JP5322671B2 - Tone detection device and wireless communication device including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a configuration for properly detecting a tone signal by achieving characteristics conventionally achieved by a lead filter or a micro-fork by digital signal processing and by achieving a narrow band which cannot be achieved by the conventional filter. <P>SOLUTION: A tone signal detecting section 31 of a DSB transmitter receiver is configured to detect a specific tone signal in an audio frequency band. The tone signal detecting section 31 is equipped with a resonator (resonant IIR filter) 5, and a tone determining section 7. An audio signal converted into a digital signal is input into the resonator 5. The tone determining section 7 determines whether or not a tone signal to be detected is included in the audio signal based on the level of the signal passing through the resonator 5. The resonator 5 is achieved by a digital signal processor (DSP). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention mainly relates to a tone detection apparatus that detects a predetermined tone signal in a voice frequency band.

  2. Description of the Related Art Conventionally, in wireless communication between ships, a specific partner communication device is called by transmitting a tone signal having a frequency corresponding to a 4-digit number unique to the communication device. This signal is generally called a selective call signal (cell call).

  A communication device having a function of detecting a selective call signal, for example, when a 4-digit number corresponding to a received tone signal matches a unique number of the own device, for example, by lighting a lamp or calling sound from a speaker. , It is to inform you that your machine has been called. Thus, the user can appropriately respond to the call without always paying attention to the received voice.

  Also known is a radio buoy (cell call buoy) that is equipped with a function for detecting a selective call signal as described above and that automatically emits radio waves in response to only a cell call call to the aircraft. Yes. This configuration is disclosed in Patent Document 1, for example.

  By the way, in the application for detecting a tone signal of a specific frequency as described above, electronic parts such as a reed filter and a microfork have been conventionally used in order to obtain a narrow band characteristic in a voice frequency band. These electronic components realize band characteristics using mechanical resonance characteristics. That is, the electric signal is converted into mechanical vibration and transmitted to a mechanical resonator, and the mechanical vibration output of the resonator is converted back into an electric signal to obtain a filter output.

JP 2008-228710 A

  However, in the configuration using the above-described lead filter or microfork, the resonance frequency is a value unique to the lead filter and microfork. Therefore, when a plurality of detectors are required, it is necessary to prepare reed filters and microforks as many as the number of detectors. Further, the bandwidth characteristics are also unique to the lead filter and the microfork. When a plurality of bandwidth characteristics are required, it is necessary to prepare as many parts as there are, which causes an increase in cost.

  Furthermore, the filter using the mechanical resonance characteristics as described above often deteriorates in a vibrating environment such as a ship, and the characteristics change due to secular change, and environmental changes such as temperature and humidity change. As a result, the characteristics may become unstable. In recent years, the production of this type of component is often discontinued, and the acquisition itself is not easy. On the other hand, if a normal band pass filter is used, it is very difficult to obtain a steep selectivity due to the influence of the time delay.

  The present invention has been made in view of the above circumstances. The purpose of the present invention is to realize characteristics that were conventionally realized by a lead filter and a microfork by digital signal processing, and to achieve a narrow band that is impossible with a conventional filter. It is intended to provide a configuration capable of accurately detecting a tone signal.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

