JPS6246348Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a squelch circuit in an SSB receiver.

Conventionally, as shown in FIG. 1, in an SSB receiver consisting of a bandpass filter 1, an amplifier 2, an SSB signal demodulator 3, a low frequency amplifier 4, and a speaker 5 connected to an IF stage, the squelch circuit includes a rectifier circuit 6, Consists of a DC amplifier 7, a switching circuit 8, etc.
The SSB signal that has been amplified by the bandpass filter 1 and amplifier 2 after passing through a receiving circuit such as IF is rectified by the rectifier circuit 6, and then amplified by the DC amplifier 7 to generate a DC signal that changes depending on the magnitude of the signal from the amplifier 2. A voltage is obtained, and the switching circuit 8 is controlled by this DC voltage to perform a squelch operation.

However, since the squelch circuit with this configuration detects the amplitude component of the SSB wave, it has the disadvantage that the squelch operation becomes unstable when the SSB wave is around the same level as the noise. .

In addition, in conventional circuits, SSB at a minute level
Detecting waves not only requires a linear amplifier circuit with a large gain, but even if this is used, it is difficult to operate stably, so the squelch sensitivity is limited to -6 dBμ at most. .

In addition, it is necessary to adjust the squelch threshold level each time the noise level fluctuates, and there are various drawbacks, such as malfunctions caused by external noise such as ignition pulses. The object of this invention is to provide a squelch circuit for an SSB receiver that can eliminate the drawbacks of the conventional circuit described above and can operate stably even if the SSB wave is at the same level as the noise.

An embodiment of the present invention will be described below based on FIG. 2.

In the figure, 9 is an amplitude limiter connected to the amplifier 2, 10 is a frequency discriminator, 11 is a high-pass filter, and 12 is a noise amplifier, and the same components as in FIG. 1 are given the same symbols. It has been done.

Next, an example of the operation of this circuit will be described. First, the SSB signal that has passed through the bandpass filter 1 and the amplifier 2 is limited to a constant amplitude by the amplitude limiter 9, and is input to the frequency discriminator 10. Such a frequency discriminator 10 is originally used for demodulating FM waves, but in the present invention, it is used as a signal and noise separation circuit. When an SSB wave is input to this, noise components other than the signal are suppressed.
The main component is the fluctuation of the voice formant (like the tremor of the voice) in the SSB signal, but since the fluctuation component of the voice formant fluctuates relatively slowly, most of its output is in the low frequency range. Becomes an ingredient. On the other hand, if only noise is simply input to the frequency discriminator 10, the fluctuations occur irregularly, so that all band components including high frequencies are obtained as a large output.

Therefore, by using the difference in the distribution of the output frequency of the frequency discriminator 10 when the SSB signal is input and when only noise is input as described above, it is possible to calculate the output frequency of the frequency discriminator 10 when only noise is input. The detected noise detected component (high frequency component) is taken out by the high-pass filter 11, amplified by the noise amplifier 12, rectified by the rectifier circuit 6, and then amplified by the DC amplifier 7. This controls so that the audio signal is blocked. In addition, when an SSB signal is input, the output signal of the frequency discriminator 10 mainly contains low frequency components and contains almost no high frequency components, so there is no component that passes through the high pass filter 11 and the DC amplifier The input to 7 is gone and the squelch is now open. When configured as described above, extremely high squelch sensitivity of -16 dBμ or less can be obtained.

According to the squelch circuit of the SSB receiver according to the present invention, by passing the SSB signal waveformed by the bandpass filter and amplified through the amplitude limiter and the frequency discriminator, it is possible to determine whether the SSB signal is being received or when there is no signal. Since it is configured to obtain a signal with a different frequency distribution and perform a squelch operation, it is possible to reduce malfunctions due to noise, and it does not depend on the size of the SSB input signal, that is, the SSB input signal is the same as the noise. Stable squelch operation can be obtained even at low levels. Furthermore, the squelch sensitivity is extremely high, and the squelch can be opened even with a weak signal, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a squelch circuit of a conventional SSB receiver, and FIG. 2 is a block diagram showing an embodiment of the squelch circuit of an SSB receiver according to the present invention. 1: Band filter, 9: Amplitude limiter, 10: Frequency discriminator, 11: High pass filter, 12: Noise amplifier, 6: Rectifier, 7: DC amplifier, 3:
SSB demodulator.

Claims (1)

[Claims for Utility Model Registration] A band filter connected to the IF stage, an amplifier connected to the band filter, an SSB demodulation circuit connected to the amplifier, and a low frequency amplifier connected to the SSB demodulation circuit. An SSB receiver comprising: an amplitude limiter connected to the amplifier; a frequency discriminator connected to the amplitude limiter; a high-pass filter connected to the frequency discriminator; a connected noise amplifier, a noise detector connected to the noise amplifier, a DC amplifier connected to the noise detector, and the SSB demodulation circuit and the low frequency amplifier connected to the DC amplifier. and a switching circuit provided between the
Ssb receiver squelch circuit.