JPH07202733A - Wireless receiver - Google Patents

Abstract

PURPOSE:To set squelch level of a receiver automatically in the wireless equipment used in an area with a limited space like in a room. CONSTITUTION:The wireless receiver is provided with a noise detection circuit 23 detecting only a noise component of a prescribed frequency or over included in an audible frequency signal outputted from a detection circuit 11, an integration circuit 25 integrating the noise detection output by a prescribed time constant to generate an integration output, a minimum value storage circuit 29 storing a minimum integration output when a transmitter being a radio wave generating source moves within its existing area, an adder circuit 31 subtracting a prescribed value from the minimum value from the minimum value, and a comparator circuit 35 outputting a control signal to close a switch section 15 of a squelch circuit 37 when a noise detection output is the output of the adder circuit 31 or over, and an audio frequency signal is outputted from an output terminal 39 by closing the switch section 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, wireless
A receiver of a wireless device used in a limited area such as a room such as a wireless receiver for a microphone device (hereinafter referred to as a receiver), and particularly, to automatically adjust a squelch level. The present invention relates to a receiver having a squelch circuit that can perform

[0002]

2. Description of the Related Art Generally, a receiver of a wireless device is used when the transmitter stops transmitting radio waves or when the radio waves transmitted by the transmitter are difficult to reach the receiver due to some influence on the transmission path. , A squelch (muting) circuit is provided in order to remove noise that is unpleasant to the ear generated from the receiver. Further, this squelch circuit is also used to reduce the influence of interference radio waves from the outside.

This squelch circuit is classified into a noise squelch system in which a signal path is opened and closed according to a noise level other than audio frequencies, and a carrier wave squelch system in which a signal path is opened and closed according to a carrier level. In either method, the noise level or the carrier level is compared with the squelch level, and the switch section of the squelch circuit is opened / closed based on the comparison result, thereby opening / closing the signal path of the receiver.

Conventionally, a receiver having a function of varying the squelch level has, for example, a squelch level adjusting knob or the like in the receiver, and the squelch level is manually adjusted by operating the squelch level. Was.

The adjustment of the squelch level normally does not output noise from the receiver when no radio wave is transmitted from the transmitter, that is, when there is no received signal from the receiver (hereinafter referred to as "no signal"). It is adjusted to the level of degree. When there is an interfering radio wave from the outside when there is no signal, the squelch level is raised until the receiver receives the interfering radio wave and does not output noise.

In this way, by adjusting the squelch level, the required S / N ratio suitable for the radio wave condition and the use condition of the transmitter / receiver can be obtained, thereby eliminating the noise of the receiver which is uncomfortable to hear. be able to. In addition, it is possible to reduce the influence of external interference waves, and as a result, it is possible to reduce interference with radio waves of other wireless devices, such as co-channel interference, adjacent channel interference, and intermodulation interference.

[0007]

However, by increasing the squelch level, the S / N ratio of the receiver is improved, which makes it less susceptible to external noise such as jamming radio waves. The reach of radio waves between transmitters and receivers becomes shorter. Therefore, if the squelch level is raised more than necessary, the reach of radio waves between the transmitter and the receiver will be extremely short, which will reduce the transmittable and receivable range of the transceiver, that is, the usable range.

For example, if the receiver is for a wireless microphone device, the wireless microphone device is used in a limited area, such as a conference room, and the receiver is used in this area. Are fixed in place, while microphones are used in places away from the receiver, fixed or moving in an area. Therefore, by raising the squelch level more than necessary,
The usable range between the microphone and receiver becomes extremely small, which allows the receiver to receive the radio waves transmitted by the microphone within the area where this wireless microphone device is used (hereinafter referred to as the "use area"). There is a problem that some areas will be lost.

In order to prevent this problem, conventionally, when adjusting the squelch level of a wireless microphone device, one person holds a microphone and moves throughout the area of use, while another person receives the receiver. The squelch level was adjusted while monitoring the reception status of the radio waves transmitted from the moving microphone. However, as mentioned above, in order to carry out this adjustment method, two people, a person who moves with a microphone and a person who adjusts the squelch level at the receiver side, are required, and it is not possible for one person to make adjustments. There was a problem.

Further, due to the squelch level adjusted by the above procedure, there is no area in the use area where the receiver cannot receive the radio wave transmitted by the microphone, and the electric field strength of the radio wave generated by carrying the microphone around. In order to confirm that the squelch level has an appropriate margin so that the squelch circuit will not operate frequently due to a slight change in the strength of the radio wave, the squelch level of the above procedure will be checked. It is necessary to repeat the adjustment several times, which is very troublesome.

