Telecommunications – Receiver or analog modulated signal frequency converter – Squelch
Patent
1982-12-27
1983-11-08
Ng, Jin F.
Telecommunications
Receiver or analog modulated signal frequency converter
Squelch
455225, 455303, 381 57, H04B 110
Patent
active
044146892
ABSTRACT:
A squelch circuit for a radio receiver provides for applying the audio signal that has been detected and demodulated to both a low pass channel and high pass channel. The low pass channel passes the audio signal to a low frequency bandpass filter where only the lower frequencies of the demodulated signal are passed. The filtered signal is then average by an averaging detector where the average of the energy contained within the signal is obtained and monitored by a syllabic detector, which upon the occurrence of certain pre-established varying energy levels will indicate the presence of speech in the demodulated signal. The high pass channel includes a high frequency bandpass filter for passing signals with a frequency that is greater than the frequencies of those signals passed by the low frequency bandpass filter, a peak detector for detecting the concentration of signal energy and a level comparator for comparing the output of the averaging detector with the peak detector and to provide a positive indication when the average level is greater than the peak level. The output from the high pass channel and the low pass channel are ANDed together to provide a signal that will operate an audio gate for passing the demodulated signal on to the output means, when the output from the high pass channel, and the output from the low pass channel are ANDed together and provide a positive indication.
REFERENCES:
patent: 3102236 (1963-08-01), Eichenberger et al.
patent: 3350650 (1967-10-01), Kemper
patent: 4187396 (1980-02-01), Luhony
Greenberg Howard R.
Hamann H. Fredrick
Ng Jin F.
Robinson Richard K.
Rockwell International Corporation
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