JP2009267544A - Tone signal detector, tone signal detection method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tone signal detector for preventing false detection of a tone signal, and to provide a tone signal detection method and a program. <P>SOLUTION: Upon selection of the frequency of a tone signal, a local oscillator 13 generates a frequency signal S13 having a shift frequency f13 corresponding to the frequency of this tone signal. A frequency shifter 12 shifts a frequency of the tone signal based on the frequency signal S13 to a passband of a BPF16. A BPF 14 removes an image signal from the frequency-converted signal S12 which the frequency shifter 12 generated, and a normalizer 15 normalizes the amplitude of the signal S14. By this, even if the amplitude of the tone signal is small, the amplitude thereof is unified to a suitable magnitude. For this reason, even if there is a difference in the amplitude of the tone signal, the tone signal can be detected reliably and an false detection can be prevented. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tone signal detection apparatus, a tone signal detection method, and a program.

  In an analog wireless device, a tone squelch method is used to remove noise generated when there is no signal and to avoid interference with a wireless device using a signal of the same frequency.

  A transmitter using this tone squelch method transmits a tone signal (or CTCSS signal, CTCSS; Continuous Tone Code Squelch System) with a frequency outside the voice band superimposed on a voice signal having a voice band of 300 Hz to 3 kHz.

  A receiver that receives such a signal demodulates the received signal to detect a tone signal, and when the detected tone signal frequency matches the squelch frequency set by the local station, opens the tone squelch, and receives sound from the speaker. Output.

  For such tone signals, as frequency signals outside the voice band, for example, 67.0 Hz, 151.4 Hz, 156.7 Hz, 183.5 Hz, 186.2 Hz, 210.7 Hz, 218.1 Hz, 254.1 Hz, etc. These signals are used.

Conventionally, as a tone squelch detection device for detecting a tone signal, the frequency of the tone signal is shifted to a certain frequency, and this signal is passed through a band-pass filter of a pass band including the certain frequency, so that the tone signal of each frequency. (For example, refer to Patent Document 1).
Japanese Utility Model Publication No. 63-97928 (page 3-4, FIG. 1)

  However, in such a conventional tone squelch detection device, the tone signal is erroneously detected when there is a difference in the amplitude of the tone signal at each frequency depending on the communication status such as the difference in the output of the transmitting side radio or the radio wave environment. Or it may not be detected.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a tone signal detection device, a tone signal detection method, and a program capable of preventing erroneous detection of a tone signal. .

In order to achieve this object, a tone signal detection apparatus according to the first aspect of the present invention provides:
A frequency signal generator that generates a frequency signal of a moving frequency that moves the frequency of the tone signal to a preset frequency band;
A frequency conversion unit that generates a frequency conversion signal by moving the frequency of the input signal including the tone signal by the moving frequency of the frequency signal generated by the frequency signal generation unit;
A normalization processing unit that normalizes the amplitude of the frequency conversion signal generated by the frequency conversion unit to generate a normalized signal;
A passband is set to a frequency band of the tone signal included in the normalized signal generated by the normalization processing unit, and a filter that filters the normalized signal;
And a tone signal detector that detects the tone signal based on the signal filtered by the filter.

  The normalization unit determines a reference value indicating an intensity based on the amplitude of the frequency conversion signal generated by the frequency conversion unit, and divides the frequency conversion signal by the reference value to thereby calculate the frequency conversion signal. The amplitude may be normalized.

  The normalization unit may normalize the amplitude of the frequency conversion signal by adjusting and binarizing the amplitude of the frequency conversion signal generated by the frequency conversion unit.

A downsampling unit for downsampling the frequency conversion signal generated by the frequency conversion unit;
The normalization unit normalizes the amplitude of the frequency conversion signal downsampled by the downsampling unit,
The filter may have a pass band set to a frequency band of the tone signal included in the normalized signal.

The tone signal detection method according to the second aspect of the present invention is:
Generating a frequency signal of a moving frequency that moves the frequency of the tone signal to a preset frequency band;
Generating a frequency conversion signal by moving the frequency of the input signal including the tone signal by the moving frequency of the generated frequency signal;
Normalizing the amplitude of the generated frequency conversion signal to generate a normalized signal;
Filtering the normalized signal with a filter whose passband is set to the frequency band of the tone signal included in the generated normalized signal;
Detecting the tone signal based on the signal filtered by the filter.

The program according to the third aspect of the present invention is:
On the computer,
A procedure for generating a frequency signal of a moving frequency for moving the frequency of the tone signal to a preset frequency band;
A step of generating a frequency conversion signal by moving the frequency of the input signal including the tone signal by the moving frequency of the generated frequency signal;
A procedure for generating a normalized signal by normalizing the amplitude of the generated frequency conversion signal,
Filtering the normalized signal with a filter whose passband is set to the frequency band of the tone signal included in the generated normalized signal;
Detecting the tone signal based on the signal filtered by the filter;
Is to execute.