According to an aspect of the present invention, the following configuration is provided in a tone detection apparatus capable of detecting a specific tone signal in a voice frequency band. That is, the tone detection apparatus includes a resonance type IIR filter, a determination unit, a first amplitude detection unit, and a first average value calculation unit . The resonance type IIR filter receives an audio signal converted into a digital signal. The determination unit determines whether a tone signal to be detected is included in the audio signal based on a level of a signal that has passed through the resonance type IIR filter. The first amplitude detector detects an amplitude of a signal that does not pass through the resonance type IIR filter. The first average value calculation unit calculates an average value of amplitudes detected by the first amplitude detection unit. A plurality of the resonance type IIR filters are provided, and the respective resonance frequencies are different from each other. The determination unit is provided corresponding to the resonance type IIR filter, and the average value calculated by the first average value calculation unit is output to each determination unit. Each determination unit includes a second amplitude detection unit, a second average value calculation unit, and a magnification calculation unit. The second amplitude detector detects the amplitude of the signal that has passed through the resonant IIR filter. The second average value calculation unit calculates an average value of amplitudes detected by the second amplitude detection unit. The magnification calculator calculates a signal level magnification by dividing the average value calculated by the second average value calculator by the average value calculated by the first average value calculator. The audio signal converted into a digital signal is input in parallel to a plurality of resonant IIR filters. When the waveform of the tone signal to be detected is input to a plurality of the resonance type IIR filters, only the waveform passing through one of them has a large amplitude.

As a result, a steep selectivity characteristic can be obtained with the IIR resonance filter, and a narrow band that cannot be achieved with the conventional filter can be realized. In addition, since the tone signal is detected using a digital filter, there is no problem that the characteristics become unstable due to aging or environmental changes, and it is easy to cope with the required characteristics. Further, it is possible to realize a simple configuration capable of identifying tone signals having different frequencies.

In the tone detection device, the resonant IIR filter is preferably realized by a digital signal processing device , and each of the determination units preferably includes a comparison unit that compares the magnification calculated by the magnification calculation unit with a threshold value. .

  As a result, the filter can be realized as a program. Therefore, even if a plurality of filters are configured, the circuit scale can be made the same as that of one filter. In addition, the specification can be changed easily by changing the program.

  In the tone detection apparatus, it is preferable that an offset remaining in the waveform in the resonance type IIR filter is removed before an audio signal is input to the resonance type IIR filter in order to detect a next tone signal. .

  Accordingly, when tone signals having different frequencies are continuously input, the next tone signal can be detected after setting the offset remaining in the waveform of the resonance type IIR filter to zero. As a result, the detection capability can be improved and a malfunction can be avoided.

  According to another aspect of the present invention, a wireless communication device including the above-described tone detection device is provided.

The perspective view which showed the whole structure of the DSB transmitter / receiver which concerns on one Embodiment of this invention. The functional block diagram of a DSB transceiver. The block diagram which shows the structure of a tone signal detection part. The block diagram which shows the structure of a resonator. The block diagram which shows the structure of a signal level detection part and a tone determination part. The graph explaining the offset part contained in an input waveform.

  Next, embodiments of the invention will be described. FIG. 1 is a perspective view showing an overall configuration of a DSB transceiver 1 according to an embodiment of the present invention. FIG. 2 is a functional block diagram of the DSB transceiver 1.

  The DSB transceiver (wireless communication device) 1 of the present embodiment shown in FIG. 1 can transmit and receive audio using amplitude modulated waves called double side bands (DSB). The DSB transceiver 1 can be used to communicate with fellow ships when, for example, fishing boats operate in a fleet.

  As shown in FIG. 2, the DSB transceiver 1 includes a transceiver body 10 to which a microphone 14, a speaker 16, and an antenna 17 can be connected. The transmitter / receiver body 10 incorporates a transmitter 20 and a receiver 21 for exchanging voice by wireless communication. Further, the transceiver body 10 is provided with a control unit 19 including a digital signal processing device (DSP) for controlling the transmission unit 20, the reception unit 21, and the like.

  As shown in FIG. 1, the microphone 14 includes a changeover switch 15 for switching between transmission and reception. This change-over switch 15 is sometimes referred to as a PTT switch, taking the acronym of Push To Talk, meaning that it is switched to the transmission side when pressed.

  The changeover switch 15 is electrically connected to the transmission / reception switching unit 23 shown in FIG. As the antenna 17, an appropriate one can be used, for example, a known whip antenna.

