JP5109780B2 - Tone signal detection apparatus, tone signal detection method, and program - Google Patents

Description

  The present invention relates to a tone signal detection apparatus, a tone signal detection method suitable for preventing erroneous detection of a tone signal due to noise, and a program for realizing these on a computer.

  When communicating using an FM (Frequency Modulation) method or the like, a technique using a tone signal is known as a technique for determining whether or not a call is established between a transmitter and a receiver. Specifically, the transmitter superimposes and transmits a continuous single-frequency tone signal in advance to the modulated signal, and the receiver extracts the frequency component of the tone signal from the demodulated signal using a bandpass filter, It is determined whether or not the call is established based on whether or not the frequency component exceeds a predetermined value. When the receiver determines that the call is not established, the receiver prevents noise from being output from the speaker by turning off the relay prepared on the path from the demodulator to the speaker.

  Here, when noise having a frequency component of the same frequency as the tone signal is superimposed on the demodulated signal, the receiver may erroneously detect the noise as the tone signal. As a technique for solving such a problem, for example, Patent Document 1 discloses a technique for extracting a frequency component of a tone signal frequency (hereinafter referred to as “tone frequency”) and extracting a frequency component near the tone frequency. A tone signal detection circuit for preventing erroneous detection of a tone signal by using a first filter, a second filter that attenuates the frequency component of the tone frequency and extracts a frequency component near the tone frequency, and a subtractor is disclosed. Yes.

Specifically, the first filter outputs the frequency component due to the tone signal and the frequency component due to noise, and the second filter outputs only the frequency component due to noise. The subtracter obtains and outputs only the frequency component based on the tone signal by subtracting the frequency component output from the second filter from the frequency component output from the first filter.
Japanese Patent Laid-Open No. 11-163748

  Here, there is a strong desire to prevent erroneous detection of a tone signal by switching the configuration or reference for detecting the tone signal according to the situation. The tone signal detection circuit disclosed in Patent Document 1 is not a configuration for detecting a tone signal, a reference, or the like according to a situation.

  The present invention has been made in view of the above problems, and provides a tone signal detection apparatus, a tone signal detection method suitable for preventing erroneous detection of a tone signal due to noise, and a program for realizing these on a computer. The purpose is to do.

To achieve the above object, a tone signal detection apparatus according to the first aspect of the present invention provides:
A tone signal detection device for detecting a tone signal of a predetermined frequency included in an input signal,
A first filter having a gain peak at a frequency higher and lower than the frequency of the tone signal ;
Have a different gain characteristic to the first filter, a second filter having a frequency substantially gain peak of the same frequency of the tone signal,
Extraction means for extracting a frequency component of a frequency corresponding to the tone signal from the supplied signal;
It is determined whether the signal intensity of the signal extracted by the extraction means exceeds a predetermined value, and when it is determined that the signal intensity of the signal does not exceed the predetermined value, a non-detection signal is output, Discriminating means for outputting a detection signal when it is determined that the signal intensity of the signal exceeds a predetermined value;
A signal obtained by applying an input signal to the first filter is supplied to the extraction unit while the non-detection signal is output by the determination unit, and an input is performed while the detection signal is output by the determination unit. Supply means for supplying a signal obtained by applying a signal to the second filter to the extraction means;
It is characterized by that.

  The first filter includes a first band pass filter having a gain peak at a frequency higher than the frequency of the tone signal and a second band pass filter having a gain peak at a frequency lower than the frequency of the tone signal. It can comprise from the combination.

  The extraction means includes normalization means for normalizing the signal level of the supplied signal, normalizes the supplied signal by the normalization means, and corresponds to the frequency of the tone signal from the normalized signal. It is desirable to extract frequency components.

  The normalization unit may normalize the signal level of the supplied signal by binarizing using a predetermined threshold value.

  The normalizing means may determine a reference value indicating the intensity of the signal based on the signal level of the supplied signal, and normalize the signal by dividing the signal level of the supplied signal by the reference value. .

  The supplying means further comprises delay means for making the delay time of the signal that has passed through the first filter substantially the same as the delay time of the signal that has passed through the second filter. Is desirable.

To achieve the above object, a tone signal detection method according to a second aspect of the present invention includes:
A tone signal detection method for detecting a tone signal having a predetermined frequency included in an input signal, wherein the tone signal detection method has a first gain peak at a frequency higher and lower than the frequency of the tone signal . and a filter, said to have a different gain characteristic to the first filter, a second filter having a frequency substantially gain peak of the same frequency of the tone signal, extraction means, and determination means, supplied And a tone signal detection apparatus comprising: means for detecting a tone signal;
The extraction means extracts a frequency component of a frequency corresponding to the tone signal from the supplied signal;
Non-detection when the determination means determines whether the signal intensity of the signal extracted by the extraction means exceeds a predetermined value, and determines that the signal intensity of the signal does not exceed the predetermined value When a signal is output and it is determined that the signal strength of the signal exceeds a predetermined value, a detection signal is output,
While the non-detection signal is output by the determination unit, the supply unit supplies a signal obtained by applying an input signal to the first filter to the extraction unit, and the detection signal is output by the determination unit. A signal obtained by applying an input signal to the second filter while the signal is supplied to the extraction means.
It is characterized by that.