  According to the present invention, it is possible to prevent erroneous detection of a tone signal.

  Hereinafter, a tone signal detection apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a case where the tone signal detection apparatus is applied to a receiver will be described.

(Embodiment 1)
The configuration of the receiver 100 according to the first embodiment is shown in FIG.
The receiver 100 includes an intermediate frequency amplifier 1, a demodulator 2, a low frequency amplifier 3, a switch 4, an HPF (high pass filter) 5, a power amplifier 6, a speaker 7, and an LPF (low pass filter) 8. And tone signal detection device 9.

  The intermediate frequency amplifier 1 is supplied with the intermediate frequency signal Sin and amplifies the intermediate frequency signal Sin, and supplies the demodulator 2 with a signal S1 obtained by amplifying the intermediate frequency signal Sin.

  The demodulator 2 converts the signal S1 supplied from the intermediate frequency amplifier 1 into a low frequency signal S2.

  The low frequency amplifier 3 amplifies the low frequency signal S2 converted by the demodulator 2 to generate a signal S3.

  The switch 4 is controlled by a control signal S9 supplied from the tone signal detection device 9, and is closed or opened. When the switch 4 is closed, the signal S3 generated by the low frequency amplifier 3 is supplied to the HPF 5, and when the switch 4 is opened, the supply of the signal S3 to the HPF 5 is stopped.

  The HPF 5 is a filter that removes the low-frequency component tone signal St from the signal S3 output from the low-frequency amplifier 3 and passes the audio signal when the switch 4 is closed.

  The cutoff frequency of HPF 5 is set to be higher than the frequency of tone signal St and lower than the frequency band of the audio signal. The HPF 5 supplies the signal S5 subjected to such filter processing to the power amplifier 6.

  The power amplifier 6 is for amplifying the power of the signal S5 supplied from the HPF 5, and supplies the power amplified signal S6 to the speaker 7.

  The speaker 7 outputs sound based on the signal S6 amplified by the power amplifier 6.

  The LPF 8 attenuates an audio band component from the low frequency signal S2 converted by the demodulator 2 and supplies the signal S8 to the tone signal detection device 9.

  The tone signal detection device 9 samples the signal S8 supplied from the LPF 8 at the sampling rate Fs and detects the tone signal St. The tone signal detection device 9 generates a control signal S9 based on the detection result, and generates the control signal S9. Based on this, the switch 4 is opened and closed.

  The tone signal detection device 9 is configured to normalize the amplitude of the frequency conversion signal obtained by converting the tone frequency of the tone signal St in order to prevent erroneous detection of the tone signal St.

  As shown in FIG. 2, the tone signal detection device 9 includes a BPF 11, a frequency shift unit 12, a local oscillator 13, a BPF 14, a normalization processing unit 15, a BPF 16, a signal intensity detection unit 17, and a control unit. 18.

  The BPF 11 is a band-pass filter having a pass band of the tone frequency of the tone signal St, and further attenuates a voice band component remaining in the signal S8 by performing band limitation on the signal S8 supplied from the LPF 8. The BPF 11 performs such filter processing and supplies the signal S11 to the frequency shift unit 12.

  The frequency shift unit 12 moves (shifts) the frequency of the signal S11 as an input signal including the tone signal St by the moving frequency of the frequency signal S13 supplied from the local oscillator 13 to generate the frequency conversion signal S12. It is.

  The frequency shift unit 12 shifts the frequency of the signal S11 by multiplying the signal S11 and the frequency signal S13 or adding the signal S11 and the frequency signal S13 and outputting the result through a nonlinear element. In the first embodiment, the frequency shift unit 12 includes a multiplier (not shown) that multiplies the signal S11 and the frequency signal S13.

・・・・・・・・・（１）
When multiplying the signal S11 and the frequency signal S13, the frequency conversion signal S12 output by the frequency shift unit 12 is expressed by the following equation (1).

... (1)

  The first term of the formula (1) indicates a signal having a frequency that is the sum of the frequency f11 and the frequency Δf, and the second term indicates a signal having a frequency that is the difference between the frequency f11 and the frequency Δf. By acquiring the signal of the first term, the frequency f11 of the signal S11 is shifted.

  In the first embodiment, when the tone frequency of the tone signal St is set as ft, the frequency shift is performed so that the tone frequency ft moves. Assuming that the frequency after the shift of the tone frequency ft is fts1, this frequency fts1 is set to a frequency higher than the frequency 0 to 300 Hz where the tone signal St exists in order to be less affected by noise and image signals. desirable. In addition, it is desirable that components outside the frequency band such as noise are sufficiently attenuated by the BPF 11.