  As shown in FIG. 1, a flat panel is provided on the front side of the transceiver body 10. A display unit 11 and an operation unit 12 are arranged on this panel. The display unit 11 and the operation unit 12 are electrically connected to the control unit 19 shown in FIG.

  The display unit 11 is configured as a liquid crystal display, for example, and can display information related to the operating status of the DSB transceiver 1 for confirmation. For example, the information includes a channel currently used for communication, a radio wave reception level, and the like. The display unit 11 is configured to be able to display various setting items, various operation items, and the like related to the transmitter / receiver main body 10 with a menu, and an operation related to the menu can be performed by using an operation unit 12 described later.

  The operation unit 12 includes various operation tools such as operation buttons and a rotary dial. The user can give the DSB transceiver 1 (control unit 19) a desired instruction such as switching the sensitivity of the reception unit 21 by performing an appropriate operation.

  The transmission unit 20 can send out an audio signal on a predetermined channel (frequency) by modulating a high-frequency signal based on the audio signal input from the microphone 14, amplifying the signal, and outputting the amplified signal to the antenna 17. The receiving unit 21 can perform processing such as amplification and demodulation on the signal input from the antenna 17, extract an audio signal transmitted through a predetermined channel (frequency), and output the audio signal to the speaker 16. As described above, the exchange of audio signals by so-called A3E radio waves is realized.

  The tone signal generator 30 generates a predetermined tone signal in the audio frequency domain and outputs it to the transmitter 20. The tone signal may be a selective call signal (cell call) for selecting and calling a specific ship, a caution signal for notifying surrounding ships when an emergency situation occurs.

  The tone signal generator 30 includes an unillustrated oscillator that generates a sine wave. For example, when transmitting the selective call signal, the user instructs a four-digit number (selective call number) for specifying the communication apparatus of the other party by operating the operation unit 12. Then, for each digit, a tone frequency of about 0.5 to 2 kHz corresponding to the numbers 1, 2,..., 0 is generated in the tone signal generation unit 30, and four tone signals are transmitted via the transmission unit 20. Are transmitted continuously from the antenna 17.

  The tone signal detection unit (tone detection device) 31 monitors the audio signal demodulated by the reception unit 21, and when detecting a predetermined tone signal (specifically, the cell call signal), the control unit 19 It is configured to send a signal. When the four-digit number (selective call number) corresponding to the four tone frequencies matches the unique number of the own device, the control unit 19 displays an appropriate display on the display unit 11, The user is notified by an appropriate method such as turning on a lamp provided on the panel 10 or outputting a ringing tone from the speaker 16. Thereby, the user can know that the ship is called by a cell call.

  Next, a detailed configuration of the tone signal detection unit 31 provided in the DSB transceiver 1 will be described. FIG. 3 is a block diagram illustrating a configuration of the tone signal detection unit 31.

  The tone signal detection unit 31 shown in FIG. 3 includes an A / D converter 4, a resonator 5 as a bandpass filter, a signal level detection unit 6, and a tone determination unit 7 as main components. .

  The demodulated audio signal from the receiving unit 21 is converted into digital data through the A / D converter 4 and then input in parallel to the plurality of resonators 5 and simultaneously passes through the resonators 5. Each resonator 5 is configured as a resonance type IIR filter, a total of 11 pieces corresponding to 10 numbers “1”, “2”,... “0” and “R”. The resonator 5 is arranged.

  In each resonator 5, a predetermined frequency predetermined by the radio equipment rule corresponding to each number is set as a resonance frequency. “R” means repetition of the immediately preceding number in the cell call. For example, a four-digit number “0011” is expressed as “0R1R”, and a tone signal corresponding to this is exchanged between the communication devices.

  A tone determination unit (determination unit) 7 is provided corresponding to each resonator 5. The output signal of the resonator 5 is input to the tone determination unit 7 and the presence / absence of a tone signal corresponding to the resonator 5 is determined. When it is determined that there is a tone signal, a tone detection signal is transmitted to the control unit 19.

