JP2012244461A - Communication device, method of controlling the same, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication device capable of accurately detecting a noise component included in a demodulation signal without detecting a distortion component of a sound signal wrongly as the noise component.SOLUTION: A communication device has: a mixer unit 16 converting an intermediate-frequency reception signal including a sound signal into a low-frequency reception signal; a detection unit 17 detecting the reception signal converted by the mixer unit 16 to reproduce the sound signal; a sound output unit 19 outputting the sound signal supplied from the detection unit 17; a noise detector 20 performing square arithmetic operation to the reception signal converted by the mixer unit 16 to generate an information signal including information on an amplitude element of the reception signal and information on a noise component; and a squelch controller 21 controlling to permit the sound output unit 19 to output the sound signal or make the sound output unit 19 stop outputting the sound signal, based on the information signal generated by the noise detector 20.

Description

  The present invention relates to a communication device, a communication device control method, and a computer program, and more particularly, to a communication device having a function of detecting signal strength of received radio waves and noise component strength, a communication device control method, and a computer program.

  In order to detect the intensity of a noise component with respect to the signal intensity of a received radio wave, a communication device including an FM detection unit having a noise detection function is generally known.

  FIG. 6 is a block diagram of a general FM detector 100 of an FM radio in the related art. In FIG. 6, a BPF (band pass filter) 101 attenuates high and low frequency unnecessary components included in a reception signal (IF input) of an intermediate frequency. The local oscillator 102 generates a local oscillation signal having a predetermined frequency. The phase shifter 103 generates a phase-shifted local oscillation signal obtained by delaying the phase of the local oscillation signal generated by the local oscillator 102 by 90 degrees.

  The mixer circuit 104 mixes the reception signal input from the BPF 101 and the local oscillation signal input from the local oscillator 102 to generate an I signal obtained by converting the intermediate frequency to a lower frequency, and an LPF (low-pass filter) 106. To enter. The mixer circuit 105 mixes the reception signal input from the BPF 101 and the phase-shifted local oscillation signal input from the phase shifter 103, generates a Q signal converted to a lower frequency, and inputs the Q signal to the LPF 107.

  The I and Q signals from the mixer circuits 104 and 105 are composed of a difference frequency obtained by subtracting the local oscillation frequency from the intermediate frequency and an addition frequency obtained by adding the intermediate frequency and the local oscillation frequency. The LPFs 106 and 107 attenuate the high frequency addition frequency and input the I signal and the Q signal having the low frequency difference frequency to the arctangent detection circuit 108, respectively.

  The arc tangent detection circuit 108 calculates the phase ωt = 2πft of the received signal based on the I signal and the Q signal input from the LPFs 106 and 107, respectively. The differentiation circuit 109 differentiates the phase ωt input from the arc tangent detection circuit 108 and inputs the detection signal including the original audio signal to the LPF 110 and the HPF (high-pass filter) 111 with a frequency ω = 2πf. This detection signal includes a noise component in addition to the audio signal. The LPF 110 attenuates unnecessary high-frequency components included in the audio signal input from the differentiation circuit 109 and outputs the audio signal.

  The HPF 111 attenuates the low frequency audio signal from the audio signal and noise component input from the differentiation circuit 109, extracts the high frequency noise component, and inputs the high frequency noise component to the rectifier circuit 112. The rectifier circuit 112 rectifies the high-frequency noise component input from the HPF 111, converts it into a DC voltage, and outputs it. This DC voltage value is a noise amount indicating the magnitude of noise included in the demodulated audio signal. That is, in the FM detection unit 100 in FIG. 6, a frequency band higher than the frequency band of the audio signal is regarded as a noise component and separated from the audio signal demodulated by the HPF 111. When the amount of noise is large, the audio output is stopped by the squelch function.

FIG. 7 is a diagram showing a constellation of a demodulated signal (symbol) in an ideal FM signal. In the constellation, a signal having the same phase is shown on the real axis (I axis) on the complex plane, and a signal having a phase shift of 90 degrees is shown on the imaginary axis (Q axis) on the complex plane. As shown in FIG. 7, in the case of an ideal FM signal, if the constellation is a unit circle, for example, a radius A and a phase φ (= ωt), a circle of y = Ae ^jωt is drawn. The differential of the phase (ωt) of the unit circle is the frequency (ω = 2πf), which is a detection signal.

  However, in practice, the constellation does not draw a unit circle as shown in FIG. 7 due to noise included in the FM signal, and has a distorted shape. FIG. 8 is a diagram showing a constellation of an FM signal containing a lot of noise. In FIG. 8, when the constellation crosses from point a to point b at a position far from the zero point (origin), the amount of phase change per unit time (φb−φa) is small. However, when crossing from the c point near the zero point to the d point, the amount of phase change (φd−φc) per unit time becomes large. Such noise with a large amount of phase change per unit time is pulse noise. FIG. 9 is a diagram illustrating a demodulated waveform when pulse noise occurs. When the constellation crosses the vicinity of the zero point, pulse noise indicated by a circle is generated.

  Generally, in a communication device that receives an audio signal, when a noise component is large, as described above, a squelch function that blocks output of an audio signal from a speaker or other audio output unit works.

  The following Patent Document 1 and Patent Document 2 disclose techniques for stopping audio output by a squelch function. For this reason, it is important to accurately detect the noise component included in the demodulated signal in order for the squelch function to work properly.

JP 2002-64388 A JP 2010-263315 A

  In the conventional general FM detector shown in FIG. 6, a frequency component higher than the frequency band of the audio signal is regarded as a noise component. However, due to the nature of the FM signal, the distortion component of the audio signal is also included in the frequency band of the audio signal, so that the distortion component becomes large when receiving an FM signal having a large frequency transition. Further, when transmitting a modulation waveform of an FM signal having a frequency band that theoretically extends infinitely, a necessary frequency band (for example, 12.5 kHz in the case of an analog signal, 95% to 99% of the total power) Only the original signal is transmitted, so the original signal cannot be completely demodulated. For this reason, even if the frequency transition is not large, a shortage portion of several% that is not demodulated is included in the received signal as a distortion component. As a result, there is a problem that the distortion component is erroneously detected as a noise component, and the audio signal is blocked by the squelch operation.

  Furthermore, since the value of the pulse noise changes abruptly only at that moment, the average value is not very stable even if the values are averaged. Accordingly, when ON / OFF of the squelch operation is controlled with a certain threshold value, the squelch control becomes unstable because it exceeds or falls below the threshold value. Of course, there is a method of providing hysteresis to the threshold, lowering the threshold once opened (allowing the output) and increasing the threshold once closed (stopping the output), or not closing several tens of milliseconds once opened Measures can also be taken. However, it is necessary to make various adjustments in consideration of the magnitude of the pulse noise, the frequency of occurrence, and the like, and considerably troublesome control is required. If a stable average value is to be obtained even if pulse noise occurs, it is necessary to calculate an average value for a sufficiently long time, which greatly affects the reaction speed of squelch control. . As described above, the conventional technique has a problem that the accuracy of the squelch control is lowered by the pulse noise included in the demodulated signal.

  The present invention has been made in view of the above circumstances, accurately detects a noise component included in a demodulated signal, does not erroneously detect a distortion component of an audio signal as a noise component, and is included in the demodulated signal. It is an object of the present invention to provide a communication device, a communication device control method, and a computer program that can prevent the accuracy of squelch control from being reduced by pulse noise generated.

A communication device according to a first aspect of the present invention is:
A signal conversion means for converting an intermediate frequency reception signal including an audio signal into a low frequency reception signal;
Signal detection means for detecting a reception signal converted by the signal conversion means and reproducing an audio signal;
Signal output means for outputting the audio signal reproduced by the signal detection means;
Information generating means for performing a squaring operation on the received signal converted by the signal converting means to generate an information signal including information on amplitude elements and noise components of the received signal;
Output control means for controlling permission or stop of output of an audio signal to the signal output means based on the information signal generated by the information generation means.

Preferably, the signal converting means converts the intermediate frequency received signal including the audio signal into a low frequency in-phase component and quadrature component received signal including the audio signals orthogonal to each other,
The information generation means includes a first multiplication means for generating a first information signal by performing a square operation on the in-phase component converted by the signal conversion means, and an orthogonal component converted by the signal conversion means. A second multiplying means for generating a second information signal by performing a square operation on the first and second information signals generated by the first and second multiplying means and combining them Signal synthesis means for generating an information signal, and noise extraction means for extracting a noise component of the synthesized information signal synthesized by the signal synthesis means,
The output control means controls permission or stop of output of an audio signal to the signal output means based on the noise component extracted by the noise extraction means,
It is characterized by that.

Preferably, the information generation unit extracts the amplitude component of the synthesized information signal synthesized by the signal synthesis unit, and the noise component extracted by the noise extraction unit is extracted by the amplitude extraction unit. Normalizing means for normalizing by the amplitude element,
The output control means controls permission or stop of output of an audio signal to the signal output means based on the noise component normalized by the normalization means.
It is characterized by that.

According to a second aspect of the present invention, a communication device control method comprises:
A signal conversion step of converting an intermediate frequency reception signal including an audio signal into a low frequency reception signal;
A signal detection step of detecting a reception signal converted by the signal conversion step and reproducing an audio signal;
A signal output step of outputting the audio signal reproduced by the signal detection step;
An information generation step of performing a square operation on the reception signal converted by the signal conversion step to generate an information signal including information on amplitude elements and noise components of the reception signal;
An output control step of controlling permission or stop of output of an audio signal with respect to the signal output step based on the information signal generated by the information generation step,
It is characterized by that.

Preferably, the signal conversion step converts the intermediate frequency reception signal including the audio signal into a low frequency in-phase component and a quadrature component reception signal including the audio signal orthogonal to each other,
The information generation step includes a first multiplication step for generating a first information signal by performing a square operation on the in-phase component converted by the signal conversion step, and an orthogonal component converted by the signal conversion step. A second multiplication step for generating a second information signal by performing a square operation on the first and second information signals generated by the first and second multiplication steps, and combining them A signal synthesis step for generating an information signal, and a noise extraction step for extracting a noise component of the synthesized information signal synthesized by the signal synthesis step,
The output control step controls permission or stop of output of an audio signal with respect to the signal output step based on the noise component extracted by the noise extraction step.
It is characterized by that.

Preferably, in the information generation step, an amplitude extraction step of extracting an amplitude element of the synthesized information signal synthesized by the signal synthesis step, and a noise component extracted by the noise extraction step are extracted by the amplitude extraction step. A normalization step of normalizing by an amplitude element,
The output control step controls permission or stop of the output of the audio signal with respect to the signal output step based on the noise component normalized by the normalization step.
It is characterized by that.

A computer program according to the third aspect of the present invention provides:
A computer having a function of processing a received signal;
A signal conversion means for converting an intermediate frequency reception signal including an audio signal into a low frequency reception signal;
Signal detection means for detecting a received signal converted by the signal conversion means and reproducing an audio signal;
Signal output means for outputting the audio signal reproduced by the signal detection means;
Information generating means for performing a squaring operation on the received signal converted by the signal converting means to generate an information signal including information on amplitude elements and noise components of the received signal;
Based on the information signal generated by the information generation means, the signal output means functions as an output control means for controlling permission or stop of output of an audio signal,
It is characterized by that.

  According to the communication device, the communication device control method, and the computer program of the present invention, the noise component included in the demodulated signal is accurately detected, the distortion component of the audio signal is not erroneously detected as the noise component, and the demodulation is performed. It is possible to prevent the accuracy of the squelch control from being lowered by the pulse noise included in the signal.

It is a schematic block diagram of the FM receiver in embodiment of the communication apparatus of this invention. FIG. 2 is a detailed block diagram of a detection unit and the like in FIG. 1. It is a figure which shows the relationship between the constellation which is a vector space by which FM signal containing much noise is mapped, and noise amount. It is a figure which shows the constellation of the demodulated signal in the ideal FM signal when a signal strength is large and when a signal strength is small. It is the figure which compared the relationship between the signal strength and noise amount in related technology and embodiment of this invention. It is a block diagram of the general FM detection part of the FM radio in related technology. It is a figure which shows the constellation of the demodulated signal in an ideal FM signal. It is a figure which shows the constellation of FM signal in which much noise is contained. It is a figure which shows the demodulation waveform when pulse noise generate | occur | produces.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. In addition, overlapping explanation is omitted.

(Embodiment)
FIG. 1 is a schematic block diagram of an FM receiver 10 in an embodiment of a communication device of the present invention. As shown in FIG. 1, the FM receiver 10 includes a reception antenna 11, a BPF (bandpass filter) 12, an RF amplifier 13, a mixer unit 14, an IF amplifier 15, a mixer unit 16, a detection unit 17, a BPF 18, and an audio output unit. 19, a noise detection unit 20, and a squelch control unit 21.

  The receiving antenna 11 receives RF (radio frequency) signals of a plurality of channels of FM radio waves and inputs them to a tuning circuit (not shown). The tuning circuit selectively tunes the high-frequency signal of the channel (frequency) according to the user's designation and inputs it to the BPF 12.

  The BPF 12 attenuates unnecessary frequency components from the RF signal input from the tuning circuit and inputs the attenuated frequency component to the RF amplifier 13.

