference value and outputting a noise detection output when the amplified output exceeds the 2nd reference value. CONSTITUTION:A multi-path distortion component is extracted by an HPF 31 from an input signal (a) superimposed with multi-path distortion and led to a variable gain amplifier 32. The output of the amplifier 32 is subject to envelope detection by a detector 33, inputted to a comparator 37 via an integration device 36 and compared with a reference voltage Vr+Vx. In this case, since the multi-path distortion with a large amplitude like the signal (a) exceeds the voltage Vr+Vx in the detected output of the detector 33, the noise detection signal Sd is outputted. The signal Sd is inputted also to a monostable multivibrator 38 and when a trigger is given to the vibrator 38 within a prescribed time, the output is being sent, then a noise detection signal St having a time width over the period of generation of multi-path distortion is sent.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Application Field The present invention relates to a noise detection device for a receiver. The noise detection device of the present invention is used to detect noise such as vehicle noise, urban noise, and multipath noise generated in a single frequency modulation (FM) stereo receiver. , [Prior Art] ≠Noises generated in a receiver include, for example, vehicle noise, city noise, and multipath distortion in an FM stereo receiver. Multipath distortion is generally caused by interference between direct waves of radio waves and reflected waves reflected from buildings, etc. This multipath distortion appears in the demodulated signal, superimposing the sound quality and causing signal loss.・ ・ Conventionally, there are various methods known to remove such noises such as multipath distortion, and in order to remove them, a device for detecting these noises is required.

FIG. 2 shows a conventional noise detection device. The device shown in Fig. 2 is for detecting multipath distortion in an FM receiver, and the composite signal output from the FM tuner 11 is passed through a high-pass filter with a new station wave number of 60 kHz or higher. It is configured to be guided to a detector 12.

The device shown in Figure 2 focuses on the fact that the high-frequency components (frequency components higher than the modulation component) in the composite signal increase when multipath interference occurs, and extracts the high-frequency components with a high-pass filter, and also uses a detector to extract the high-frequency components. 13 to detect multipath distortion.

FIG. 3 shows another conventional type of noise detection device. Third
The device shown in the figure is also for detecting multipath distortion in an FM receiver, and is configured to guide left and right channel signals output from an FM tuner 11 to a detector 15 via a capacitor 14. This device focuses on the fact that when multipath distortion occurs, the pilot carrier increases and undergoes amplitude modulation at the frequency period of the R channel signal, and detects the low frequency AM component (several hundred Hz to several kHz) of this Byron 1-carrier. It is something to do.

[Problem to be solved by the invention] When removing noise, for example, removing multipath distortion in an FM receiver, it is necessary to perform noise removal processing on the demodulated output during the period of noise detected by the noise detection device. However, if this time continues for a long time, for example, several msec or more, the reproduced sound will have a sense of interruption, so it is necessary to keep the maximum time to several msec or less.

On the other hand, in the case of multipath distortion, for example, as shown in Figure 4, the distortion superimposed on the detection output is caused by repeated large-amplitude and severe distortion parts, and the distortion in the parts in between has a small amplitude. . The duration of the distortion part with large amplitude is 1~
Although it is about several m5EIC, the duration of the part where this occurs repeatedly is several hundred m5ec. Therefore, it is desirable for the noise detection device to detect only the portion where the distortion amplitude is large and perform noise removal processing.

However, conventional noise detection devices only assume that noise is detected when the magnitude of the noise detection output exceeds a certain threshold, so in places where the received electric field is relatively high, the noise level is generally low. However, there is a problem that noise detection is not performed in places where the received electric field is low.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a noise detection device for a receiver that can detect only noises having large amplitudes and relatively short durations from a series of noises.

[Means for solving problems]

In order to solve the above-mentioned problems, the receiver noise detection device of the present invention includes an extraction circuit that extracts a high-frequency noise circuit using a filter from the detection output of the receiver, and a high-frequency noise component extracted by the extraction circuit. a variable gain control type amplifier circuit that amplifies the output of the amplifier; an integration circuit that time-integrates and smoothes the amplified output of the amplifier circuit; and a differential output that compares the integrated output of the integration circuit with a predetermined first reference value a control means for controlling the gain of the amplification circuit accordingly; and a control means for comparing the amplification output of the amplification circuit with a second reference value that is slightly larger than the first reference value; Comparing means is provided for outputting a noise detection output when the value exceeds the value.

[For production]

The high-frequency noise component extracted by the extraction circuit is amplified by an amplifier circuit, then time-integrated by an integration circuit, and guided to a control circuit, where it is compared with a first reference value and a difference therebetween is determined. The gain of the amplifier circuit is variably controlled to increase if the difference is negative, and to decrease if the difference is positive.

Therefore, the amplitude level of the noise is always amplified to an appropriate level at the output of the amplifier circuit.

The output of the amplifier circuit is further led to a comparison circuit and compared with a second reference value, and if this reference value is exceeded, a noise detection signal is output. Since the second reference value is set slightly larger than the first reference value, if the width of the input noise tail is approximately constant over time, the output of the amplifier circuit will be approximately equal to the first reference value. Since they are the same, no detection signal is output from the comparison circuit, and only a sudden noise portion with a large amplitude value included in the noise is detected and output.

〔Example〕

A receiver noise detection apparatus as an embodiment of the present invention will be described below. FIG. 5 shows an example in which the present invention is applied to an FM stereo receiver.