FIG. 4 is a block diagram showing the configuration of one resonator 5. The resonator 5 is configured as a known IIR resonance type filter including a multiplier, an adder, and a unit delay element, whereby a steep selectivity characteristic can be obtained. When the resonance frequency of the resonator 5 is F and the resonance bandwidth is B, the coefficients a ₁ , a _2, and b ₀ shown in FIG. 4 can be expressed by the following equations (1) to (3). .

  The resonator 5 (resonance type IIR filter, bandpass filter) described above is not composed of a special part, and the digital signal processing device (DSP) provided in the DSB transceiver 1 can perform digital signal processing by a program. It is realized. Therefore, functions can be easily added without changing hardware by newly adding a program to a DSP circuit that has been provided for the purpose of performing normal communication control, display control of the display unit, and the like. Can do. In the present embodiment, the signal level detection unit 6 and the tone determination unit 7 are also implemented programmatically in the DSP.

  Further, since the filter is configured using digital processing, it is easy to satisfy required characteristics (that is, frequency and bandwidth). In the present embodiment, since a steep selectivity characteristic is obtained by the IIR resonance type filter, a narrow band (for example, 500 ± 1. 5 Hz) can be realized.

  Furthermore, since the resonator 5 is configured as a digital filter in this way, the influence of secular change can be avoided and the environment such as temperature, humidity, and vibration can be avoided as compared with the filter using the mechanical resonance characteristic described above. The characteristics can be stabilized regardless of the change of.

  The signal level detection unit 6 shown in FIG. 3 is configured to generate and output a reference signal for determining the presence or absence of a tone signal in each tone determination unit 7. Specifically, as shown in FIG. 5, the signal level detection unit 6 includes an amplitude detection unit 61 and an average value calculation unit 62.

  The amplitude detector 61 detects the amplitude of the demodulated audio signal obtained from the receiver 21. The average value calculation unit 62 calculates the average value of the amplitude detected continuously and outputs the result to the tone determination unit 7.

  The tone determination unit 7 includes an amplitude detection unit 71, an average value calculation unit 72, a magnification calculation unit 73, and a comparison unit 74.

  The amplitude detector 71 is configured similarly to the amplitude detector 61 of the signal level detector 6 and detects the amplitude of the signal that has passed through the resonator 5. The average value calculator 72 calculates the average value of the amplitude detected by the amplitude detector 71. The magnification calculation unit 73 divides the calculation result of the average value calculation unit 72 by the calculation result of the average value calculation unit 62 to calculate the signal level magnification.

  This signal level magnification (level ratio) indicates how many times the level of the signal that has passed through the resonator 5 is that of the signal that has not passed. Here, if a tone signal that matches the resonance frequency of the resonator 5 is included in the demodulated audio signal, the tone signal component is emphasized by the resonator 5 by several tens of times, for example. The magnification of is significantly increased. In the present embodiment, this is utilized to compare the magnification calculated by the magnification calculation unit 73 with a predetermined threshold by the comparison unit 74, and when it exceeds this threshold, it is determined that there is a tone signal.

  The design parameters of the resonator 5 (bandpass filter) and the tone determination unit 7 include a filter coefficient, a Q value, a threshold value, and a delay amount, which are appropriately determined according to circumstances. For example, if the threshold value is set high, it approaches the spire value of the resonance frequency, so that the bandwidth can be set narrow. On the other hand, if the threshold value is set low, it becomes close to the base of the resonance frequency, so that the band can be set wide. In this way, by appropriately setting the threshold value, it is possible to obtain band characteristics that match the purpose of use.

  In the case of a cell call, tone signals having frequencies corresponding to four numbers are continuously input. Accordingly, at the timing when the tone determination unit 7 detects the first number frequency in the above configuration, the tone signal having the frequency corresponding to the next other number starts to be input to all the resonators 5. At this time, if the offset of the input waveform of the previous number (shown in FIG. 6) remains in the resonator 5, the frequency at which the next input waveform reaches the threshold value is lowered, and the frequency (ie, the number) is accurately set. Cannot be detected.