The above-mentioned problem is not limited to the wireless microphone device, but is a problem relating to receivers of all wireless devices used in a limited area such as an indoor space. An object of the present invention is to provide a receiver capable of automatically setting a squelch level in order to solve these problems.

[0012]

The receiver of the first invention comprises:
A frequency conversion unit that mixes a received signal input from the antenna input terminal with a local oscillation signal to convert it to an intermediate frequency signal, and a detection circuit that detects the intermediate frequency signal and outputs an audio frequency signal. In a wireless receiver that outputs a signal from an output terminal through a switch unit of a squelch circuit, a detection circuit that generates a detection output proportional to the reception signal and a transmitter that is a generation source of the reception signal are within its use area. A minimum value storage circuit that stores the minimum value of the detection output in the state of moving, and compares the detection output with the minimum value, and closes the switch unit when the detection output is equal to or more than the minimum value. And a comparison circuit that outputs a control signal.

A receiver of a second invention is the receiver of the first invention, wherein an adder circuit for subtracting a predetermined value from the minimum value is provided, and the comparator circuit outputs the detection output and the output of the adder circuit. And a control signal for closing the switch section is output when the detected output is equal to or higher than the output of the adder circuit.

The receiver of the third invention is the receiver of the first or second invention, wherein an integrating circuit for integrating the detected output with a predetermined time constant is provided, and the minimum value storage circuit is the integrating circuit. The minimum value of the integrated output of is stored.

[0015]

According to the first aspect of the present invention, in this receiver, the detection output output from the detection circuit and the minimum value stored in the minimum value storage circuit are compared by the comparison circuit, and the detection output is the minimum value. It has a squelch circuit that closes the switch section only when the size is above. Therefore, the minimum value is the squelch level of this squelch circuit. The detection output is proportional to the strength of the radio wave received by the antenna (hereinafter referred to as the antenna input). In other words, comparing the detected output with the above-mentioned minimum value means comparing the antenna input with the minimum value of the antenna input (hereinafter referred to as the minimum value of the antenna input) when the transmitter moves within the usage area. It corresponds to that. Therefore, when the antenna input is at a level equal to or higher than the antenna input minimum value, the switch unit is closed, whereby the audio signal is output from the output terminal.

Further, the receiver and the transmitter (hereinafter referred to as the present apparatus) are used in a state where they are in a line of sight or close to each other. Another wireless device (hereinafter referred to as a jamming device) that gives a jamming radio wave to the device is generally used in a remote place outside the usage area of the device.
Therefore, the strength of the jamming radio wave transmitted from the jamming device is considerably weaker than the strength of the sending / receiving radio wave of the device. That is,
The antenna input due to the jamming radio wave is at a level smaller than the above antenna input minimum value. Therefore, when the radio wave is no longer transmitted from the transmitter, the antenna input of the receiver becomes smaller than the minimum antenna input value, which causes the switch part of the squelch circuit to open and enter the muting state, so that the interference radio wave is received. No noise is generated by doing this.

Further, the minimum value as the squelch level is automatically stored by the minimum value storage circuit. Therefore, it is not necessary to manually adjust the squelch level while monitoring the reception state of the receiver.

According to the second invention, the squelch level is the output of the adder circuit, that is, the value obtained by subtracting a predetermined value from the minimum value in the first invention. Therefore, the squelch level is lower than the squelch level in the first aspect by a predetermined value.

According to the third invention, the detection output in the first or second invention is inputted to the minimum value storage circuit after being integrated by the integrating circuit. That is, the minimum value of the integrated output or the value obtained by subtracting a predetermined value from the minimum value of the integrated output by the adder circuit becomes the squelch level of this receiver. Therefore, even if the antenna input fluctuates greatly due to some influence and the detection output fluctuates greatly, if the fluctuation is instantaneous, the fluctuation can be reduced by the integrating circuit.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a receiver according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the receiver of the first embodiment. Referring to FIG. 1, the reception signal input from the antenna input terminal 1 is amplified by the high frequency amplifier 3, and is mixed by the mixer 5 in the local oscillator 7
It is mixed with a signal supplied from and converted into an intermediate frequency signal. The intermediate frequency signal is amplified by the intermediate frequency amplifier 9, and the audio frequency signal is detected by the detection circuit 11. The audio signal is passed through the buffer amplifier 13 and the squelch circuit 37.
It is output from the output terminal 39 via the switch unit 15.