  When the frequency signal S13 is supplied from the local oscillator 13, the frequency shift unit 12 multiplies the signal S11 and the frequency signal S13, and supplies the frequency conversion signal S12 obtained by moving the frequency f11 of the signal S11 to the BPF 14.

  The local oscillator 13 generates a frequency signal S13 for moving the frequency of the tone signal St included in the low frequency signal S2 to a preset frequency band. The local oscillator 13 is configured by a frequency synthesizer such as a DDS (Direct Digital Synthesizer), a crystal oscillator, or the like.

  In the first embodiment, the tone signal St can be detected by one BPF 16 even when the tone frequency of the tone signal St can be selected and set from a plurality of values or when the tone frequency ft can be changed. Therefore, the frequency Δf is determined based on the difference between the set tone frequency ft and the center frequency fb of the pass band of the BPF 16.

  That is, as shown in FIG. 3, when detecting the tone signal St of the tone frequencies ft1, ft2,..., Δf is the moving frequency (shift amount), and the shifted frequency fts1 is the center frequency fb of the pass band of the BPF 16. .DELTA.f = .DELTA.f1, .DELTA.f2,...

  When the local oscillator 13 supplies the thus determined moving frequencies Δf1, Δf2,... To the frequency shift unit 12, the frequency shift unit 12 uses the tone frequencies ft1, ft2,. Shift to fts1. In this way, one BPF 16 can be configured. The local oscillator 13 may store frequency table data as shown in FIG.

  The BPF 14 is a filter for removing the frequency component of the image signal generated by the frequency shift unit 12 shifting the frequency. The second term of Equation (1) represents this image signal, and when the frequency shift unit 12 shifts the frequency f11 of the signal S11, an image signal having a frequency (f11-f13) is generated.

  The BPF 14 removes the image signal and supplies the removed signal S14 to the normalization processing unit 15. In the case of processing using a complex signal, the image signal is not generated, so the BPF 14 is not always necessary.

  In order to prevent erroneous detection, the normalization processing unit 15 normalizes and equalizes the amplitude of the signal S14 obtained by removing the image signal from the frequency conversion signal S12 generated by the frequency shift unit 12, and generates the normalized signal S15. Is.

  For example, as illustrated in FIG. 5, the normalization processing unit 15 according to the first embodiment determines a reference value Sref indicating the intensity based on the amplitude of the signal S14 generated by the frequency shift unit 12 and supplied from the BPF 14, By dividing the signal S14 by the reference value Sref, the amplitude of the signal S14 is normalized to generate a normalized signal S15.

  When the normalization processing unit 15 performs such normalization processing, the amplitude is made uniform as shown in FIG.

  When the amplitude is made uniform in this way, the amplitude is normalized to an appropriate magnitude even when there is a difference in the amplitude of the tone signal St depending on the communication state such as the difference in the output of the transmitting side radio device or the radio wave environment. Therefore, the tone signal St is reliably detected, and erroneous detection is prevented. The normalization processing unit 15 supplies the normalization signal S15 generated by performing the normalization process in this way to the BPF 16.

  The BPF 16 is a filter that filters the normalized signal S15 supplied from the normalization processing unit 15 with the frequency fb as the center frequency.

  As described above, the moving frequency Δf is determined based on the value ft set as the frequency of the tone signal St, and the local oscillator 13 supplies the frequency signal S13 having the moving frequency Δf to the frequency shift unit 12. Even when the frequency of the tone signal St can be selected and set from a plurality of values or when the tone frequency is changed, the receiver 100 only needs to have one BPF 16 for detecting the intensity of the tone signal St. become. The BPF 16 supplies the signal S16 subjected to such filter processing to the signal strength detection unit 17.

  The signal intensity detection unit 17 detects the signal intensity S17 of the tone signal St from the signal S16 supplied from the BPF 16. The signal strength detection unit 17 detects the signal strength S17 of the tone signal St by performing an arithmetic process for averaging the absolute values. Note that the signal strength detection unit 17 may detect the signal strength S17 of the tone signal St by performing arithmetic processing such as averaging of squares and the sum of squares of IQ components. The signal strength detection unit 17 supplies the detected signal strength S17 to the control unit 18.

  The control unit 18 controls the switch 4 based on the signal strength S17 supplied from the signal strength detection unit 17.

  The control unit 18 compares the signal strength of the tone signal St with a preset threshold value Sth, and determines whether the signal strength of the tone signal St is greater than or equal to the preset threshold value Sth.

  When the signal intensity S17 of the tone signal St is greater than or equal to the threshold value Sth, the control unit 18 outputs a control signal for closing the switch 4 to the switch 4. On the other hand, when the signal strength of the tone signal St is less than the threshold value Sth, the control unit 18 outputs a control signal for opening the switch 4 to the switch 4.

  The control unit 18 outputs a control signal for closing the switch 4 to the switch 4 when the signal strength S17 of the tone signal St is equal to or higher than the threshold value Sth, and opens the switch 4 when not outputting the control signal to the switch 4. You can also make it.