  The RF amplifier 13 amplifies the RF signal input from the BPF 12 and inputs it to the mixer unit 14.

  The mixer unit 14 mixes an RF signal input from the RF amplifier 13 and a local oscillation signal having a predetermined frequency output from a local oscillator (not shown), converts the mixed signal into an IF (intermediate frequency) signal, and outputs IF Input to the amplifier 15.

  The IF amplifier 15 amplifies the IF signal input from the mixer unit 14 and inputs the amplified IF signal to the mixer unit 16.

  The mixer unit 16 includes an IF signal input from the IF amplifier 15, a local oscillation signal having a predetermined frequency output from a local oscillator (not shown), and a local part obtained by delaying the phase of the local oscillation signal by 90 degrees by a phase shifter. The oscillation signal is mixed and converted into an I signal that is a low-frequency in-phase component orthogonal to each other and a Q signal that is an orthogonal component, and these are input to the detection unit 17 and the noise detection unit 20.

  The detection unit 17 detects an audio signal based on the I signal and the Q signal input from the mixer unit 16 and inputs the detected audio signal to the BPF 18.

  The BPF 18 attenuates unnecessary frequency components (frequency components other than about 300 to 3000 Hz) included in the audio signal input from the detection unit 17 and inputs the attenuated frequency components to the audio output unit 19.

  The noise detection unit 20 inputs a noise component detected by performing multiplication processing, filtering processing, and rectification processing on the low frequency signal input from the mixer unit 16 to the squelch control unit 21.

  The squelch control unit 21 generates a control signal based on the noise component input from the noise detection unit 20 and inputs the control signal to the audio output unit 19.

  The audio output unit 19 includes a low-frequency amplifier and a speaker (not shown), performs an amplification process on the audio signal input from the BPF 18, and amplifies the audio signal according to the control signal input from the squelch control unit 21. The sound corresponding to the sound signal is output or the output is stopped.

  Next, detailed configurations and operations of the mixer unit 16, the detection unit 17, and the noise detection unit 20 will be described. FIG. 2 is a block diagram illustrating detailed configurations of the mixer unit 16, the detection unit 17, and the noise detection unit 20 of FIG. First, each component and each function in the mixer unit 16, the detection unit 17, and the noise detection unit 20 in FIG. 2 will be described.

  The mixer unit 16 includes a BPF 31, two mixer circuits 32 and 33, a local oscillator 34, a phase shifter 35, and LPFs 36 and 37.

  The BPF 31 attenuates unnecessary high frequency components and low frequency components included in the IF signal input from the IF amplifier 15 illustrated in FIG. 1 and inputs the attenuated high frequency components to the mixer circuits 32 and 33.

  The local oscillator 34 generates a local oscillation signal having a predetermined frequency and inputs it to the mixer circuit 32 and the phase shifter 35.

  The phase shifter 35 delays the phase of the local oscillation signal input from the local oscillator 34 by 90 degrees and inputs the delayed signal to the mixer circuit 33.

  The mixer circuit 32 converts the frequency of the IF signal input from the BPF 31 into a low frequency by the local oscillation signal input from the local oscillator 34. The mixer circuit 33 converts the frequency of the IF signal input from the BPF 31 to a low frequency by the local oscillation signal having a 90-degree phase delay input from the phase shifter 35.

  In the frequency conversion processing of the mixer circuits 32 and 33, the signal is converted into a low frequency signal having a difference frequency obtained by subtracting the local oscillation frequency from the intermediate frequency. In the frequency conversion processing, the high frequency obtained by adding the intermediate frequency and the local oscillation frequency. Components (this is called “image components”) are generated. For this reason, LPFs 36 and 37 are connected to the mixer circuits 32 and 33, respectively.

  The LPF 36 attenuates an image component generated in the mixer circuit 32 and inputs a low frequency signal to the detection unit 17 and the noise detection unit 20. Similarly, the LPF 37 attenuates an image component generated in the mixer circuit 33 and inputs a low frequency signal to the detection unit 17 and the noise detection unit 20.

  The low frequency signal converted by the mixer circuit 32 and filtered by the LPF 36 and the low frequency signal converted by the mixer circuit 33 and filtered by the LPF 37 have orthogonal phases. Therefore, as described above, generally, the low-frequency signal converted by the mixer circuit 32 is called an I signal (In-phase signal), and the low-frequency signal converted by the mixer circuit 33 is called a Q signal (Quadrate signal). ; Orthogonal component).

  The detection unit 17 includes an arc tangent detection circuit 38, a differentiation circuit 39, and an LPF 40.