In order to achieve the above object, a program according to the third aspect of the present invention provides:
Computer
A program for functioning as a tone signal detection device for detecting a tone signal of a predetermined frequency included in an input signal,
The program runs the computer
A first filter having a gain peak at a frequency higher and lower than the frequency of the tone signal ;
The have a different gain characteristic to the first filter, a second filter having a frequency substantially gain peak of the same frequency of the tone signal,
Extraction means for extracting a frequency component of a frequency corresponding to the tone signal from the supplied signal;
It is determined whether the signal intensity of the signal extracted by the extraction means exceeds a predetermined value, and when it is determined that the signal intensity of the signal does not exceed the predetermined value, a non-detection signal is output, Discrimination means for outputting a detection signal when it is determined that the signal intensity of the signal exceeds a predetermined value;
A signal obtained by applying an input signal to the first filter is supplied to the extraction unit while the non-detection signal is output by the determination unit, and an input is performed while the detection signal is output by the determination unit. Supply means for supplying a signal obtained by applying a signal to the second filter to the extraction means;
It is made to function as.

  According to the tone signal detection apparatus, tone signal detection method, and program according to the present invention, it is possible to reduce false detection of a tone signal due to noise.

  Hereinafter, a tone signal detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  First, a reception apparatus including a tone signal detection apparatus according to an embodiment of the present invention will be briefly described with reference to FIG.

  As shown in FIG. 1, the receiving apparatus 1000 includes an antenna 10, a high frequency amplification unit 20, a frequency mixing unit 30, a local oscillator 40, an intermediate frequency amplification unit 50, a demodulation unit 60, an audio signal removal LPF ( A low pass filter (65), a low frequency amplification unit (70), an audio reproduction switch (80), a tone signal removal HPF (High Pass Filter) 81, a power amplification unit (82), a speaker (90), and a tone signal detection device (100). Prepare.

  The antenna 10 takes in a carrier wave (hereinafter referred to as “received signal”) on which a signal including a tone signal is placed.

  The high frequency amplifying unit 20 amplifies the reception signal received from the antenna 10. The high-frequency amplifier 20 is configured using, for example, a high-electron mobility transistor with low noise characteristics.

  The frequency mixing unit 30 mixes the reception signal supplied from the high-frequency amplification unit 20 and the local oscillation signal supplied from the local oscillator 40, so that the frequency-shifted reception signal (hereinafter referred to as “intermediate frequency signal”) is obtained. ).

  The local oscillator 40 generates a local oscillation signal. The frequency of the local oscillation signal is a frequency obtained by subtracting the frequency of the intermediate frequency signal from the frequency of the reception signal, or a frequency obtained by adding the frequency of the intermediate frequency signal to the frequency of the reception signal. The local oscillator 40 is composed of a known oscillation circuit including a crystal oscillator, for example.

  The intermediate frequency amplification unit 50 amplifies the intermediate frequency signal supplied from the frequency mixing unit 30.

  The demodulator 60 demodulates the intermediate frequency signal supplied from the intermediate frequency amplifier 50 to generate a demodulated signal including a tone signal (hereinafter referred to as “demodulated signal”). The demodulator 60 includes a known demodulator circuit and the like.

  The audio signal removal LPF 65 passes a frequency component lower than a predetermined frequency among the frequency components of the demodulated signal supplied from the demodulator 60 and attenuates a frequency component higher than the predetermined frequency. In order for the tone signal detection apparatus 100 to detect a tone signal, only a frequency component (frequency component of a relatively low frequency) within a frequency range that can be taken as a tone signal is necessary. In other words, the frequency component of the voice band (frequency component of a relatively high frequency) is not necessary.

  However, the demodulated signal supplied from the demodulator 60 includes a relatively high frequency component constituting the audio signal in addition to a relatively low frequency component constituting the tone signal. If the frequency component of the audio band is left, there is a possibility that the frequency component of the audio band is turned back at a frequency half that of the sampling frequency described later and mixed into the frequency band of the tone signal. In addition, the intensity of the audio signal is considerably stronger than the intensity of the tone signal. For this reason, the audio signal removal LPF 65 sufficiently attenuates the frequency component of the audio band among the frequency components of the demodulated signal, and then supplies the demodulated signal to the tone signal detection device 100.