Further, the audio frequency signal output from the detection circuit 11 is supplied to the noise detection circuit 23, and the noise detection output is generated by the noise detection circuit 23, and the noise detection output is output from the voltage comparator 35. It is input to the non-inverting input terminal. The noise detection circuit 23 includes a high-pass filter 17 that passes only a noise component having a frequency exceeding the audible frequency, a noise amplifier 19 that amplifies the noise component, and a noise detection circuit 21 that detects the noise component. The relationship between the noise detection output and the antenna input (reception intensity), as shown in FIG. 2, the noise detection output V ₂₃ is proportional to the antenna input E, i.e. the received signal to a saturation level V _M. Further, when the noise detection output V ₂₃ is in saturation level V _M, the receiver is able to receive the radio waves transmitted by the transmitter at the highest sensitivity.

Further, the noise detection output output from the noise detection circuit 23 is integrated by the integration circuit 25, and A
After being digitized by the / D converter 27, it is input to the minimum value storage circuit 29.

The minimum value storage circuit 29 is composed of, for example, a microcomputer and the like, and a squelch level automatic adjustment switch (not shown) provided in the receiver.
Hereinafter referred to as an automatic adjustment switch. ) Is in the ON state, the minimum value of the digitized noise detection output, that is, the minimum noise value is stored. The digitized noise minimum value continues to be stored in the minimum value storage circuit 29 even after the automatic adjustment switch is turned off. Then, by turning on the automatic adjustment switch again, a new minimum noise value is updated and stored.

The digitized noise minimum value stored in the minimum value storage circuit 29 is input to the addition circuit 31. The adder circuit 31 is composed of, for example, a microcomputer, and subtracts a predetermined value from the input noise minimum value. This predetermined value corresponds to the noise detection output ΔV ₂₃ when the antenna input ΔE in FIG. 2 is ΔE = 3 dB, for example. And this adder circuit 3
The output of 1 is analogized by the D / A converter 33 and input to the inverting input terminal of the voltage comparator 35.

The voltage comparator 35 compares the noise detection output input to the non-inverting input terminal with the output of the analogized adder circuit 31 input to the inverting input terminal. Then, when the noise detection output has a voltage value equal to or higher than the output of the analogized addition circuit 31, a control signal for closing the switch unit 15 is output. When the noise detection output is smaller than the analog output of the adder circuit 31, the switch unit 15 is open. The voltage comparator 35 corresponds to a comparison circuit.

The noise detection circuit 23 and the integration circuit 25 are also provided.
, A / D converter 27, minimum value storage circuit 29, and addition circuit 3
1, D / A converter 33, voltage comparator 35, and switch unit 1
The squelch circuit 37 composed of 5 and 5 is a noise squelch system circuit in which a value obtained by subtracting ΔV ₂₃ from the integrated noise minimum value is used as a squelch level.

Next, the operation of the receiver configured as described above for a wireless microphone device will be described. First, the receiver and the microphone are turned on, and then the automatic adjustment switch is turned on. Then, holding this microphone, it will move throughout the usage area. When this movement is completed, the automatic adjustment switch is turned off. With this, the minimum noise value is stored in the minimum value storage circuit 29, and the automatic adjustment of the squelch level is completed.

FIG. 3 shows the relationship between the noise detection output and the squelch level during the automatic squelch level adjustment. V _{23 in} the figure shows a change state of the noise detection output due to moving the microphone in the use area while transmitting the electric wave of the microphone. The minimum value storage circuit 29 stores the minimum noise value V _L1 when the microphone is moving, that is, when the automatic adjustment switch is in the ON state. This noise minimum value V _L1 is subtracted by ΔV ₂₃ by the adder circuit 31. Therefore, the value V _SQ obtained by subtracting ΔV ₂₃ from V _L1 is the squelch level.

After storing the noise minimum value V _L1 ,
That is, the receiver after turning off the automatic adjustment switch closes the switch unit 15 only when the noise detection output V ₂₃ has a voltage value equal to or higher than the squelch level V _SQ , and outputs the audio frequency signal from the output terminal 39. . Here, unless the sending radio waves microphone from outside the area of use, the noise detection output V ₂₃ does not become a voltage level below the noise minimum V _L1. Therefore, as long as it transmits radio waves of the microphone in the area of use, the noise detection output V ₂₃ becomes greater voltage level than the squelch level V _SQ, thereby, always switch unit 15 is closed. That is, the area where the electric wave transmitted by the microphone cannot be received does not occur in the use area.