  Details will be described below. The hatched portion in FIG. 6 indicates a waveform offset that becomes a problem when a tone signal corresponding to “2” is input after a tone signal corresponding to “1” is input. In the case of a cell call, the frequency corresponding to the number is determined in increments of 30 Hz such as 502.5 Hz, 532.5 Hz,... In the order of “1” to “0”, “R”, and the last “R”. The frequency corresponding to is 802.5 Hz. When a tone signal of “1” is input, a mountain-shaped waveform having a peak at 502.5 Hz is input to all the resonators 5 of “1” to “R”. Only the waveform that has passed through the resonator 5 of “1” has a large amplitude, and it is determined that the tone signal is “1”.

  Then, immediately after that, a signal having a frequency lower than the range to be detected as “2” is input for some reason. Since such a signal does not fall within the resonance bandwidth of the resonator 5 whose peak portion is “2”, the tone determination unit 7 of “2” normally does not detect an amplitude exceeding the threshold, and this signal is “ It is not determined that the signal is “2”. However, immediately after the “1” tone signal is input, the waveform of the “1” tone signal remains in the resonator 5 of “2” to a certain extent. Therefore, in the resonator 5 of “2”, the newly input signal waveform of the problem is added to the remaining portion of the tone signal waveform of “1”. As a result, the tone determination unit 7 detects the signal waveform. The amplitude may exceed a threshold value. This means that a signal that should not be detected as “2” is erroneously detected as a tone signal of “2”.

  Thus, if a past input waveform remains, the remaining portion remains as an offset in the waveform to be determined at present, causing malfunction. Such an offset is a greater problem when the frequencies of the two numbers are close, such as “1” and “2” above, but when they are some distance apart, such as “1” and “3”. However, as long as there is a portion where the signal waveforms overlap as shown in FIG.

  In this regard, in the present embodiment, the control unit 19 sends a reset signal to all tone determination units 7 at a predetermined timing corresponding to the interval between the signals of each digit, and each tone determination unit 7 that has received this signal receives the reset signal. By resetting the resonator 5, the offset remaining in the waveform is returned to zero. Therefore, when the next number is detected using the resonator 5, the influence of the residual offset caused by the past input waveform can be eliminated, so that the tone detection capability can be improved satisfactorily.

  As described above, the tone signal detection unit 31 included in the DSB transceiver 1 of the present embodiment is configured to be able to detect a specific tone signal in the audio frequency band. The tone signal detection unit 31 includes a resonator 5 as a resonance type IIR filter and a tone determination unit 7. An audio signal converted into a digital signal is input to the resonator 5. The tone determination unit 7 determines whether or not a tone signal to be detected is included in the audio signal based on the level of the signal that has passed through the resonator 5.

  Thereby, a steep selectivity characteristic can be obtained by the resonator 5 as a resonance type IIR filter, and a narrow band that cannot be achieved by a conventional filter can be realized. In addition, since the tone signal is detected using a digital filter, the characteristics do not become unstable due to aging and environmental changes, and it is easy to cope with the required characteristics.

  In the present embodiment, it is preferable that the resonator 5 of the tone signal detection unit 31 is realized by a digital signal processing device.

  Thereby, since the filter such as the resonator 5 can be realized as a program, even if a plurality of filters are configured, the circuit scale can be configured in the same manner as one filter. In addition, the specification can be changed easily by changing the program.

  In the present embodiment, a plurality of resonators 5 are provided, and the respective resonance frequencies are different from each other. The audio signal converted into a digital signal is input to the plurality of resonators 5 in parallel.

  As a result, a simple configuration capable of identifying tone signals having different frequencies can be realized.

  Further, in the present embodiment, before the audio signal is input to the resonator 5 in order to detect the next tone signal, the offset remaining in the waveform in the resonator 5 is removed.