  The low frequency amplifier 70 amplifies the demodulated signal supplied from the demodulator 60. The low frequency amplifying unit 70 includes, for example, a known class A amplifier circuit or class B push-pull amplifier circuit.

  The audio reproduction switch 80 supplies the demodulated signal supplied from the low frequency amplification unit 70 to the speaker 90 in accordance with the control signal supplied from the tone signal detection device 100. The audio reproduction switch 80 supplies the demodulated signal supplied from the low-frequency amplifier 70 to the speaker 90 while the detection signal indicating that the tone signal is detected from the tone signal detection device 100 ( Open squelch.) On the other hand, the sound reproduction switch 80 is supplied to the speaker 90 of the demodulated signal supplied from the low-frequency amplifier 70 while the non-detection signal indicating that the tone signal is not detected is supplied from the tone signal detection device 100. Shut off the supply (close the squelch).

  The tone signal removal HPF 81 passes a frequency component higher than a predetermined frequency among the frequency components of the demodulated signal supplied from the audio reproduction switch 80 and attenuates a frequency component lower than the predetermined frequency. That is, the tone signal removal HPF 81 attenuates the frequency component of the relatively low frequency constituting the tone signal among the frequency components of the demodulated signal, and the power amplifying unit 82 only the frequency component of the relatively high frequency constituting the audio signal. To supply.

  The power amplifier 82 amplifies the demodulated signal supplied from the tone signal removal HPF 81 and supplies the amplified signal to the speaker 90. The power amplifying unit 82 includes, for example, a known class A amplifier circuit or class B push-pull amplifier circuit.

  The speaker 90 converts the demodulated signal supplied from the power amplifier 82 into audio data and reproduces it.

  The tone signal detection apparatus 100 detects a tone signal having a predetermined frequency included in the demodulated signal supplied from the audio signal removal LPF 65. The tone signal detection device 100 supplies the detection signal to the sound reproduction switch 80 while the tone signal is detected. On the other hand, the tone signal detection device 100 supplies a non-detection signal to the sound reproduction switch 80 while the tone signal is not detected. In the present embodiment, the demodulated signal supplied from the audio signal removal LPF 65 to the tone signal detection apparatus 100 is assumed to be a digital signal sampled at a predetermined sampling frequency fs (Hz).

  Next, the tone signal detection apparatus 100 will be described in detail with reference to FIG. The tone signal detection device 100 is a circuit that determines whether or not a tone signal having a predetermined frequency is included in the demodulated signal and outputs a detection signal or a non-detection signal. The tone signal detection apparatus 100 is configured using, for example, a computer system including a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).

  As shown in FIG. 2, the tone signal detection apparatus 100 includes a noise removal BPF (Band Pass Filter) 101, a frequency shift unit 102, a local oscillator 103, an image removal BPF 104, a non-detection BPF 105, and a non-detection. A delay unit 106, a detection time BPF 107, a detection time delay unit 108, a filter changeover switch 109, a normalization unit 110, a signal extraction BPF 111, a signal strength detection unit 112, and a control unit 113 are provided.

  The noise removal BPF 101 attenuates the frequency component of the frequency outside the range of frequencies (for example, 67 to 250 Hz) that can be taken as the frequency of the tone signal among the frequency components of the demodulated signal supplied from the audio signal removal LPF 65. That is, the noise removal BPF 101 removes a DC component and a high frequency component due to noise.

  The frequency shift unit 102 shifts and outputs the frequency of the signal supplied from the noise removal BPF 101 by mixing the signal supplied from the noise removal BPF 101 and the local oscillation signal supplied from the local oscillator 103. The frequency shift unit 102 shifts the frequency of the signal supplied from the noise removal BPF 101 so that the same frequency can be processed even if the frequency of the tone signal to be detected is changed. The frequency to be shifted is determined by the frequency of the local oscillation signal.

  The local oscillator 103 generates a local oscillation signal having a frequency shift amount of the signal supplied from the noise removal BPF 101 to the frequency shift unit 102 as a frequency. Here, the frequency of the tone signal included in the shifted signal is a tone frequency ftone (Hz). Hereinafter, a case will be described in which whether or not a tone signal is included is determined based on whether or not the frequency component of the tone frequency ftone in the signal has a predetermined signal intensity in the processing after the image removal BPF 104. Note that the tone frequency ftone is desirably set to a frequency that is not close to an image frequency fimag (Hz), which will be described later, for example, 300 Hz or more.

  For example, assuming that the frequency of the tone signal before shifting is the frequency before shifting fin (Hz) and the frequency of the local oscillation signal is the oscillating frequency fosc (Hz), each frequency is set so that fosc = ftone−fin. As a result, the frequency of the signal output from the frequency shift unit 102, that is, the tone frequency ftone is ftone = fin + fosc. The local oscillator 103 is composed of a frequency synthesizer such as a DDS (Direct Digital Synthesizer), a crystal oscillator, or the like.

  The image removal BPF 104 removes the frequency component of the image frequency fimag (fimag = fosc−fin) from the signal supplied from the frequency shift unit 102. When the demodulated signal output from the demodulator 60 includes a tone signal, the signal supplied from the frequency shift unit 102 includes the frequency component of the image frequency fimag in addition to the frequency component of the tone frequency ftone. As the image removal BPF 104, a band pass filter having a filter characteristic capable of removing the frequency component of the image frequency fimag is used.

  The non-detection BPF 105 extracts only a frequency component having a frequency close to the tone frequency ftone from the signal supplied from the image removal BPF 104. Here, the filter characteristics of the non-detecting BPF 105 will be described with reference to FIGS.

  The non-detection BPF 105 is shown as a filter (hereinafter referred to as “filter 1”) having a transmission characteristic (hereinafter referred to as “gain characteristic”) shown as the filter 1 in FIG. And a filter having a gain characteristic (hereinafter referred to as “filter 2”). In the following description, a case where the non-detection BPF 105 is configured by connecting the filter 1 and the filter 2 in series will be described. For comparison, the gain characteristic of the BPF 107 at the time of detection is shown as a filter 3 in FIG. As shown in FIG. 3, the filter 1 is a bandpass filter having a gain peak at a frequency higher than the tone frequency ftone, and the filter 2 is a bandpass filter having a gain peak at a frequency lower than the tone frequency ftone. It is.

  Here, as shown in FIG. 3, a case will be described in which the filter 1 and the filter 2 have the same gain at the tone frequency ftone. The gain of the filter 1 at the peak of the gain of the filter 1 is about 12 dB higher than the gain of the filter 1 at the tone frequency ftone. The gain of the filter 2 at the gain peak of the filter 1 is about 6 dB lower than the gain of the filter 2 at the tone frequency ftone. Here, since the non-detection BPF 105 is configured by connecting the filter 1 and the filter 2 in series, the gain of the non-detection BPF 105 at the peak of the gain of the filter 1 is the gain of the non-detection BPF 105 at the tone frequency ftone. About 6 dB (about 12 dB to about 6 dB).

  Similarly, the gain of the non-detecting BPF 105 at the gain peak of the filter 2 is also higher than the gain of the non-detecting BPF 105 at the tone frequency ftone. Thus, the non-detecting BPF 105 has gain peaks at frequencies higher and lower than the gain at the tone frequency ftone. FIG. 4A shows the gain characteristics of the non-detecting BPF 105, that is, the total gain characteristics of the two filters, the filter 1 and the filter 2.

  At the time of detection, the BPF 107 extracts only a frequency component having a frequency close to the tone frequency ftone from the signal supplied from the image removal BPF 104. FIG. 4B shows the gain characteristics of the BPF 107 at the time of detection. As shown in FIG. 4B, the detection BPF 107 is a band-pass filter having a gain peak at the tone frequency ftone.

  The non-detection delay unit 106 delays the signal supplied from the non-detection BPF 105 by a predetermined time and supplies the delayed signal to the filter selector switch 109. The detection delay unit 108 delays the signal supplied from the detection BPF 107 by a predetermined time and supplies the delayed signal to the filter changeover switch 109.

  The non-detection delay unit 106 and the detection delay unit 108 are the time until the signal output from the image removal BPF 104 is supplied to the filter changeover switch 109 via the non-detection BPF 105 and the non-detection delay unit 106. The signals output from the image removal BPF 104 are delayed so that the time until the signal is supplied to the filter changeover switch 109 via the detection BPF 107 and the detection delay unit 108 is the same. Let

  The non-detection delay unit 106 and the detection delay unit 108 can continuously perform tone signal detection processing even when the filter is switched. Note that when the non-detection delay unit 106 and the detection delay unit 108 are configured using a computer system as in the present embodiment, the delay time can be adjusted by software, so that adjustment is easy.

  Based on the control signal supplied from the control unit 113, the filter changeover switch 109 receives either one of the signal supplied from the non-detection delay unit 106 and the signal supplied from the detection delay unit 108. This is supplied to the normalization unit 110. The filter changeover switch 109 supplies the signal supplied from the non-detection delay unit 106 to the normalization unit 110 while the non-detection signal is supplied from the control unit 113. On the other hand, the filter changeover switch 109 supplies the signal supplied from the detection delay unit 108 to the normalization unit 110 while the detection signal is supplied from the control unit 113.

  The normalizing unit 110 normalizes the signal supplied from the filter changeover switch 109. For example, the normalization unit 110 acquires the maximum value of a predetermined number (for example, 100) of sampling data (absolute value of signal level) acquired last. Then, the normalization unit 110 divides the acquired sampling data by the maximum value and outputs the result.

