Telecommunications – Receiver or analog modulated signal frequency converter – Squelch
Patent
1986-09-30
1988-03-15
Masinick, Michael A.
Telecommunications
Receiver or analog modulated signal frequency converter
Squelch
455218, 455222, H04B 110
Patent
active
047318732
ABSTRACT:
A squelch trigger circuit for use in an RF receiver for receiving a modulated carrier signal having a predetermined information band, and producing a squelch trigger signal. The squelch trigger circuit includes a bandpass filter connected to receive the modulated carrier signal and having a passband that includes the information band. The output of the bandpass filter is connected to an AGC circuit that includes a detector for producing a detection signal indicative of the level of the AGC output signal. The detection signal is input to a high pass filter having a corner frequency selected such that the noise signal includes only frequency components higher than one-half of the passband of the bandpass filter, such that the noise signal produced by the high pass filter corresponds to the out of band noise components of the AGC output signal. The noise signal is input to a noise detector for producing a noise level signal, and the noise level signal is compared to a threshold to produce the squelch trigger signal. The threshold may be temperature compensated to model thermal noise in the AGC circuit.
REFERENCES:
patent: 3188571 (1965-06-01), Michael
patent: 3323066 (1967-05-01), Kurtz
patent: 3325738 (1967-06-01), Busby
patent: 3337808 (1967-08-01), Kalin
patent: 3569840 (1971-03-01), Tanaka et al.
patent: 4041390 (1977-08-01), Schroeder
patent: 4143331 (1979-03-01), Page
patent: 4388731 (1983-06-01), King
patent: 4411021 (1983-10-01), Yoakum
patent: 4480335 (1984-10-01), Kishi
Masinick Michael A.
The Boeing Company
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