Further, as shown in FIG. 3, the noise detection output V _N due to the interfering radio wave from the other wireless device never becomes larger than the noise minimum value V _L1 . Because other wireless devices are usually used in a place farther than the distance between the receiver and the microphone affected by the interference wave, the antenna input of the interference wave is the antenna input of the radio wave transmitted by the microphone. It will be much weaker than Therefore, when the radio wave is no longer transmitted from the microphone, the noise detection output V ₂₃ drops to the noise detection output V _N due to the interfering radio wave, and the squelch level V
_{Since the} voltage level becomes lower than _SQ , the switch unit 15 is opened. As a result, the receiver enters the muting state, and the audio frequency signal is not output, so that it is possible to prevent the noise of the receiver which is unpleasant to the sense of hearing and the noise due to the interfering radio waves. As a result, it is possible to prevent interference with radio waves of other wireless devices.

Particularly, in the case of a wireless microphone device, since the frequency of the radio wave used is protected by law, the jamming radio wave affecting the receiver is transmitted from another microphone used in the vicinity. Most things. Further, the strength of the radio wave of the wireless microphone device is relatively small, and there is not much difference in the strength of the radio wave between the individual devices. Therefore, the effect of reducing the squelch circuit 37 with respect to the above-mentioned jamming radio wave is remarkable.

The noise minimum value V _L1 which is the squelch level of this receiver is automatically stored by the minimum value storage circuit 29 while the automatic adjustment switch is ON,
Then, it is kept stored even after the automatic adjustment switch is turned off. Therefore, it is not necessary to manually adjust the squelch level while monitoring the reception status of the receiver, so even if you need to adjust the squelch level while carrying the transmitter around as described above, you can adjust the squelch level by yourself. can do.

Further, as shown in FIG. 3, the voltage level of the squelch level is V _{SQ obtained} by subtracting ΔV ₂₃ from the noise minimum value V _L1 . Therefore, even if the microphone is carried around, a slight change occurs in the antenna input, and even if the noise detection output V ₂₃ drops to a level lower than the noise minimum value V _L1 due to this change, the magnitude of the drop level is ΔV. _When it is smaller than _23, the switch unit 15 of the squelch circuit 37 is not opened. That is, the squelch level V _SQ has a margin of ΔV _{23 with} respect to the noise minimum value V ₂₃ so that the squelch circuit 37 does not frequently operate due to the fluctuation of the radio wave transmitted by the microphone. As a result, the area where the electric wave transmitted by the microphone cannot be received does not reliably occur in the use area.

Further, the noise detection output is integrated by the integrating circuit 25, digitized by the A / D converter 27, and input to the minimum value storage circuit 29. Therefore, when adjusting the squelch level, the dead point causes the antenna input to momentarily become as small as when there is no signal, and even if the noise detection output also momentarily becomes extremely small, this extremely small It is possible to prevent the noise detection output that has been stored as the minimum value from being stored as it is in the minimum value storage circuit 29. In addition, this integration circuit 2
The time constant of 5 may be set to a value equal to or longer than the time to fall into the dead point.

For example, when the frequency of the received signal received by this receiver is 800 MHz, the time constant of this integrating circuit 25 can be determined by the following procedure. As a general principle, it is known that the dead point can be eliminated by moving the microphone by 1/4 wavelength.
A quarter wavelength at 800 MHz is less than 10 cm. Since the walking speed of a human is usually about 1 m / sec, the time required to travel a distance of 10 cm, that is, the time to fall into a dead point is about 0.1 sec. Therefore, the time constant of the integrating circuit 25 is
It may be set to a value sufficiently larger than 0.1 seconds.

The value ΔV subtracted by the adder circuit 31
₂₃ can be set to any value. Also, this adder circuit 31
Can be removed if no margin is needed for the squelch level. Furthermore, the integrating circuit 25 can be eliminated if it is less susceptible to dead points. The switch unit 15 of the squelch circuit 37 can also be configured by a gate circuit. Also, this first
In the embodiment, the operation and effect of the case where the receiver is for a wireless microphone device have been described. However, the receiver is not limited to the receiver for the wireless microphone device, and an area of a limited size such as an interior The same operation and effect as those of the present embodiment are achieved for all wireless devices used in the device.