  The signal extraction BPF 111 extracts the frequency component of the tone frequency ftone from the signal supplied from the normalization unit 110. The signal extraction BPF 111 is a narrow band BPF having a gain characteristic peak at the tone frequency ftone, and has a gain characteristic as shown in FIG. 5, for example. As shown in FIGS. 4 and 5, the signal extraction BPF 111 is a narrow-band bandpass filter having a large Q value as compared with the detection BPF 107 and greatly attenuates frequency components of frequencies other than the tone frequency ftone.

  The signal strength detection unit 112 detects the strength of the signal supplied from the signal extraction BPF 111. The signal intensity detection unit 112 is, for example, a moving average of the absolute value of the signal level of the supplied signal, a moving average of the square of the signal level of the supplied signal, and a movement of the square sum of the IQ components of the supplied signal. The average is obtained as the signal intensity.

  The control unit 113 determines the presence or absence of a tone signal based on the signal strength detected by the signal strength detection unit 112. For example, the control unit 113 determines whether or not the signal strength exceeds a predetermined threshold, and outputs a detection signal when determining that the signal strength exceeds the predetermined threshold, and the signal strength is predetermined. If it is determined that the threshold value is not exceeded, a non-detection signal is output. The control unit 113 supplies the detection signal or the non-detection signal to the sound reproduction switch 80 and the filter changeover switch 109.

  The audio reproduction switch 80 opens the squelch while the detection signal is supplied from the control unit 113, and closes the squelch while the non-detection signal is supplied from the control unit 113.

  The filter changeover switch 109 supplies the signal supplied from the detection delay unit 108 to the normalization unit 110 and the non-detection signal from the control unit 113 while the detection signal is supplied from the control unit 113. In the meantime, the signal supplied from the non-detection time delay unit 106 is supplied to the normalization unit 110.

  As described above, the filter changeover switch 109 supplies the normalization unit 110 with a signal that has passed through different filters depending on whether the tone signal is detected or not. For this reason, the tone signal detection device 100 gives priority to lowering the probability of false detection due to noise, or lowering the probability of overlooking the tone signal, depending on whether the tone signal is detected or not. It is possible to detect a tone signal by switching whether to give priority to this.

  Hereinafter, how the signal output from the image removal BPF 104 is attenuated will be described in detail with reference to FIGS. 6 and 7. FIG. 6A to 6D and FIGS. 7A to 7D show the signal level of each frequency component with the horizontal axis representing frequency (Hz) and the vertical axis representing signal level.

  First, with reference to FIG. 6, how the signal is attenuated when no tone signal is detected (when no tone signal is detected yet) will be described. Here, a case will be described in which the demodulated signal does not include a tone signal and a frequency component due to noise exists in the tone frequency ftone.

  As shown in FIG. 6A, the signal output from the image removal BPF 104 has a large signal level at the tone frequency ftone due to noise, but the signal level at other frequencies also has a certain large value due to noise.

  As shown in FIG. 6B, the signal level output from the non-detection BPF 105 is relatively higher in the signal level near the tone frequency ftone than in the signal level at the tone frequency ftone. Here, the frequency in the vicinity of the tone frequency ftone is a frequency that does not include the tone frequency ftone.

  Further, as shown in FIG. 6C, the signal output from the normalization unit 110 has a signal level at a frequency near the tone frequency ftone rather than the signal level at the tone frequency ftone, although the signal level is normalized. Remains relatively large.

  Here, as shown in FIG. 6D, the signal level output from the signal extraction BPF 111 has a very low signal level other than the tone frequency ftone. Here, although the frequency component of the tone frequency ftone remains, the signal level is not so high. The reason is that the normalization unit 110 normalizes the signal level of the frequency larger than the signal level of the tone frequency ftone so that the signal level becomes a predetermined value, so that the signal level of the tone frequency ftone becomes relatively small. .

  As described above, when the tone signal is not detected, even if a frequency component due to noise is mixed in the tone frequency ftone, the signal strength detected by the signal strength detection unit 112 does not become so large. For this reason, the probability that the control unit 113 erroneously determines that the frequency component due to noise is a tone signal can be reduced.

  Next, how the signal is attenuated when the tone signal is detected (after the tone signal is once detected) will be described with reference to FIG. Here, a case will be described in which a demodulated signal includes a tone signal and further includes noise similar to that described above.

  As shown in FIG. 7A, the signal output from the image removal BPF 104 has a large signal level at the tone frequency ftone due to the tone signal, but the signal levels at other frequencies also have a certain large value due to noise. .

  As shown in FIG. 7B, the signal level output from the BPF 107 at the time of detection has a relatively higher signal level at the tone frequency ftone than a signal level at a frequency near the tone frequency ftone.

