JP3249586B2 - Squelch circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a squelch circuit,
In particular, the present invention relates to a squelch circuit having a squelch tail notification function.

[0002]

2. Description of the Related Art When the level of a noise component of a demodulated output does not exceed a threshold, a gate is opened and the demodulated output is output to a speaker. When the level of a noise component of the demodulated output exceeds a threshold, the gate is closed and noise is reduced. It is a squelch circuit that does not leave the speaker.

FIG. 4 is a block diagram of a conventional squelch circuit. As shown in FIG. 4, a noise component is extracted from a subsequent stage of the detection circuit 12 by a noise filter 21 and integrated by an integration circuit 23. When the level is smaller than a predetermined threshold, the squelch gate 20 is opened and squelch-opened when there is a received signal. .

[0004] In such a configuration, when the received signal suddenly hears the noise of "zar", it can be determined that the squelch tail.

[0005]

In recent years, the use of transceivers for data transmission has begun to spread widely, and for the purpose of responding to this demand, a higher speed is required for the squelch operation.

[0006] As a result, the squelch tail does not generate the above-mentioned sound of "za" but only a shorter sound of "pull", which makes the squelch tail difficult to understand.

The present invention has been proposed in view of the above-described conventional circumstances, and has as its object to provide a squelch circuit in which a squelch tail can be easily determined.

[0008]

The present invention employs the following means to achieve the above object. That is, in a squelch circuit that opens and closes a squelch gate depending on whether or not the demodulated output includes noise, as shown in FIG.
When the analog signal Sc obtained by integrating the noise signal Sb has reached a predetermined threshold, the squelch gate is closed.
A waveform shaping circuit 24 which outputs a square wave, the notification in the operating state
The notification sound output circuit 32 that outputs sound and the rise of the square wave
Of operating the notification sound output circuit 32 for a predetermined time from
And a logic circuit 31 .

Further, in order to implement the present invention digitally, the present invention is configured as follows. That is, in the squelch circuit, as shown in FIG. 3, a sampling circuit 25 that samples a noise signal Sb obtained by filtering a demodulated signal and detects the number of times the noise signal appears within a predetermined time , Notification sound to output notification sound
The output circuit 32 and the circuit obtained from the sampling circuit 25
The sampling circuit 25 compares the numerical value with a predetermined number of times.
When the value of the number of times obtained from the
While controlling to close the kerch gate 20,
The number of times obtained from the sampling circuit 25 is a predetermined set number of times.
The notification sound output circuit 32 is turned on for a predetermined time after
And an operation circuit 26 that operates .

[0010]

When the analog signal obtained by integrating the noise signal reaches a predetermined threshold, a square wave is formed by the waveform shaping circuit. In response to the square wave Sd, the logic circuit 31 activates a predetermined time notification sound output circuit 32 to emit a beep sound. As a result, even in the case of high-speed squelch, the reception end can be confirmed aurally.

When the received signal is lost, the level of the noise signal increases. This noise signal has a wide frequency band, and the number of times the sampling circuit 25 samples a signal of a predetermined level or higher at a frequency higher than that of the audio signal within a predetermined time within the predetermined time becomes extremely larger than when a received signal is input. Therefore, the arithmetic circuit 26 having the comparing function as described above compares the count value obtained from the sampling circuit 25 with a predetermined set value, and when the count value obtained from the sampling circuit 25 by this comparison is larger. , A beep sound for notifying that the reception signal has disappeared and ending the call is output from the notification sound output circuit 32.

[0012]

FIG. 1 is a block diagram of an embodiment in which the present invention is applied to an analog system, and FIG. 2 is a waveform diagram of each part of FIG.

As in the prior art, the output of the intermediate frequency amplifier 11 is detected by the detection circuit 12 to extract a low frequency signal.
The low-frequency signal is supplied to the speaker 1 via the de-emphasis circuit 13, the squelch gate 20, and the power amplifier 14.
5 is input.

The output of the detection circuit 12 (FIG. 2A) is branched to a noise filter 21, where a noise component (FIG. 2B) is extracted by a noise filter 22.
Is input to The noise signal amplified by the noise amplifier 22 is integrated by the integration circuit 23 at the next stage as shown in FIG. 2C, and the value of the analog signal Sc output from the integration circuit 23 becomes equal to or larger than a predetermined threshold value. 2D, the waveform shaping circuit 24 outputs a square wave Sd as shown in FIG.
The squelch gate 20 is closed by the square wave Sd.

As described above, the square wave Sd for driving the squelch gate is also input to the logic circuit 31.
Start In the logic circuit 31, a time for operating the next-stage notification sound output circuit 32 is set, whereby the notification sound output circuit 32 operates at the same time as the squelch gate 20 is closed, and as shown in FIG. As shown, a beep sound is obtained, and the end of reception can be determined.

FIG. 3 is a block diagram of an embodiment in which the present invention is applied to a digital system. The output from the detection circuit 12 is input to a sampling circuit 25, where the state in which the noise component has exceeded a predetermined level value is sampled, and the number of times n sampled within a predetermined time is sent to the next-stage arithmetic circuit 26. Is output.

The arithmetic circuit 26 compares the count value n obtained from the sampling circuit 25 as described above with a predetermined count value N set in advance, and calculates the count value n.
Outputs a gate control signal for turning off the squelch gate 20 when the number exceeds the predetermined number of times N. At the same time, the control signal for operating the next-stage notification sound output circuit 32 is turned on at a predetermined time. As a result, the squelch gate 20 is turned off and the notification sound output circuit 3
2 generates a beep sound for a predetermined time to notify the operator of the end of the call.

[0018]

As described above, according to the present invention, the squelch gate closes when there is no reception input, and a beep sound is generated from the notification sound output circuit, so that it is easy to determine the end of reception. .

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment in which the present invention is applied to an analog system.

FIG. 2 is a waveform diagram of each part of FIG.

FIG. 3 is a block diagram of an embodiment in which the present invention is applied to a digital system.

FIG. 4 is a block diagram of a conventional squelch circuit.

[Explanation of symbols]

 Reference Signs List 20 squelch gate 24 waveform shaping circuit 25 sampling circuit 26 arithmetic circuit 31 logic circuit 32 notification sound output circuit Sb noise signal Sc analog signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-168428 (JP, A) JP-A-58-54142 (JP, U) JP-A-63-16181 (JP, Y2) (58) Field (Int.Cl. ⁷ , DB name) H04B 1/10

Claims (2)

(57) [Claims] 1. A squelch circuit for opening and closing a squelch gate depending on whether or not a demodulated output contains noise, wherein the squelch gate is closed when an analog signal obtained by integrating a noise signal reaches a predetermined threshold . square
Waveform shaping circuit that outputs waves and annunciation sounds when activated
From the rising edge of the square wave
A squelch circuit including a logic circuit that activates the notification sound output circuit for a predetermined time . 2. A squelch circuit for opening and closing the squelch gate depending on whether the noisy the demodulation output, and a sampling circuit for detecting the number of times that the noise signal appears within a predetermined time by sampling the demodulated signal, operation
A notification sound output circuit for outputting a notification sound in a state;
Compare the number of times obtained from the ring circuit with the specified number of times
And the number of times obtained from the sampling circuit is
Close the squelch gate when the set number of times is exceeded
Control from the sampling circuit.
From the time when the number of times
A squelch circuit comprising an arithmetic circuit that activates the notification sound output circuit during the period of time .