  Next, the operation of the receiver 100 according to the first embodiment will be described when the frequency of the tone signal St is set as ft1.

  When receiving the received signal, the receiver 100 supplies the intermediate frequency signal Sin to the intermediate frequency amplifier 1.

  The intermediate frequency amplifier 1 amplifies the intermediate frequency signal Sin and supplies the amplified signal S1 to the demodulator 2.

  The demodulator 2 converts the signal S1 supplied from the intermediate frequency amplifier 1 into a low frequency signal S2, and the low frequency amplifier 3 amplifies the low frequency signal S2 converted by the demodulator 2 to generate a signal S3. .

  On the other hand, the low-frequency signal S2 converted by the demodulator 2 is supplied to the LPF 8. As shown in FIG. 6, the low frequency signal S2 is a signal in which a tone signal St having a frequency ft1 is superimposed on an audio signal Sound having a frequency of 300 Hz to 3000 Hz.

  The LPF 8 supplies the tone signal detection device 9 with the signal S8 in which the audio band component is suppressed in the low frequency signal S2. The tone signal detection device 9 samples the signal S8 supplied from the LPF 8 at the sampling rate Fs.

  As shown in FIG. 7A, the BPF 11 of the tone signal detection device 9 performs band limitation on the signal S8 supplied from the LPF 8, thereby reducing the audio band component remaining in the signal S8 supplied from the LPF 8. Further attenuate. This audio band component remains as an out-of-frequency band component n1 such as noise, but it is desirable that it is sufficiently attenuated.

  When detecting the tone signal St having the frequency ft1, the moving frequency Δf1 is determined based on the tone frequency ft1. The local oscillator 13 generates a frequency signal S13 having the moving frequency Δf1 and supplies the generated frequency signal S13 to the frequency shift unit 12.

  As shown in FIG. 7B, the frequency shifter 12 multiplies the signal S11 and the frequency signal S13 of the moving frequency Δf1 supplied from the local oscillator 13 to thereby change the tone frequency ft1 of the tone signal St to the moving frequency. Shift by Δf1.

  When the frequency shift unit 12 shifts the tone frequency ft1 of the tone signal St in this way, the tone frequency ft1 is shifted to the frequency fts1.

  When the frequency shift unit 12 shifts the tone frequency ft1 by the moving frequency Δf1, an image component is generated from the component of the tone frequency ft1. The frequency of the image component is fi1 = ft1-Δf1, but as shown in FIG. 7B, it is folded back at 0 Hz to become the frequency fi2 = | ft1-Δf1 |.

  Further, as shown in FIG. 7B, although the frequency of the noise n1 also changes, there is no problem because even the change is sufficiently suppressed by the BPF 11.

  The BPF 14 removes the image signal and noise of the frequency fi2 by performing band limitation.

  When the BPF 14 removes the image signal, the frequency characteristic becomes a characteristic as shown in FIG. 7C, and the component of the image frequency fi2 becomes small enough to be ignored.

  The normalization processing unit 15 normalizes the intensity of the signal from which the BPF 14 has removed the image frequency, and the BPF 16 extracts the frequency component of the tone signal St. The signal strength detection unit 17 detects the signal strength S17 of the tone signal St extracted by the BPF 16.

  When the signal strength S17 supplied from the signal strength detection unit 17 is equal to or greater than a preset threshold value Sth, the control unit 18 determines that the tone signal St has been detected, and supplies a control signal for closing the switch 4 to the switch 4. .

  When the switch 4 is closed according to the control signal S9, the signal S3 generated by the low-frequency amplifier 3 passes through the switch 4 and is supplied to the HPF 5.

  The HPF 5 cuts the tone signal St and supplies a signal S5 consisting of a sound signal Sound to the power amplifier 6, and the speaker 7 outputs sound based on the signal S6 supplied from the power amplifier 6.

  As described above, when the frequency of the tone signal St1 is set as ft1 and the receiver 100 receives the tone signal St1 having the tone frequency ft1, the signal strength detected by the signal strength detection unit 17 is equal to or greater than a preset threshold value Sth. Thus, the control unit 18 determines that the tone signal St has been detected.

  However, when the frequency of the tone signal St1 is set as ft1, and the receiver 100 receives a tone signal St having a tone frequency ft2 different from the tone frequency ft1, the tone frequency ft2 of the tone signal St is shifted by the moving frequency Δf1. The frequency is ft2 + Δf1 ≠ fts1.

  Therefore, since the frequency obtained by shifting the frequency ft2 by the moving frequency Δf1 is different from the center frequency fb of the BPF 16, the signal intensity S17 detected by the signal intensity detector 17 is less than the threshold value Sth. For this reason, the signal strength detection unit 17 detects the absence of a tone signal.

  As described above, the frequency shift unit 12 multiplies the signal S11 and the frequency signal S13, so that the tone frequency ft is reduced to the center frequency fb of the BPF 16 regardless of the value of the tone frequency ft of the tone signal St. The tone signal St can be detected even if one BPF 16 is shifted.

  As described above, according to the first embodiment, the normalization processing unit 15 normalizes the amplitude of the signal S14 obtained by removing the image signal from the frequency conversion signal S12 generated by the frequency shift unit 12. .

  Therefore, even if the amplitude of the tone signal St is small, the amplitude is unified to an appropriate size by normalization, and the tone signal St is reliably detected even if the amplitude of the tone signal St varies depending on the communication state. And false detection can be prevented.

(Embodiment 2)
In the receiver according to the second embodiment, it is assumed that the tone signal detection device is configured by software, and the tone signal detection device performs normalization by binarizing the signal amplitude, and performs processing time when performing normalization. The downsampling is performed in consideration of the above.

  When the tone signal detecting device 9 is configured by computer software, the computer has processing capability and it is necessary to code in consideration of processing time.

  For this reason, the tone signal detection apparatus 9 according to the second embodiment includes gain adjustment units 21 and 22 and a downsampling unit 23 as shown in FIG.

  Note that the tone signal detection device 9 samples the signal S8 supplied from the LPF 8 at the sampling rate Fs as in the first embodiment.

  The gain adjusting units 21 and 22 adjust the gains of the BPF 11 and the normalization processing unit 15, respectively, in order to improve calculation accuracy.

  The downsampling unit 23 of the second embodiment downsamples the signal S14 output from the BPF 14 at a rate Fs ′ that is 1 / N of the sampling rate Fs, and outputs the signal S23 to the normalization processing unit 15.

  The normalization processing unit 15 according to the second embodiment uses the signal S23 down-sampled by the down-sampling unit 23 (a signal obtained by removing the image signal from the frequency conversion signal S12 generated by the frequency shift unit 12) as the simplest normalization processing. Is normalized by binarizing.

  When the normalization processing unit 15 performs binarization, the normalization signal S15 generated by the normalization processing unit 15 becomes a rectangular wave as shown in FIG.

  In the second embodiment, the center frequency fb 'is set to the frequency fb' centered on the frequency fts1 'obtained by down-sampling the frequency fts1 obtained by shifting the tone frequency ft1 with the center frequency of the BPF 16 as fb'.

  Further, as described above, since the normalized signal S15 is a rectangular wave, an odd multiple of harmonics is generated. Of these, the sampling rate Fs ′ of the down-sampling unit 23 and the frequency fts ′ of the tone signal St after down-sampling are set so that the third-order, fifth-order, and seventh-order harmonics having relatively high intensity do not enter the BPF 16 It is desirable that

  That is, the sampling rate Fs ′ of the downsampling unit 23 is set so that the sampling rate Fs ′ of the downsampling unit 23 is different from 4 times, 6 times, and 8 times the frequency fts ′ of the tone signal St after downsampling. The frequency fts ′ of the tone signal St after downsampling is preferably set.

Next, the operation of the receiver 100 according to the second embodiment will be described.
Assume that the signal S11 obtained by removing the noise n1 from the signal S2 by the BPF 11 has a waveform as shown in FIG.

  This signal S11 includes a tone signal St having a tone frequency ft1. The gain adjustment unit 21 is supplied with the signal S11 from the BPF 11, adjusts the gain of the signal S11, and supplies the gain-adjusted signal S21 to the frequency shift unit 12.

  Similarly to the first embodiment, when ft1 is set as the frequency of the tone signal St, the local oscillator 13 determines the moving frequency Δf based on the tone frequency ft1, and generates and generates the frequency signal S13 of the moving frequency Δf. The frequency signal S13 is supplied to the frequency shift unit 12.

  The frequency shift unit 12 multiplies the signal S21 supplied from the gain adjustment unit 21 and the frequency signal S13 of the moving frequency Δf supplied from the local oscillator 13 to shift the tone frequency ft1 of the tone signal St to the frequency fts1. To do.

  When the frequency shift unit 12 shifts the tone frequency ft1 of the tone signal St to the frequency fts1, the waveform of the frequency conversion signal S12 becomes a waveform as shown in FIG. The frequency conversion signal S12 includes two components, a frequency (ft1 + Δf) and a frequency (ft1-Δf).

  The BPF 14 removes the signal component of the frequency (ft1-Δf) from the frequency components of the frequency (ft1 + Δf) and the frequency (ft1-Δf). When the BPF 14 removes the signal component of the frequency (ft1-Δf), the waveform of the signal S14 becomes a waveform as shown in FIG.

  The downsampling unit 23 downsamples the signal S14 supplied from the BPF 14 at a sampling rate Fs' of 1 / N.

  As shown in FIG. 11A, when the downsampling unit 23 performs downsampling, the tone frequency ft1 of the tone signal St is converted to the frequency fts1 ′, and the waveform of the signal S23 is shown in FIG. The waveform is as shown.

  The normalization processing unit 15 performs binarization processing on the signal S23 sampled by the downsampling unit 23. When the normalization processing unit 15 performs the binarization process, the waveform of the signal S23 becomes a rectangular wave as shown in FIG.

  Further, since the normalized signal S15 is a rectangular wave, as shown in FIG. 11B, the normalized signal S15 includes odd-numbered harmonics Sh.

  The frequency of the harmonic Sh is folded at Fs ′ / 2 and 0 Hz and dispersed in the band. However, if the sampling rate Fs ′ and the frequency fts ′ of the down-sampled tone signal St are set as described above, it is not necessary to consider the influence of the harmonic Sh for detection of the tone signal St.

  The gain adjustment unit 22 performs gain adjustment on the normalized signal S15 output from the normalization processing unit 15, and supplies the gain-adjusted signal S22 to the BPF 16.

  Since the tone signal St having the frequency fts is received, the frequency fts1 'and the center frequency fb' of the BPF 16 coincide with each other as shown in FIG.

  Accordingly, when the BPF 16 performs filtering on the signal S22, the tone signal St having the frequency fts1 'passes through the BPF 16. Therefore, the signal S16 includes the tone signal St having the frequency fts1 ', and the waveform of the signal S16 is as shown in FIG.

  The signal strength detection unit 17 detects the signal strength S17 of the signal S16 by squaring the signal S16 acquired by the BPF 16 and calculating the average, and outputs the signal strength S17 to the control unit 18. When the signal strength S17 supplied from the signal strength detection unit 17 is compared with the threshold value Sth, the signal strength S17 exceeds the threshold value Sth. Therefore, the control unit 18 outputs a control signal and closes the switch 4.

  Next, it is assumed that the signal S11 includes the tone signal St having the tone frequency ft1, and the amplitude of the tone signal St is larger than the waveform shown in FIG. 10A, as shown in FIG. .

  When the tone frequency ft1 of the tone signal St is selected, the local oscillator 13 generates a frequency signal S13 having a moving frequency Δf1 and supplies the frequency signal S13 to the frequency shift unit 12.

  The frequency shift unit 12 multiplies the signal S21 supplied from the gain adjustment unit 21 and the frequency signal S13 of the moving frequency Δf supplied from the local oscillator 13 to shift the tone frequency ft1 of the tone signal St to the frequency fts1. To do.

  When the frequency shift unit 12 shifts the frequency ft1 of the tone signal St, the waveform of the frequency conversion signal S12 becomes a waveform as shown in FIG. The frequency conversion signal S12 includes two components, a frequency (ft1 + Δf) and a frequency (ft1-Δf).

  The BPF 14 removes the signal component of the frequency (ft1-Δf) from the frequency components of the frequency (ft1 + Δf) and the frequency (ft1-Δf). When the BPF 14 removes the signal component of the frequency (ft1-Δf), the signal The waveform of S14 is as shown in FIG.

  The downsampling unit 23 downsamples the signal S14 supplied from the BPF 14 at a sampling rate Fs' of 1 / N. When the downsampling unit 23 downsamples, the frequency of the tone signal St is converted to fts1 ', and the waveform of the downsampled signal S23 becomes a waveform as shown in FIG.

  The normalization processing unit 15 performs binarization processing on the sampled signal S23. When the normalization processing unit 15 performs the binarization process, the waveform of the normalization signal S15 becomes a rectangular wave as shown in FIG.

  When the amplitude of the tone signal St is larger than the amplitude of the tone signal St shown in FIG. 10A, the amplitude of the signal S23 down-sampled by the down-sampling unit 23 also increases as shown in FIG.

  However, as can be seen by comparing the normalized signal S15 shown in FIG. 9 and the normalized signal S15 shown in FIG. 13, the normalization processing unit 15 performs the binarization process, so that the amplitude of the tone signal St is increased. Even if it changes, the amplitude of the normalized signal S15 does not change.

  If the amplitude of the normalized signal S15 does not change, the tone signal St is reliably detected even when there is a difference in the amplitude of the tone signal St depending on the communication state such as the difference in the output of the transmitter radio or the radio wave environment, False detection is prevented.

  When the BPF 16 performs filtering on the signal S22, the waveform of the signal S16 becomes a waveform as shown in FIG. This signal S16 includes a tone signal St of frequency fts1 '.

  The signal strength detection unit 17 detects the signal strength of the signal S16 acquired by the BPF 16, and supplies the detected signal strength to the control unit 18. When the signal strength S17 supplied from the signal strength detection unit 17 is compared with the threshold value Sth, the signal strength S17 exceeds the threshold value Sth. Therefore, the control unit 18 outputs a control signal and closes the switch 4.