FIG. 4 is a block diagram of a receiver of the second embodiment, in which the receiver of the first embodiment is used as a diversity receiver. In this diversity receiver, two receiving parts of the receiver of the first embodiment are combined, and the audio signal of the receiver having a better reception condition of the radio wave transmitted from the transmitter is switched by the switching unit 49. It is what is output. The voltage comparator 41 of the switching unit 49 compares the noise detection outputs of the reception signals input from the antenna input terminals 1 and outputs the audio frequency signal of the receiver with the larger noise detection output, Switch parts 45a, 45b, 47a, 47 in combination with the knot circuit 43
b is opened and closed. In the second embodiment, the operation of the circuits other than the switching unit 49 is the same as that of the first embodiment, and therefore, the same parts are designated by the same reference numerals and the description thereof will be omitted. Therefore, the effects are similar to those of the first embodiment, and thus the description thereof will be omitted.

FIG. 5 is a block diagram of a receiver of the third embodiment. The third embodiment is the same as the receiver of the first embodiment except for the configuration other than the squelch circuit 37a, and the same parts are designated by the same reference numerals and the description thereof will be omitted.

The squelch circuit 37a includes an intermediate frequency amplifier 9
The intermediate frequency signal amplified by is input, and the intermediate frequency signal is rectified by the rectifier circuit 24 and input to the non-inverting input terminal of the voltage comparator 35. The relationship between the rectified output output from the rectifier circuit 24 and the antenna input is the same as in the first embodiment, as shown in the graph of FIG.
₂₄ is proportional to the antenna input E until its voltage level is saturated.

Further, the rectified output output from the rectifying circuit 24 is integrated by the integrating circuit 25. After that, the first
Since it has the same configuration as the squelch circuit 37 of the embodiment, detailed description thereof will be omitted.

The difference between the receiver of the third embodiment and the receiver of the first embodiment is that the receiver of the first embodiment squelches the value obtained by subtracting a predetermined value from the integrated minimum noise value. Noise squelch type squelch circuit 3 for level
7 is provided, the receiver of the third embodiment is
The squelch circuit 37a of the carrier squelch system is provided with a value obtained by subtracting a predetermined value from the minimum value of the integrated rectified output as the squelch level.

However, regarding the operation and effect of the third embodiment, the noise detection output V ₂₃ shown in FIG.
₂₄ , the noise minimum value V _L1 is replaced with the minimum value V _L3 of the rectified output, and the margin value ΔV ₂₃ is replaced with ΔV ₂₄ .
The same operation and effect as those of the first embodiment are achieved.

In the third embodiment, the intermediate frequency signal is rectified by the rectifying circuit 24 and supplied to the integrating circuit 25. However, the output signal of the high frequency amplifier 3 is rectified and the integrating circuit 25 is rectified.
May be supplied to.

[0044]

In the receiver of the first invention, the transmitter of the wireless device is held in advance and the radio wave is still being transmitted, and the receiver is moved throughout the use area, and the detection output (reception) of the detection circuit at this time is received. The minimum value of (proportional to the signal) is stored, and this minimum value is the smallest antenna input minimum value among the antenna inputs of the receiver that receives the radio waves transmitted by the transmitter in the usage area. Correspond. Therefore, after storing this minimum value, the antenna input of the receiver when the transmitter is transmitting radio waves in this usage area becomes at least a level equal to or higher than the antenna input minimum value. As a result, when the transmitter is transmitting radio waves in this usage area, the switch section of the squelch circuit is always closed, and the muting state does not occur. Therefore, this receiver has the effect that it can reliably receive the radio waves transmitted by the transmitter within the usage area. That is, there is an effect that the area where the receiver cannot receive the radio wave transmitted by the transmitter does not occur in the use area.

Further, the antenna input due to the interfering radio waves transmitted from other wireless devices has a level smaller than the above-mentioned minimum antenna input value. Therefore, when radio waves are no longer transmitted from the transmitter, the antenna input of the receiver becomes smaller than the minimum antenna input value, which causes the switch section of the squelch circuit to open and enter the muting state, which is uncomfortable to the listener. No noise from the receiver or noise due to reception of jamming radio waves is generated. As a result, it is possible to reduce interference with radio waves of other wireless devices.