In Figure 5, the radio waves received by antenna AT are FM
Guided to tuner 1. FM tuner 1 is a tuning circuit, T
It consists of an F amplifier and a detection stage, and outputs a composite signal. This composite signal is input to multiplexer 2 and noise detection circuit 3. The multiplexer 2 is a circuit that separates and outputs the composite signal into a right channel signal and a left channel signal, and the right channel signal and left channel signal are respectively sent to the right channel noise removal circuit 4(r).
and the left channel noise removal circuit 4(1).

The noise detection circuit 3 outputs noise detection signals S (d) and S (
tl are guided to the noise removal circuit 4(r) and S_Fil, respectively.

The noise detection circuit 3 as an embodiment of the present invention in FIG. 5 is shown in FIG. In Fig. 1, the composite signal from FM tuner 1 has a blocking wave number of 100k.
A high-frequency noise component is extracted by a high-pass filter 31 of Hz, and the noise component is guided to a detector 33 via a variable gain amplifier 32 . One side of the detection output of the detector 33 is guided to one terminal of the differential amplifier 35 via the integrator 34, and
The other end is led to one terminal of a comparator 37 via an integrator 36.

The integrator 34 and the integrator 36 each consist of a low-pass filter consisting of a resistor and a capacitor, and the time constant τ(1) of the integrator 34 is several m5eC1, and the time constant τ(2) of the integrator 36 is Q , lms, ec.

A reference voltage V (rl) is led to the other terminal of the differential amplifier 35, and the differential amplifier 35 has an integrated output voltage V f
The difference value between pl and the reference voltage V frl is calculated and output. The differential output is directed to a control input terminal of variable gain amplifier 32. The variable gain amplifier 32 has an integrated output voltage (ρ)
If it is larger than the reference voltage V (rl, the gain is lowered, and if it is smaller than the reference voltage V (rl), the gain is increased.

The other terminal of the comparator 37 has a reference voltage V (rl +
V Txl is derived. V (X) is chosen to be slightly larger than V (r). The output of the comparator 37 is used as the noise detection signal S (d) by the noise removal circuit (r), (1
1 and monostable multivibrator 38
guided by. The monostable multi-bi break 38 is for outputting a noise detection signal S(tl) which is output over a period when the detection signal S(dl is continuously outputted).

The operation of the apparatus of FIG. 1 will now be described with reference to FIG. FIG. 6 is a diagram of signal waveforms at various parts, (a) is the input signal waveform on which multipath distortion is superimposed, and (b) is the waveform of the comparator 3.
The detection signal S (d1 waveform) of the output of 7, (C1 is the detection signal S (tl waveform) of the output of the monostable multi-bi break 38.

It is assumed that multipath distortion is superimposed on the composite signal output from the FM tuner 1 as shown in FIG. 6(a). Since this multipath distortion component is a high-frequency component, it is extracted by a high-pass filter 31 and guided to a variable gain amplifier 32. The output of the variable gain amplifier 32 is envelope-detected by a wave detector 33 and input to integrators 34 and 36, respectively.

The integrator 34 time-integrates the detection output and smoothes it, and outputs the integrated output V (pl) to the differential amplifier 35. The differential amplifier 35 compares the integrated output V (ρ) with the reference voltage V (rl 75, Then, the difference value is sent as a control input to the variable gain amplifier 32.As a result, the variable gain amplifier 32 lowers the gain if the noise component from the high-pass filter 31 is too large, and lowers the gain if it is too small. Automatic gain control is performed so that the amplified output is approximately constant over time.

The detection output of the detector 34 is further passed through the integrator 36 as follows:
Input to the comparator 37 and 1. Reference voltage V (rl +V
(Compared with Therefore, the comparator 37 does not output the detected signal S (dl) because of the presence of ■ ( ) + V (Since it exceeds Xl, the same figure (b
), the noise detection signal S (d) is output.

This detection signal S fd+ is also input to the monostable multi-by-break 38 . Monostable multi high break 38
If a trigger is received within a certain period of time, the output will continue to be sent out, so when multipath distortion occurs, the sixth
As shown in FIG.

〔Effect of the invention〕

According to the present invention, it is possible to detect only short-time sudden large-amplitude noise, such as multipath distortion, from a series of noises over a relatively long period of time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a receiver noise detection device as an embodiment of the present invention, FIGS. 2 and 3 are block diagrams of conventional noise detection devices, and FIG. 4 is a block diagram of the generation of multipath distortion. 5 is a block diagram of an FM receiver using the noise detection device of FIG. 1, and FIG. 6 is a signal waveform diagram of each part of the device of FIG. 1. 1...F, M tune, 3...Noise detection circuit, 31
...High-pass filter, 32...Variable gain amplifier, 32
...Detector, 34.36... Integrator, 35... Differential amplifier, 37... Comparator, 38... Monostable multi-high break. Patent distributor Fujitsu Ten Ltd. Patent application agent

Claims (1)

[Claims] 1. An extraction circuit that uses a filter to extract high-frequency noise components from the detection output of a receiver; a variable gain control amplifier circuit that amplifies the high-frequency noise components extracted by the extraction circuit; an integrating circuit that time-integrates and smoothes the amplified output of the circuit; a control circuit that compares the integrated output of the integrating circuit with a predetermined first reference value and controls the gain of the amplifying circuit according to the amount of difference; and a comparison of comparing the amplified output of the amplifier circuit with a second reference value that is slightly larger than the first reference value, and outputting a noise detection output when the amplified output exceeds the second reference value. A receiver noise detection device comprising a circuit.