  Next, it is assumed that the signal S11 includes the tone signal St of the tone frequency ft2 (ft1 ≠ ft2) instead of the tone frequency ft1. It is assumed that the signal S11 has a waveform as shown in FIG.

  At this time, when the tone frequency ft1 of the tone signal St is selected, the local oscillator 13 determines the moving frequency Δf = fts1−ft1 based on the tone frequency ft1, and generates the frequency signal S13 having the moving frequency Δf. The frequency signal S <b> 13 is supplied to the frequency shift unit 12.

  The frequency shift unit 12 multiplies the frequency of the signal S21 supplied from the gain adjustment unit 21 by the frequency of the moving frequency S13 supplied from the local oscillator 13, thereby shifting the tone frequency ft2 of the tone signal St. The waveform of the shifted frequency conversion signal S12 is as shown in FIG.

  The BPF 14 removes the frequency (ft2-Δf) component from the frequency (ft2 + Δf) component and the frequency (ft2-Δf) component. When the BPF 14 removes the signal having the frequency (ft2-Δf), the waveform of the signal S14 becomes a waveform as shown in FIG.

  The downsampling unit 23 downsamples the signal S14 supplied from the BPF 14 at the sampling rate Fs ′. When the downsampling unit 23 performs downsampling, the tone frequency ft2 of the tone signal St becomes the frequency fts2 ', and the waveform of the downsampled signal S23 becomes a waveform as shown in FIG.

  The normalization processing unit 15 performs binarization processing on the signal S23. When the normalization processing unit 15 performs the binarization process, the waveform of the normalization signal S15 becomes a rectangular wave as shown in FIG.

  The BPF 16 performs a filtering process on the signal S22. The tone frequency of the tone signal St included in the signal S11 is ft2, which is different from the tone frequency ft1 of the tone signal St set by the receiver 100.

  For this reason, since the center frequency fb 'of the BPF 16 and the frequency fts2' do not coincide with each other, the signal S16 does not include the tone signal St of the frequency fts2 '. Therefore, the amplitude of the signal S16 output from the BPF 16 is reduced, and the waveform is as shown in FIG.

  The signal strength detection unit 17 detects the signal strength S17 of the signal S16 that has passed through the BPF 16, and supplies the detected signal strength S17 to the control unit 18. The control unit 18 compares the signal strength S17 supplied from the signal strength detection unit 17 with the threshold value Sth. Since the amplitude of the signal S16 becomes small as shown in FIG. 14 (f), the signal intensity S17 becomes less than the threshold value Sth.

  Since the signal strength S17 supplied from the signal strength detection unit 17 is less than the threshold value Sth, the control unit 18 determines that the tone signal St is not detected, and outputs a control signal for closing the switch 4 to the switch 4. There is no.

  Accordingly, since the switch 4 remains open, no sound is output from the speaker 7.

  As described above, if the tone frequency ft2 of the received tone signal St and the tone frequency ft1 set as the frequency of the tone signal St do not match, the tone signal detection device indicates that the supplied signal Sin is not a desired signal. 9 will be judged.

  As described above, according to the second embodiment, the normalization processing unit 15 performs downsampling, and binarizes the downsampled signal S23 as normalization processing.

  Therefore, the tone signal St can be detected by a process suitable for the processing capability and calculation accuracy of the computer.

  Also, by binarization, the signal S14 obtained by removing the image signal from the frequency conversion signal S12 can be converted into a rectangular wave by the simplest method.

  In carrying out the present invention, various forms are conceivable and the present invention is not limited to the above embodiment.

  For example, the tone signal detection apparatus 9 according to the first embodiment can be configured not only by hardware but also by computer software.

  In the first embodiment, the normalization processing unit 15 has been described as normalizing the signal S14 output from the BPF 14 without downsampling. However, also in the first embodiment, the normalization processing unit 15 may perform the normalization processing after downsampling as in the second embodiment.

  In the above-described embodiment, the program is described as being stored in advance in a memory or the like. However, a program for operating the tone signal detection apparatus as all or part of the entire apparatus such as the receiver 100 or executing the above-described process is stored in a flexible disk, a CD-ROM (Compact Disk Read-Only). It is stored and distributed in a computer-readable recording medium such as a memory (DVD), a digital versatile disk (MO), or a magneto optical disk (MO), and this is installed in 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.