Further, since the minimum value as the squelch level is automatically stored by the minimum value storage circuit,
There is no need to manually adjust the squelch level while monitoring the reception status of the receiver. Therefore, when adjusting the squelch level while carrying the transmitter around, there is no need to bother two people as in the conventional case, and the squelch level can be adjusted by one person.

The receiver of the second invention has an adder circuit for subtracting a predetermined value from the minimum value in the receiver of the first invention, and the output of this adder circuit is set to a squelch level. is there. Therefore, this squelch level is the first
In the invention, the squelch level becomes a level lower by a predetermined value than the minimum value. Therefore, even if the transmitter is carried around, a slight change occurs in the antenna input, and even if the level of the detection output drops to a level lower than the above minimum value due to this change, the magnitude of the drop level is the above predetermined value. When the value is smaller than the value, the switch part of the squelch circuit is not opened. Therefore, it is possible to give the squelch level a margin by the above predetermined value so that the squelch circuit does not frequently operate due to the fluctuation of the radio wave transmitted by the transmitter. As a result, this receiver has the effect of being able to receive the radio waves transmitted by the transmitter within the usage area more reliably than in the first aspect of the invention. That is, in the usage area, the area where the receiver cannot receive the radio wave transmitted by the transmitter is the first area.
The invention has the effect that it does not occur more reliably than the invention described in 1.

Then, in order to obtain the above-mentioned squelch level having a proper margin without causing a region where the radio wave transmitted by the transmitter cannot be received by the receiver, the squelch level is repeated several times as in the conventional case. It is not necessary to perform the adjustment of 1 and there is an effect that it can be automatically set by one adjustment.

The receiver of the third invention has an integrating circuit for integrating the detection output of the first or second invention with a predetermined time constant, and integrates when the transmitter moves in the use area. The minimum value of the integrated output of the circuit is stored in the minimum value storage circuit. Therefore, when adjusting the squelch level, the dead point causes the antenna input to momentarily become as small as when there is no signal, which causes the detection output to also momentarily become extremely small.
It is possible to prevent the extremely small detection output from being stored as it is in the minimum value by the minimum value storage circuit. That is, it is possible to prevent the squelch level from becoming an extremely small value due to the influence of the dead point.

[Brief description of drawings]

FIG. 1 is a block diagram of a receiver according to a first embodiment of the present invention.

FIG. 2 is an input / output characteristic showing the relationship between the antenna input and the noise detection output of the receiver according to the first embodiment of the present invention and the relationship between the antenna input and the rectified output of the receiver according to the third embodiment. It is a graph.

FIG. 3 is a graph showing changes in the noise detection output when adjusting the squelch level of the receiver according to the first embodiment of the present invention, and changes in the rectified output when adjusting the squelch level of the receiver according to the third embodiment. Is.

FIG. 4 is a block diagram of a diversity receiver according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a receiver according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Antenna Input Terminal 5 Mixer 7 Local Oscillator 11 Detection Circuit 15 Switch Section 23 Noise Detection Circuit 25 Integration Circuit 29 Minimum Value Storage Circuit 31 Addition Circuit 35 Voltage Comparator 37 Squelch Circuit 39 Output Terminal

Claims (3)

[Claims] 1. A frequency converter that mixes a received signal input from an antenna input terminal with a local oscillation signal to convert it into an intermediate frequency signal, and a detection circuit that detects the intermediate frequency signal and outputs an audio frequency signal. A wireless receiver that outputs the audio frequency signal from an output terminal via a switch unit of a squelch circuit, a detection circuit that generates a detection output proportional to the reception signal, and a transmitter that is a generation source of the reception signal. And a minimum value storage circuit that stores the minimum value of the detection output in a state where the detection output has moved in the usage area, and compares the detection output with the minimum value, and switches the switch when the detection output is the minimum value or more. A comparison circuit for outputting a control signal for closing the unit,
Wireless receiver comprising. 2. The wireless receiver according to claim 1, further comprising an adder circuit that subtracts a predetermined value from the minimum value, and the comparison circuit compares the detection output with the output of the adder circuit. A wireless receiver which outputs a control signal for closing the switch section when the detection output is equal to or higher than the output of the adding circuit. 3. The wireless receiver according to claim 1, further comprising an integrator circuit that integrates the detected output with a predetermined time constant, and the minimum value storage circuit is the minimum value of the integrated output of the integrator circuit. A wireless receiver, characterized by: