JP4117109B2 - Receiving machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiver, and more particularly to a receiver having a decompression circuit.
[0002]
[Prior art]
In order to reduce noise in the transmission system, a compander system that compresses an audio signal on the transmitter, for example, a wireless microphone side, modulates and transmits the signal, demodulates it on the receiver side, and then decompresses it is used. is there. An example of a receiver used in this system is shown in FIG. In the figure, a radio wave from a wireless microphone is received by a receiving unit (not shown) and converted into an intermediate frequency signal. This intermediate frequency signal is supplied to the detection circuit 2 to generate a detection signal. This detection signal is supplied to a decompression circuit, for example, an expander 4, where it is decompressed and output as an audio output. In this receiver, in order to reduce residual noise when there is no radio wave from the wireless microphone, a voice switch 6 is provided on the input side of the expander 4, and a noise squelch detection circuit 8 and tone squelch detection are used to control the opening and closing of the switch. A circuit 10 and a CPU 12 are provided.
[0003]
That is, when transmission from the wireless microphone is started as shown in FIG. 5A, the noise becomes a predetermined level or less, and the noise squelch circuit 8 sends the detection signal to the CPU 12 as shown in FIG. 5B. Supply. Further, the tone squelch detection circuit detects that the tone signal transmitted from the wireless microphone is included in the detection output signal as shown in FIG. 5C, and supplies this detection signal to the CPU 12. When both detection signals are supplied, the CPU 12 closes the voice switch 6 as shown in FIG. 4D and supplies the detection signal to the expander 4, and the expander 4 expands the same to detect the same. Output as shown in FIG.
[0004]
[Problems to be solved by the invention]
However, the expander 4 requires a rise time after the detection signal is input until it can be stably expanded. In the receiver described above, the detection signal is supplied to the expander 4 only when both the squelch detection circuits 8 and 10 detect the detection signal. Therefore, there is a problem that the rising characteristic of the sound output from the expander 4 becomes dull. That is, when the voice switch 6 is closed and the voice is immediately amplified, the rise of the expander 4 and the voice are overlapped, and the voice is heard as a crisp sound. In particular, the crispness is conspicuous when a single sound such as a chime sound is amplified simultaneously with the start of transmission of the wireless microphone.
[0005]
An object of the present invention is to improve the crispness of an audio signal output from a decompression circuit even when the decompression circuit is used.
[0006]
[Means for Solving the Problems]
The present invention includes receiving means for receiving a transmission signal modulated with a compressed audio signal. The detection means detects the output signal of the reception means, and generates a detection signal. A detection signal is input to the expansion means and is expanded. However, a rise time is required after the detection signal is input until the expansion means outputs a stable output signal. First switching means is provided between the detection means and the input side of the expansion means. The first switching means is switched between a signal supply state in which the detection signal is supplied to the expansion means and a signal non-supply state in which the detection signal is not supplied to the expansion means. Second switching means is provided on the output side of the expansion means. The second switching means is switched between an output state in which the output signal of the expansion means is output and a non-output state in which the output of the output signal of the expansion means is stopped. A noise squelch means generates a detection signal when the detection signal is supplied and the noise contained therein is lower than a predetermined level. When the detection signal of the noise squelch means of non-input, the first switching means to the signal non-supply state, the second switching means and the non-output state, when the detection signal of said noise squelch means is inputted , the first switching means and said signal supply state, from the detection signal is input, the control means of the second switching means and the output state is provided after the elapse of the rise time. In the case of converting the transmission signal into an intermediate frequency signal, the receiving means detects the level of the intermediate frequency signal in place of the noise squelch means, and generates a detection signal when this level exceeds a predetermined level. Means can be used.
[0008]
As the squelch detection means, a noise squelch detection means can be used. The noise squelch detecting means has a fast response, can quickly bring the first switching means into the signal supply state, and can speed up the operation of the expansion means.
[0009]
Further, the control means can include a tone squelch detection means for detecting a tone signal included in the detection signal. The control means sets the second switching means to the output state when this tone signal is detected.
[0010]
When configured in this way, the tone squelch circuit is slower in response than the noise squelch detection circuit. Therefore, if the second switching means is switched by the tone squelch circuit, the output signal of the expansion means can be output via the second switching means after the rise time of the expansion means has elapsed. In particular, since the tone squelch detection circuit is generally used for such a receiver, it is possible to output a crisp sound without increasing the cost.
[0011]
Alternatively, the control means can include delay means for delaying the noise squelch detection signal. In this case, the control means sets the second switching means to the output state by the output signal of the delay means.
[0012]
In such a configuration, the delay time can be arbitrarily adjusted, so that the delay time can be set to an optimum time corresponding to the rising characteristic of the expansion means, and the responsiveness can be improved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The receiver according to the first embodiment of the present invention has detection means, for example, a detection circuit 20, as shown in FIG. The detection circuit 20 is supplied with an intermediate frequency signal from a receiving means (not shown) such as a tuner unit. The tuner unit receives a modulated high-frequency signal from a transmitter (not shown), for example, a wireless microphone, converts this to an intermediate frequency signal, and supplies the intermediate-frequency signal to the detection circuit 20. The detection circuit 20 detects this and generates a detection signal. In the wireless microphone, an audio signal collected by the microphone is compressed, thereby modulating and transmitting a high-frequency signal having a predetermined frequency.
[0014]
The detection signal of the detection circuit 20 is supplied to the input side of the expansion means, for example, the expander 24 via the first switching means, for example, the voice switch 22. That is, the audio switch 22 is connected in series between the output side of the detection circuit 20 and the input side of the expander 24. The voice switch 22 is controlled by the CPU 28 of the control means 26. That is, the voice switch 22 is selected by the CPU 28 to one of a signal supply state, for example, an on state, and a signal non-supply state, for example, an off state.
[0015]
Further, on the output side of the expander 24, second switching means, for example, a voice switch 30 is provided. The voice switch 30 is also selected by the CPU 28 from a signal output state, for example, an on state or a signal non-output state, for example, an off state. Note that the output of the audio switch 30 is amplified, for example, and then supplied to the speaker system.
[0016]
The detection signal of the detection circuit 20 is supplied to squelch detection means, for example, a noise squelch detection circuit 32. Although not shown, the noise squelch detection circuit 32 has a filter for detecting a noise component, and generates a detection signal when the level of the output signal of the filter is lower than a predetermined level. This detection signal is supplied to the CPU 28. The CPU 28 turns on the voice switch 22 when receiving this detection signal, and turns off the voice switch 22 when this detection signal disappears.
[0017]
The control circuit 28 has a tone squelch detection circuit 34. The tone squelch detection circuit 34 generates a detection signal when it detects a tone signal included in the detection signal. This tone signal is transmitted from the wireless microphone together with the audio signal collected by the microphone of the wireless microphone. This detection signal is supplied to the CPU 28. When the detection signal is supplied from the tone squelch detection circuit 34 while the detection signal from the noise squelch detection circuit 32 is supplied, the CPU 28 turns on the voice switch 30.
[0018]
Next, the operation of this receiver will be described. In a state where transmission from the wireless microphone is not performed, both the voice switches 22 and 30 are in an off state. When transmission is started from the wireless microphone as shown in FIG. 2A, the noise squelch detection circuit 32 generates a detection signal as shown in FIG. As shown in (c), the CPU 28 turns on the voice switch 22. As a result, a detection signal is supplied to the expander 24 as shown in FIG. At this time, the output of the expander 24 is affected by the rise characteristic, and the output is crisp, but the voice switch 30 is off, so that the output signal of the crisp expander 24 is transmitted via the voice switch 30. Is not output.
[0019]
Eventually, the tone squelch detection circuit 34 detects the tone signal and supplies it to the CPU 26 as shown in FIG. Since the detection signal is supplied from both the noise squelch detection circuit 32 and the tone squelch detection circuit 34, the CPU 26 turns on the voice switch 30 as shown in FIG. 5F, and as shown in FIG. The output signal of the expander 24 is output.
[0020]
The time from when the noise squelch detection circuit 32 generates the detection signal to when the tone squelch detection circuit 34 generates the detection signal is several hundred milliseconds. On the other hand, the rise time of the expander 24 (the time from when the supply of the detection signal is disclosed until a stable output signal can be output) is several tens of milliseconds. Accordingly, the output of the expander 24 is stable several tens of milliseconds after the voice switch 22 is turned on, and the voice switch 30 is turned on after a sufficient time has elapsed, so that the rise of the voice switch 22 is slow. An audio signal with improved is output from the audio switch 30.
[0021]
A receiver according to the second embodiment is shown in FIG. In addition, the same code | symbol is attached | subjected to the part equivalent to 1st Embodiment, and the description is abbreviate | omitted. In this embodiment, a delay circuit 36 is provided in the control circuit 26a in place of the tone squelch detection circuit 34. The detection signal of the noise squelch detection circuit 32 is supplied to the delay circuit 36. The delay circuit 36 delays this for a predetermined time and then supplies it to the CPU 28. When the delay signal from the delay circuit 36 is supplied, the CPU 28 turns on the voice switch 30.
[0022]
In this receiver as well as the receiver of the first embodiment, after the voice switch 22 is turned on, the voice switch 30 can be turned on after the delay time has elapsed, and when the delay time is appropriately set, An audio signal with improved rise can be output from the audio switch 30. Moreover, since the delay circuit 36 is used, the output of the audio signal from the audio switch 30 can be performed at an optimal timing. When the noise squelch detection circuit 32 generates the detection signal, the expander 22 generates a stable output signal several tens of milliseconds after the detection signal is supplied to the expander 22. Therefore, when the delay time of the delay circuit 36 is set to a time slightly slower than, for example, several tens of milliseconds, when the output signal of the expander 22 is stabilized, a stable audio signal can be immediately output from the expander 22. It is not necessary to wait for several hundred milliseconds as in the first embodiment, and the responsiveness can be improved.