  The arc tangent detection circuit 38 performs an arc tangent calculation process for calculating an arc tangent value with respect to a ratio of the I signal and the Q signal input from the LPFs 36 and 37 to one input end and the other input end, respectively. And input to the differentiation circuit 39. Details of the arctangent calculation processing will be described later.

  The differentiation circuit 39 calculates the frequency by differentiating the arc tangent value input from the arc tangent detection circuit 38 with respect to time, and inputs the audio signal reproduced based on the calculated frequency to the LPF 40.

  The LPF 40 attenuates unnecessary high frequency components contained in the audio signal input from the differentiating circuit 39 and inputs the attenuated frequency component to the audio output unit 19 of FIG.

  The noise detection unit 20 includes two square calculation circuits 41 and 42, a synthesis circuit 43, an HPF 44, a rectification circuit 45, an LPF 46, and a normalization circuit 47.

  The squaring operation circuit 41 performs a squaring operation on the I signal input from the LPF 36 to calculate an information signal including amplitude component information and noise component information of the I signal. Input to the input terminal. Similarly, the squaring operation circuit 42 performs a squaring operation on the Q signal input from the LPF 37 to calculate an information signal including information on the amplitude element and noise component of the Q signal and combining circuit 43. To the other input terminal.

  The combining circuit 43 combines the information signals of the I signal and the Q signal input from the square calculation circuits 41 and 42, respectively, and inputs the combined information signal to the HPF 44 and the LPF 46.

  The HPF 44 extracts a high-frequency noise component included in the combined information signal input from the combining circuit 43 and inputs it to the rectifier circuit 45.

  The rectifier circuit 45 rectifies the high frequency (alternating current) noise component input from the HPF 44, converts it to a DC voltage indicating the amount of noise, and inputs it to the normalizing circuit 47.

  The LPF 46 extracts the amplitude element included in the combined information signal input from the combining circuit 43 and inputs it to the normalization circuit 47.

  The normalization circuit 47 normalizes (for example, divides) the DC voltage value input from the rectifier circuit 45 by the amplitude element input from the LPF 46, and inputs it to the squelch control unit 21 in FIG. 1 as a noise output.

  Next, detailed operations of the detector 17 and the noise detector 20 will be described with reference to FIGS. FIG. 3 is a diagram showing the relationship between the constellation, which is a vector space in which the FM signal containing a lot of noise shown in FIG. 8 is mapped, and the amount of noise. FIG. 4 is a diagram showing a demodulated signal constellation in an ideal FM signal when the signal strength is high and when the signal strength is low.

When an ideal FM signal including no noise component from the receiving antenna 11, that is, the FM signal shown in FIG. 7 is input, the FM signal included in the IF signal input to the mixer circuits 32 and 33 is as follows. It is represented by the formula (1). In the following equation (1), ω = 2πf is the frequency of the FM signal, ω _c = 2πf _c is the center frequency of the FM signal, and Δω = 2πΔf is the frequency deviation of the FM signal. The frequency deviation Δω is information that bears the audio signal.

Since the I signal that is frequency-converted from the mixer circuit 32 and output from the LPF 36 is in phase with the FM signal included in the IF signal, it is expressed by the following equation (2). On the other hand, the Q signal that is frequency-converted from the mixer circuit 33 and output from the LPF 37 has a phase difference of 90 degrees with respect to the FM signal included in the IF signal, and is expressed by the following equation (3).

一般に、cosθ及びsinθとtanθとの関係は下記の式（７）で表される。

したがって、式（５）乃至（７）に基づいて下記の式（８）を導き出せる。

Actually, the FM signal input from the receiving antenna 11 includes a noise component. In other words, the “relative” noise component is included in the FM signal which is the “desired signal”. “Relative” means, for example, that if the signal strength of the received signal is large but the purity (desired signal / noise component) is low, the noise is considered to be large and the sound is cut off. Even if the intensity is small, if the purity is high, it is considered that the noise component is small, and the sound is output. The FM signal included in the IF signal input to the mixer circuits 32 and 33 is expressed by the following formula (4) as a synthesis of the “desired signal” and the “relative” noise component. Therefore, the in-phase component I signal output from the mixer circuit 32 and the quadrature component Q signal output from the mixer circuit 33 are expressed by the following equations (5) and (6), respectively.

In general, the relationship between cos θ and sin θ and tan θ is expressed by the following equation (7).

Therefore, the following equation (8) can be derived based on the equations (5) to (7).

The arc tangent detection circuit 38 performs the calculation of the following equation (9) based on the equation (8), and inputs the calculated value of (ω _c + Δω) t to the differentiation circuit 39.

The differentiation circuit 39 differentiates the value of (ω _c + Δω) t input from the arc tangent detection circuit 38 with time t according to the following equation (10) and calculates the value of (ω _c + Δω), that is, the FM signal. The audio signal represented by the center frequency ω _c and the frequency deviation Δω is input to the LPF 40.

The LPF 40 attenuates frequency components higher than the audio frequency band included in the signal (ω _c + Δω), and inputs an audio signal having a high signal-to-noise ratio (S / N) to the audio output unit in FIG.

すなわち、２乗演算回路４１は、振幅要素Ａ^２及びノイズ成分Ａ^２（２η（ｔ）＋η（ｔ）^２）を含む情報信号（これを「第１の情報信号」という）を合成回路４３に入力する。 The square calculation circuit 41 performs a square calculation on I (t), which is an I signal input from the LPF 36, and outputs a signal represented by the following expression (11) to one input terminal of the synthesis circuit 43. To enter.

That is, the square calculation circuit 41 sends an information signal (this is referred to as a “first information signal”) including the amplitude element A ² and the noise component A ² (2η (t) + η (t) ² ) to the synthesis circuit 43. input.

すなわち、２乗演算回路４２も、振幅要素Ａ^２及びノイズ成分Ａ^２（２η（ｔ）＋η（ｔ）^２）を含む情報信号（これを「第２の情報信号」という）を合成回路４３に入力する。 Similarly, the square calculation circuit 42 performs a square calculation on Q (t) that is a Q signal input from the LPF 37, and generates a signal represented by the following expression (12) as the other of the synthesis circuit 43. Input to the input terminal.

In other words, the square calculation circuit 42 also sends an information signal including the amplitude element A ² and the noise component A ² (2η (t) + η (t) ² ) (referred to as a “second information signal”) to the synthesis circuit 43. input.

The synthesis circuit 43 synthesizes the first information signal and the second information signal input from the square calculation circuit 41 and the square calculation circuit 42, and generates a combined information signal represented by the following equation (13). Input to HPF 44 and LPF 46.

HPF44 and the first term of the DC input above synthetic information signal LPF46 amplitude component A ² represents the square of the radius of a unit circle of a dotted line shown in FIG. On the other hand, the AC noise component A ² (2η (t) + η (t) ² ) of the second term of the combined information signal is a fluctuation amount of the deviation width D from the unit circle.

  The HPF 44 attenuates the direct current amplitude element of the first term of the combined information signal expressed by the equation (13), extracts the high frequency noise component of the second term, and inputs it to the rectifier circuit 45.

  The rectifier circuit 45 rectifies the high frequency noise component of the combined information signal input from the HPF 44 and inputs the converted DC voltage (referred to as “N”) to the normalization circuit 47. Therefore, the DC voltage N represents the amount of noise.

  The LPF 46 attenuates the high-frequency noise component of the second term of the combined information signal expressed by the equation (13), extracts the direct-current amplitude element of the first term, and inputs it to the normalization circuit 47.

When the DC voltage N obtained by rectifying the noise component extracted by the HPF 44 is input from the rectifier circuit 45, the normalization circuit 47 normalizes the DC voltage N by the amplitude element extracted by the LPF 46. For example, the normalization circuit 47 divides the DC voltage N amplitude component A ^2. By this normalization, it is possible to avoid the dependence of the noise component on the signal intensity.

As shown in FIG. 4, since the fluctuation amount, that is, the noise component from the two unit circles having different radii A1 and A2 depends on the respective radius, that is, the signal intensity, the DC voltage representing each noise amount is represented by N1 and N2. Then, it normalizes by the calculation of N1 / A1 ² and N2 / A2 ² . Assuming that the normalized DC voltage is Nr, the normalization circuit 47 inputs the normalized DC voltage Nr to the squelch control unit 21 shown in FIG.

  As a result, the squelch control unit 21 controls the audio output unit 19 shown in FIG. 1 based on the DC voltage Nr input from the normalization circuit 47 as described above.

  When the signal strength is stable within a predetermined range, a noise component is extracted by the HPF 44, and the DC voltage N rectified by the rectifier circuit 45 is not normalized, and the squelch control unit 21 shown in FIG. It may be configured to input to

  Furthermore, as a modification of the embodiment, a configuration further including an amplitude detection circuit that detects whether or not the signal intensity is in a predetermined range is possible. According to this configuration, when the signal strength is within a predetermined range, the DC voltage N is input to the squelch control unit 21 without normalization, and when the signal strength is outside the predetermined range, the normalized DC voltage Nr is input. Is input to the squelch control unit 21.

  As described above, the communication device according to the embodiment includes the mixer unit 16 (signal conversion unit) that converts an intermediate frequency reception signal including an audio signal into a low frequency reception signal, and the reception signal converted by the mixer unit 16. Is detected, and a sound signal is reproduced by a detection unit 17 (signal detection unit), a sound output unit 19 (signal output unit) that outputs a sound signal reproduced by the detection unit 17, and a reception converted by the mixer unit 16 A noise detection unit 20 (information generation unit) that performs a square operation on the signal to generate an information signal including information on amplitude components and noise components of the received signal, and information generated by the noise detection unit 20 A squelch control unit 21 (output control means) that controls permission or stop of the output of the audio signal to the audio output unit 19 based on the signal.

  Therefore, according to the communication device of the embodiment, the noise component included in the demodulated signal is accurately detected, and the distortion component of the audio signal is not erroneously detected as the noise component. As a result, it is possible to avoid squelch blocking due to a demodulated signal erroneously detected as a noise component. Further, there are an advantage that a noise fluctuation section is long and a noise component can be extracted stably.

  In the communication device of the embodiment, the mixer unit 16 converts the intermediate frequency received signal including the audio signal into an I signal that is a low-frequency in-phase component orthogonal to each other and a Q signal that is an orthogonal component. The noise detecting unit 20 performs a square operation on the in-phase component converted by the mixer unit 16 to generate a first information signal, and a mixer unit 16 generates a first information signal. Generated by a square operation circuit 42 (second multiplication means) that performs a square operation on the converted orthogonal component to generate a second information signal, a square operation circuit 41, and a square operation circuit 42. A combining circuit 43 (signal combining unit) that combines the first and second information signals to generate a combined information signal; and an HPF 44 (noise extraction unit) that extracts a noise component of the combined information signal combined by the combining circuit 43. And). The squelch control unit 21 controls the audio output unit 19 to permit or stop the output of the audio signal based on the noise component extracted by the HPF 44.

  Therefore, the noise component included in the demodulated signal is accurately detected, the distortion component of the audio signal is not erroneously detected as a noise component, and the accuracy of the squelch control is reduced due to the pulse noise included in the demodulated signal. Can be prevented.

  Further, in the communication device according to the embodiment, the noise detection unit 20 extracts, by the LPF 46, an LPF 46 (amplitude extraction unit) that extracts the amplitude element of the combined information signal combined by the combining circuit 43 and the noise component extracted by the HPF 44. And a normalizing circuit 47 (normalizing means) for normalizing with the amplitude element. The squelch control unit 21 controls the audio output unit 19 to permit or stop the output of the audio signal based on the noise component normalized by the normalization circuit 47.

  Therefore, by avoiding the dependence of the noise component on the signal intensity, the noise component can be reliably detected even when the signal intensity is high. FIG. 5 is a diagram comparing the relationship between the signal strength and the amount of noise in the related art and the embodiment of the present invention. In FIG. 5, the relationship between the signal intensity and the noise amount in the related art is indicated by a dotted line, and the relationship between the signal intensity and the noise amount in the embodiment of the present invention is indicated by a solid line. As shown in FIG. 5, the signal strength sig2 of the present invention is larger than the signal strength sig1 of the related art as the maximum signal strength for detecting a noise amount equal to or greater than a predetermined threshold TH. Thus, according to the embodiment of the present invention, it is possible to reliably detect a noise component even when the signal intensity is high.

  In the above embodiment, the communication device is configured by the hardware shown in FIGS. 1 and 2, but the configuration of the present invention is not limited to hardware. A part of the communication device, for example, the noise detection unit 20 may be configured by a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. According to this configuration, the CPU can read a program stored in advance in the ROM into the RAM, control the communication device, and execute signal processing similar to that in the above embodiment. Thus, the invention of the communication device control method is realized.

  Further, the CPU reads a program read from a computer-readable recording medium or a program downloaded via a communication line such as the Internet into the RAM, controls the communication device, and controls the hardware shown in FIGS. The function can be executed by a computer. Thereby, the invention of the computer program is realized.

  The above embodiments are merely examples for explaining the present invention. Without departing from the spirit and scope of the present invention, other embodiments and various modifications that can be easily conceived by those skilled in the art based on the above-described embodiments also belong to the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 FM receiver 11 Reception antenna 12, 18, 31 Band pass filter 13 RF amplifier 14, 16 Mixer part 15 IF amplifier 17 Detection part 19 Audio | voice output part 20 Noise detection part 21 Squelch control part 32, 33 Mixer circuit 34 Local oscillator 35 Phase shifter 36, 37, 40, 46 Low-pass filter 38 Arc tangent detection circuit 39 Differentiation circuit 41, 42 Square calculation circuit 43 Synthesis circuit 44 High-pass filter 45 Rectification circuit 47 Normalization circuit

Claims (7)

A signal conversion means for converting an intermediate frequency reception signal including an audio signal into a low frequency reception signal;
Signal detection means for detecting a reception signal converted by the signal conversion means and reproducing an audio signal;
Signal output means for outputting the audio signal reproduced by the signal detection means;
Information generating means for performing a squaring operation on the received signal converted by the signal converting means to generate an information signal including information on amplitude elements and noise components of the received signal;
An output control means for controlling permission or stop of output of an audio signal to the signal output means based on the information signal generated by the information generation means. The signal conversion means converts an intermediate frequency reception signal including an audio signal into a low frequency in-phase component and an orthogonal component reception signal including audio signals orthogonal to each other,
The information generation means includes a first multiplication means for generating a first information signal by performing a square operation on the in-phase component converted by the signal conversion means, and an orthogonal component converted by the signal conversion means. A second multiplying means for generating a second information signal by performing a square operation on the first and second information signals generated by the first and second multiplying means and combining them Signal synthesis means for generating an information signal, and noise extraction means for extracting a noise component of the synthesized information signal synthesized by the signal synthesis means,
The output control means controls permission or stop of output of an audio signal to the signal output means based on the noise component extracted by the noise extraction means,
The communication device according to claim 1. The information generating means includes an amplitude extracting means for extracting an amplitude element of the combined information signal synthesized by the signal synthesizing means, and a noise component extracted by the noise extracting means by the amplitude element extracted by the amplitude extracting means. Normalization means for normalizing, and
The output control means controls permission or stop of output of an audio signal to the signal output means based on the noise component normalized by the normalization means.
The communication device according to claim 2. A signal conversion step of converting an intermediate frequency reception signal including an audio signal into a low frequency reception signal;
A signal detection step of detecting a reception signal converted by the signal conversion step and reproducing an audio signal;
A signal output step of outputting the audio signal reproduced by the signal detection step;
An information generation step of performing a square operation on the reception signal converted by the signal conversion step to generate an information signal including information on amplitude elements and noise components of the reception signal;
An output control step of controlling permission or stop of output of an audio signal with respect to the signal output step based on the information signal generated by the information generation step,
A control method for a communication device. By the signal conversion step, the reception signal of the intermediate frequency including the audio signal is converted into the reception signal of the low-frequency in-phase component and the orthogonal component including the audio signal orthogonal to each other,
The information generation step includes a first multiplication step for generating a first information signal by performing a square operation on the in-phase component converted by the signal conversion step, and an orthogonal component converted by the signal conversion step. A second multiplication step for generating a second information signal by performing a square operation on the first and second information signals generated by the first and second multiplication steps, and combining them A signal synthesis step for generating an information signal, and a noise extraction step for extracting a noise component of the synthesized information signal synthesized by the signal synthesis step,
The output control step controls permission or stop of output of an audio signal with respect to the signal output step based on the noise component extracted by the noise extraction step.
The method of controlling a communication device according to claim 4. The information generation step includes an amplitude extraction step for extracting an amplitude element of the combined information signal combined by the signal combining step, and a noise component extracted by the noise extraction step by the amplitude element extracted by the amplitude extraction step. A normalizing step for normalizing, and
The output control step controls permission or stop of the output of the audio signal with respect to the signal output step based on the noise component normalized by the normalization step.
The communication apparatus control method according to claim 5, wherein: A computer having a function of processing a received signal;
A signal conversion means for converting an intermediate frequency reception signal including an audio signal into a low frequency reception signal;
Signal detection means for detecting a received signal converted by the signal conversion means and reproducing an audio signal;
Signal output means for outputting the audio signal reproduced by the signal detection means;
Information generating means for performing a squaring operation on the received signal converted by the signal converting means to generate an information signal including information on amplitude elements and noise components of the received signal;
Based on the information signal generated by the information generation means, the signal output means functions as an output control means for controlling permission or stop of output of an audio signal,
A computer program characterized by the above.

Images