  Further, as shown in FIG. 7C, the signal output from the normalizing unit 110 has a signal level normalized, but the signal level of the tone frequency ftone is a signal having a frequency near the tone frequency ftone. It remains relatively larger than the level.

  Here, as shown in FIG. 7D, the signal output from the signal extraction BPF 111 has a very low signal level at frequencies other than the tone frequency ftone. Here, the signal level of the tone frequency ftone increases. The reason is that the normalization unit 110 normalizes the signal level of the tone frequency ftone so as to be a predetermined value, and thus the signal level of the tone frequency ftone becomes relatively high.

  As described above, once the tone signal is detected, if the tone frequency ftone has a frequency component, the signal strength detected by the signal strength detection unit 112 becomes a large value. For this reason, after detecting the tone signal once, the tone signal detecting apparatus 100 can reduce the probability of overlooking the tone signal. That is, the receiving apparatus 1000 can reduce the probability of erroneously blocking the squelch after opening the squelch once.

  As described above, according to the tone signal detection apparatus 100 according to the present embodiment, when the tone signal is not detected, the false detection of the tone signal due to noise is reduced, and once the tone signal is detected, the tone signal is detected. It is possible to reduce the probability of oversight. Even before the tone signal is detected, it is possible to detect the tone signal as long as the signal level of the frequency near the tone frequency ftone due to noise does not increase. Even after the tone signal is detected, if there is no tone signal, no false detection will occur unless the signal level of the frequency near the tone frequency ftone increases due to noise.

  As described above, the tone signal detection apparatus 100 according to the present embodiment switches between the filter used when the tone signal is detected and the filter used when the tone signal is not detected. For this reason, it is possible to reduce the false detection of the tone signal due to noise until the tone signal is detected, and to reduce the probability of overlooking the tone signal once the tone signal is detected.

  In the above embodiment, the tone signal detection device 100 has been described as having a configuration including the noise removal BPF 101 and the image removal BPF 104. However, for example, when the demodulated signal is handled as a complex signal, the tone signal detection apparatus 100 may be configured not to include the noise removal BPF 101 and the image removal BPF 104. In such a configuration, even if the frequency is shifted in the frequency shift unit 102, an image signal is not generated.

  In the above-described embodiment, an example in which the filter 1 and the filter 2 are connected in series to configure the non-detecting BPF 105 has been described. However, as long as the gain characteristic as shown in FIG. 4A is obtained, the non-detection BPF 105 may have any configuration. For example, the filter 1 and the filter 2 may be connected in parallel, and an adder or a subtracter may be used to add or subtract the outputs of the two filters.

  In the above embodiment, the normalization unit 110 has shown an example in which the signal level of the supplied signal is normalized by dividing it by the maximum value of the past signal level. However, the normalization unit 110 may normalize using another normalization method. For example, the normalization unit 110 normalizes the signal by dividing the signal level of the supplied signal by the signal strength. In this case, the normalization unit 110 may be configured to have a function equivalent to that of the signal strength detection unit 112. Alternatively, the normalization unit 110 supplies data to the signal strength detection unit 112 to detect the signal strength, and the detected signal. It may be configured to receive strength. The signal strength here is, for example, a moving average of the absolute values of the signal level of the supplied signal.

  The normalization unit 110 may normalize the signal by binarizing the signal level of the supplied signal. The normalization unit 110 binarizes depending on whether the signal level of the supplied signal is higher than a predetermined value, for example, “0”. In this case, for example, the normalization unit 110 generates a signal (hereinafter referred to as “−10” as the signal level when the signal level of the supplied signal is a negative value, and “10” when the signal level as the positive signal level). , “Rectangular wave”) is supplied to the signal extraction BPF 111.

  This rectangular wave is a rectangular wave whose fundamental wave is a frequency having the highest signal level among the frequency components of the signal supplied from the filter changeover switch 109 to the normalization unit 110.

  Here, the non-detection BPF 105 used when no tone signal is detected has a higher gain at frequencies near the tone frequency ftone than at the tone frequency ftone. Therefore, if the frequency component due to noise is in the frequency region near the tone frequency ftone, the signal output from the BPF 105 at the time of non-detection has the highest frequency component near the tone frequency ftone.

  Accordingly, the frequency in the vicinity of the tone frequency ftone is a fundamental wave of a rectangular wave. Here, in the rectangular wave, frequency components other than the fundamental wave are small. For this reason, even if the signal extraction BPF 111 extracts the frequency component of the tone frequency ftone from the rectangular wave, the extracted frequency component becomes small. Therefore, the signal intensity detected by the signal intensity detection unit 112 is reduced, and the probability that the control unit 113 erroneously detects a frequency component due to noise as a tone signal can be reduced.