  As a result, when tone signals of different frequencies are input continuously, the detection capability can be improved and malfunctions can be avoided by detecting the next tone signal after setting the offset remaining in the waveform to zero. it can.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  The configuration of the resonator 5 is not limited to that shown in FIG. 4, and various other configurations of resonators may be employed.

  The receiving unit 21 may be omitted from the DSB transceiver 1 of the above-described embodiment, and the DSB transmitter (that is, a wireless communication device dedicated to transmission) may be configured.

  The configuration of the above embodiment is not limited to the voice communication device using the DSB. For example, various voice communication devices such as an SSB transmitter / receiver using a single sideband (SSB), an FM transmitter / receiver performing frequency modulation, and the like. Can be applied to.

  The tone detection configuration described above is not limited to the reception of the selective call signal, and can be used for receiving a caution signal, for example. Further, not only the wireless communication device but also the above tone detection device can be used for tone detection in an answering machine, a remote control or the like.

  In the above embodiment, the control unit 19 transmits a signal for resetting the resonator 5 to the tone determination unit 7, but the control unit 19 directly transmits a reset signal to the resonator 5 to reset the resonator 5. It can also be changed to a configuration.

  In the above embodiment, regardless of whether or not the tone determination unit 7 determines that the tone signal has been detected from the audio signal, the resonator 5 is reset at an appropriate timing, and the offset due to past signal input is calculated. It is configured to return to zero. However, it can be changed so that the reset signal is transmitted from the control unit 19 only when the tone determination unit 7 determines that the tone signal to be detected is included in the audio signal.

  In the above-described embodiment, in order to remove the influence of the offset, all the resonators 5 are reset before the next input starts. However, for the resonator 5 that is determined not to be reset, such as when the frequency of the immediately preceding input signal and the resonance frequency of the resonator 5 are significantly different, the reset may be omitted.

1 DSB transceiver (wireless communication device)
5 Resonator (Resonant IIR filter)
7 Tone determination unit 19 Control unit 31 Tone signal detection unit (tone detection device)

Claims (4)

In a tone detector capable of detecting a specific tone signal in a voice frequency band,
A resonant IIR filter to which an audio signal converted into a digital signal is input;
A determination unit that determines whether or not a tone signal to be detected is included in the audio signal based on a level of a signal that has passed through the resonant IIR filter;
A first amplitude detector that detects the amplitude of a signal that does not pass through the resonant IIR filter;
A first average value calculation unit for calculating an average value of amplitudes detected by the first amplitude detection unit;
With
A plurality of the resonance type IIR filters are provided, and the respective resonance frequencies are different from each other.
The determination unit is provided corresponding to the resonance type IIR filter, and the average value calculated by the first average value calculation unit is output to each determination unit,
Each of the determination units includes a second amplitude detection unit that detects an amplitude of a signal that has passed through the resonant IIR filter, and a second average value calculation unit that calculates an average value of the amplitudes detected by the second amplitude detection unit. And a magnification calculator that calculates a signal level magnification by dividing the average value calculated by the second average value calculator by the average value calculated by the first average value calculator,
The audio signal converted into a digital signal is input in parallel to a plurality of resonant IIR filters,
When the waveform to be detected the tone signal is input to the plurality of the resonant IIR filter, tone detection which only waveform input to the determination unit through one is characterized by having a large amplitude apparatus. The tone detection device according to claim 1,
The resonant IIR filter is realized by a digital signal processing device ,
Each of the determination units includes a comparison unit that compares the magnification calculated by the magnification calculation unit with a threshold value . The tone detection device according to claim 1 or 2,
A tone detection apparatus, wherein an offset remaining in a waveform in the resonance type IIR filter is removed before an audio signal is input to the resonance type IIR filter in order to detect a next tone signal.   A wireless communication device comprising the tone detection device according to any one of claims 1 to 3.

Images