[0023]
In the above two embodiments, the present invention is implemented in the receiver for the wireless microphone. However, the present invention can also be implemented in a receiver for receiving radio waves from other transmitters. In both of the above-described embodiments, the noise squelch circuit is used. For example, the level of the intermediate frequency signal of the tuner unit is detected and compared with a reference value. It is also possible to use a carrier squelch detection circuit that generates In both of the above embodiments, the audio switch 24 is connected in series between the detection circuit 20 and the expander 22. However, the detection circuit 20 and the expander 22 are directly coupled, and the audio switch 22 is connected. You may connect between the input side of the panda 24 and a reference potential point. In this case, the audio switch 22 is turned off in the signal supply state, and the audio switch is turned on in the signal non-supply state. Similarly, the audio switch 30 may be connected between the output side of the expander 22 and a reference potential point. In this case, the voice switch 30 is turned off in the signal output state, and the voice switch 30 is turned on in the signal non-output state.
[0024]
【The invention's effect】
As described above, according to the present invention, the switching means between the input side and the output side of the expansion means is provided, and the rise time of the expansion means has elapsed since the detection signal was supplied via the switching means on the input side. Later, since the output signal of the expansion means is output via the output-side switching means, the transmission system noise is reduced by providing the expansion means, and the residual noise by providing the input-side switching means. The rise of the audio signal output from the decompression means can be improved while maintaining the respective reductions.
[Brief description of the drawings]
FIG. 1 is a block diagram of a receiver according to a first embodiment of this invention.
FIG. 2 is a waveform diagram of each part of the receiver of FIG. 1;
FIG. 3 is a block diagram of a receiver according to a second embodiment of this invention.
FIG. 4 is a block diagram of a conventional receiver.
FIG. 5 is a waveform diagram of each part of the receiver of FIG. 4;
[Explanation of symbols]
20 Detection circuit (Detection means)
22 Voice switch (first switching means)
24 Expander (extension means)
26 Control circuit (control means)
32 Noise squelch detection circuit (squelch detection means)

Claims (4)

Receiving means for receiving a transmission signal modulated with a compressed audio signal;
Detection means for detecting the output signal of the reception means and generating a detection signal;
The detection signal is input and is expanded, and expansion means that requires a rise time until the stable output signal is output after the detection signal is input ;
Provided between the detection means and the input side of the decompression means, and the detection signal is supplied to the decompression means, and the detection signal is not supplied to the decompression means. First switching means to be switched;
A second switching means provided on the output side of the decompression means, which is switched between an output state for outputting an output signal of the decompression means and a non-output state for stopping the output of the output signal of the decompression means;
Noise squelch means for generating a detection signal when the detection signal is supplied and noise contained therein is smaller than a predetermined level ;
When a detection signal of the noise squelch means of non-input, the first switching means to the signal non-supply state, the second switching means and the non-output state, when the detection signal of said noise squelch means is inputted A control means for setting the first switching means to the signal supply state and setting the second switching means to the output state after elapse of the rising time after the detection signal is input;
Receiving receiver. 2. The receiver according to claim 1 , wherein the control means includes tone squelch means for detecting a tone signal included in the detection signal, and when the tone signal is detected by the tone squelch means, the second switching means is changed to the second squelch means. Receiver that is in the output state. 2. The receiver according to claim 1 , wherein the control means includes delay means for delaying a detection signal of the noise squelch means to be equal to or longer than the rise time , and the second switching means is set in the output state by an output signal of the delay means. And receiver. Receiving means for receiving a transmission signal modulated with a compressed audio signal and converting it to an intermediate frequency signal;
Detection means for detecting the intermediate frequency signal from the reception means and generating a detection signal;
The detection signal is input and expanded, but the expansion means requires a rise time until a stable output signal is output; and
Provided between the detection means and the input side of the decompression means, and the detection signal is supplied to the decompression means, and the detection signal is not supplied to the decompression means. First switching means to be switched;
A second switching means provided on the output side of the decompression means, which is switched between an output state for outputting an output signal of the decompression means and a non-output state for stopping the output of the output signal of the decompression means;
A carrier squelch means for detecting a level of the intermediate frequency signal and generating a detection signal when the level is equal to or higher than a predetermined level;
When the detection signal of the carrier squelch means is input when the detection signal of the carrier squelch means is not input, the first switching means is set to the signal non-supply state, the second switch means is set to the non-output state. A control means for setting the first switching means to the signal supply state and setting the second switching means to the output state after elapse of the rising time after the detection signal is input;
Receiving receiver .

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