  On the other hand, in detection BPF 107 used when a tone signal is detected, the gain at tone frequency ftone is higher than the gain at frequencies near tone frequency ftone. For this reason, even if the frequency component due to noise is in the frequency region near the tone frequency ftone, the signal output from the BPF 107 at the time of detection has the highest frequency component of the tone frequency ftone.

  Therefore, this tone frequency ftone is a fundamental wave of a rectangular wave. For this reason, when the signal extraction BPF 111 extracts the frequency component of the tone frequency ftone from the rectangular wave, the extracted frequency component becomes large. Therefore, the signal strength detected by the signal strength detection unit 112 is increased, the probability that the control unit 113 misses the tone signal can be lowered, and the probability that the squelch is erroneously blocked can be lowered.

  Further, in the case of normalizing the signal level of the supplied signal by binarization, the normalizing unit 110 is compared to the case of normalizing by dividing the signal level of the supplied signal by the maximum value of the past signal level. This simplifies the configuration and reduces the amount of processing.

  Also, the amount of processing can be reduced by downsampling before normalization. In this case, the tone signal detection apparatus 100 includes a downsampling unit between the filter changeover switch 109 and the normalization unit 110. Then, the tone signal detection apparatus 100 is configured such that a signal is supplied from the filter changeover switch 109 to the normalization unit 110 via the downsampling unit.

  The down-sampling unit down-samples the signal supplied from the filter changeover switch 109 at a sampling frequency 1 / N of the sampling frequency fs (hereinafter referred to as “down-sampling frequency”) fds (Hz).

  When normalization is performed by downsampling in normalization section 110, signal extraction BPF 111 is configured to extract the frequency component of tone frequency fdtone after downsampling.

  When the normalization unit 110 performs binarization by downsampling, the rectangular wave output from the normalization unit 110 is a rectangular wave having the tone frequency fdtone (Hz) after downsampling as a fundamental frequency. . Therefore, the rectangular wave output from the normalization unit 110 includes harmonic components that are odd multiples of the tone frequency fdtone after downsampling, and among these, the third, fifth, and seventh harmonic components are particularly important. Many are included. For this reason, the downsampling frequency fds and the tone frequency fdtone after downsampling are set so that the influence of the third-order, fifth-order, and seventh-order harmonic components is made as difficult as possible.

  For example, in consideration of aliasing at 1/2 of the downsampling frequency fds and 0 (Hz), the tone frequency fdtone after downsampling is 1/4, 1/6, 1 / of the downsampling frequency fds. Both frequencies are set so as not to be 8.

  In the above-described embodiment, the program is described as being stored in advance in a memory or the like. However, the program for causing the tone signal detection apparatus to operate as all or part of the entire apparatus such as the receiving apparatus 1000 or to execute the above-described processing is stored on a flexible disk, a CD-ROM (Compact Disk Read-Only). Memory), DVD (Digital Versatile Disk), MO (Magneto Optical Disk), etc. are stored in a computer-readable recording medium and distributed, installed on another computer and operated as the above-mentioned means, or These steps may be executed.

  Furthermore, the program may be stored in a disk device or the like included in a server device on the Internet, and may be downloaded onto a computer by being superimposed on a carrier wave, for example.

  Further, the tone signal detection apparatus according to the above-described embodiment has been described as being configured using a computer system including a CPU or a DSP and processing a digital signal supplied from the audio signal removal LPF 65. However, the tone signal detection apparatus according to the present invention may be configured such that each component is configured by an analog circuit or the like, or may process an analog signal supplied from the audio signal removal LPF 65.

  In this case, the noise removal BPF 101, the image removal BPF 104, the non-detection BPF 105, the detection BPF 107, and the signal extraction BPF 111 are configured by, for example, a filter circuit including a capacitive element, a resistor, and the like. The frequency shift unit 102 is configured using, for example, a multiplier. The local oscillator 103 is composed of, for example, an oscillation circuit provided with a crystal oscillator. The non-detection delay unit 106 and the detection delay unit 108 are configured using, for example, a delay circuit. The filter changeover switch 109 is constituted by, for example, a semiconductor switch or a relay. The normalization unit 110 is configured using, for example, a storage circuit, a comparison circuit, and a division circuit. The signal intensity detection unit 112 is configured using, for example, an integration circuit. The control unit 113 is configured using, for example, a comparison circuit.

It is a block diagram which shows the structure of a receiver provided with the tone signal detection apparatus which concerns on this embodiment. It is a block diagram which shows the structure of the tone signal detection apparatus which concerns on this embodiment. It is a figure for demonstrating the gain characteristic of non-detection BPF and detection BPF. (A) is a figure which shows an example of the gain characteristic of BPF at the time of non-detection. (B) is a figure which shows an example of the gain characteristic of BPF at the time of a detection. It is a figure which shows an example of the gain characteristic of signal extraction BPF. (A)-(D) is a figure for demonstrating how a signal attenuate | damps by each BPF when the tone signal is not detected. (A)-(D) is a figure for demonstrating how a signal attenuate | damps by each BPF when the tone signal is detected.