It is a block diagram which shows the structure of the receiver which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the tone signal detection apparatus shown in FIG. It is a figure which shows the relationship between the frequency of each tone signal, the shift amount, and the frequency after a shift. It is a figure which shows the table which shows the relationship between the frequency and shift amount of a tone signal, and the center frequency of BPF connected after the normalization process part. It is a wave form diagram which shows the waveform at the time of the normalization process which a normalization process part performs. It is a figure which shows the frequency characteristic of the low frequency signal which the demodulator converted. It is a figure which shows the frequency characteristic of the signal of each part, (a) is a signal input into a frequency shift part, (b) is a frequency conversion signal which the frequency shift part converted the frequency, (c) is a frequency shift. Each frequency characteristic of the output signal of BPF connected after the part is shown. It is a block diagram which shows the structure of the tone signal detection apparatus which concerns on Embodiment 2 of this invention. It is a wave form diagram which shows the signal waveform (the 1) binarized by the normalization process part as a normalization process. It is a figure (the 1) which shows the signal waveform of each part, (a) is a signal input into a frequency shift part, (b) is a frequency conversion signal which the frequency shift part produced | generated, (c) is frequency conversion. (D) is a signal downsampled by the downsampling unit, (e) is a signal binarized by the normalization processing unit, and (f) is a signal of the normalization processing unit. Each signal waveform of the signal which BPF connected via the gain adjustment part filtered later is shown. It is a figure which shows the frequency characteristic of the signal of each part, (a) is the signal which the downsampling part downsampled, (b) is the signal which the normalization process part binarized, (c) is a normalization process Each frequency characteristic of the signal which BPF connected via the gain adjustment part after the part filtered is shown. It is a figure (the 2) which shows the signal waveform of each part, (a) is a signal input into a frequency shift part, (b) is a frequency conversion signal which the frequency shift part produced | generated, (c) is frequency conversion. (D) is a signal down-sampled by the down-sampling unit, (e) is a signal binarized by the normalization processing unit, and (f) is a signal filtered by the BPF. Each signal waveform is shown. It is a wave form diagram which shows the signal waveform (the 2) binarized by the normalization process part as a normalization process. It is a figure (the 3) which shows the signal waveform of each part, (a) is a signal input into a frequency shift part, (b) is a frequency conversion signal which the frequency shift part produced | generated, (c) is frequency conversion. (D) is a signal downsampled by the downsampling unit, (e) is a signal binarized by the normalization processing unit, and (f) is after the normalization processing unit. Each signal waveform of the signal which BPF connected via the gain adjustment part filtered is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Receiver 9 Tone signal detection apparatus 12 Frequency shift part 13 Local oscillator 15 Normalization process part 11,14,16 BPF
23 Downsampling unit

Claims (6)

A frequency signal generator that generates a frequency signal of a moving frequency that moves the frequency of the tone signal to a preset frequency band;
A frequency conversion unit that generates a frequency conversion signal by moving the frequency of the input signal including the tone signal by the moving frequency of the frequency signal generated by the frequency signal generation unit;
A normalization processing unit that normalizes the amplitude of the frequency conversion signal generated by the frequency conversion unit to generate a normalized signal;
A passband is set to the frequency band of the tone signal included in the normalized signal generated by the normalization processing unit, and a filter that filters the normalized signal;
A tone signal detection unit that detects the tone signal based on the signal filtered by the filter;
A tone signal detection apparatus characterized by the above. The normalization unit determines a reference value indicating an intensity based on the amplitude of the frequency conversion signal generated by the frequency conversion unit, and divides the frequency conversion signal by the reference value to thereby calculate the frequency conversion signal. Normalize the amplitude,
The tone signal detection apparatus according to claim 1, wherein The normalization unit normalizes the amplitude of the frequency conversion signal by adjusting and binarizing the amplitude of the frequency conversion signal generated by the frequency conversion unit,
The tone signal detection apparatus according to claim 1, wherein A downsampling unit for downsampling the frequency conversion signal generated by the frequency conversion unit;
The normalization unit normalizes the amplitude of the frequency conversion signal downsampled by the downsampling unit,
In the filter, a pass band is set to a frequency band of the tone signal included in the normalized signal.
The tone signal detection apparatus according to claim 2 or 3, Generating a frequency signal of a moving frequency that moves the frequency of the tone signal to a preset frequency band;
Generating a frequency conversion signal by moving the frequency of the input signal including the tone signal by the moving frequency of the generated frequency signal;
Normalizing the amplitude of the generated frequency conversion signal to generate a normalized signal;
Filtering the normalized signal with a filter whose passband is set to the frequency band of the tone signal included in the generated normalized signal;
Detecting the tone signal based on the signal filtered by the filter;
And a tone signal detecting method. On the computer,
A procedure for generating a frequency signal of a moving frequency for moving the frequency of the tone signal to a preset frequency band;
A step of generating a frequency conversion signal by moving the frequency of the input signal including the tone signal by the moving frequency of the generated frequency signal;
A procedure for generating a normalized signal by normalizing the amplitude of the generated frequency conversion signal,
Filtering the normalized signal with a filter whose passband is set to the frequency band of the tone signal included in the generated normalized signal;
Detecting the tone signal based on the signal filtered by the filter;
A program for running

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