Explanation of symbols

100 tone signal detection apparatus 101 noise removal BPF
102 Frequency shift unit 103 Local oscillator 104 Image removal BPF
105 BPF when not detected
106 Non-detection delay unit 107 Detection BPF
108 Detection delay unit 109 Filter changeover switch 110 Normalization unit 111 Signal extraction BPF
112 Signal Strength Detection Unit 113 Control Unit

Claims (8)

A tone signal detection device for detecting a tone signal of a predetermined frequency included in an input signal,
A first filter having a gain peak at a frequency higher and lower than the frequency of the tone signal ;
Have a different gain characteristic to the first filter, a second filter having a frequency substantially gain peak of the same frequency of the tone signal,
Extraction means for extracting a frequency component of a frequency corresponding to the tone signal from the supplied signal;
It is determined whether the signal intensity of the signal extracted by the extraction means exceeds a predetermined value, and when it is determined that the signal intensity of the signal does not exceed the predetermined value, a non-detection signal is output, Discriminating means for outputting a detection signal when it is determined that the signal intensity of the signal exceeds a predetermined value;
A signal obtained by applying an input signal to the first filter is supplied to the extraction unit while the non-detection signal is output by the determination unit, and an input is performed while the detection signal is output by the determination unit. Supply means for supplying a signal obtained by applying a signal to the second filter to the extraction means;
A tone signal detection apparatus characterized by the above. The first filter includes a first band pass filter having a gain peak at a frequency higher than the frequency of the tone signal and a second band pass filter having a gain peak at a frequency lower than the frequency of the tone signal. Consisting of a combination of
The tone signal detection apparatus according to claim 1 , wherein The extraction means includes normalization means for normalizing the signal level of the supplied signal, normalizes the supplied signal by the normalization means, and corresponds to the frequency of the tone signal from the normalized signal. Extract frequency components,
The tone signal detection apparatus according to claim 1 or 2 , characterized in that The normalizing means normalizes the signal level of the supplied signal by binarizing it using a predetermined threshold value.
The tone signal detection apparatus according to claim 3 , wherein The normalization means determines a reference value indicating the intensity of the signal based on the signal level of the supplied signal, and normalizes by dividing the signal level of the supplied signal by the reference value.
The tone signal detection apparatus according to claim 3 , wherein The supply means further includes delay means for making the delay time of the signal that has passed through the first filter substantially the same as the delay time of the signal that has passed through the second filter,
Tone signal detecting apparatus according to any one of claims 1 to 5, characterized in that. A tone signal detection method for detecting a tone signal having a predetermined frequency included in an input signal, wherein the tone signal detection method has a first gain peak at a frequency higher and lower than the frequency of the tone signal . and a filter, said to have a different gain characteristic to the first filter, a second filter having a frequency substantially gain peak of the same frequency of the tone signal, extraction means, and determination means, supplied And a tone signal detection apparatus comprising: means for detecting a tone signal;
The extraction means extracts a frequency component of a frequency corresponding to the tone signal from the supplied signal;
Non-detection when the determination means determines whether the signal intensity of the signal extracted by the extraction means exceeds a predetermined value, and determines that the signal intensity of the signal does not exceed the predetermined value When a signal is output and it is determined that the signal strength of the signal exceeds a predetermined value, a detection signal is output,
While the non-detection signal is output by the determination unit, the supply unit supplies a signal obtained by applying an input signal to the first filter to the extraction unit, and the detection signal is output by the determination unit. A signal obtained by applying an input signal to the second filter while the signal is supplied to the extraction means.
And a tone signal detecting method. Computer
A program for functioning as a tone signal detection device for detecting a tone signal of a predetermined frequency included in an input signal,
The program runs the computer
A first filter having a gain peak at a frequency higher and lower than the frequency of the tone signal ;
The have a different gain characteristic to the first filter, a second filter having a frequency substantially gain peak of the same frequency of the tone signal,
Extraction means for extracting a frequency component of a frequency corresponding to the tone signal from the supplied signal;
It is determined whether the signal intensity of the signal extracted by the extraction means exceeds a predetermined value, and when it is determined that the signal intensity of the signal does not exceed the predetermined value, a non-detection signal is output, Discrimination means for outputting a detection signal when it is determined that the signal intensity of the signal exceeds a predetermined value;
A signal obtained by applying an input signal to the first filter is supplied to the extraction unit while the non-detection signal is output by the determination unit, and an input is performed while the detection signal is output by the determination unit. Supply means for supplying a signal obtained by applying a signal to the second filter to the extraction means;
A program characterized by functioning as

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