Method and apparatus for receiving a compressed composite signal

Details Method and apparatus for receiving a compressed composite signal Method and apparatus for receiving a compressed composite signal

1985-12-11

1988-01-05

Ng, Jin F.

Telecommunications

Receiver or analog modulated signal frequency converter

Local control of receiver operation

455 35, 455203, 455260, 455265, 455266, H04B 116

Patent

active

047181168

ABSTRACT:
A compressed single side band communication system and method in which the audio signal is compressed prior to pre-emphasis and thereafter summed with a pilot tone for further compression prior to transmission. Initially, only the pilot tone is transmitted at full rated power to aid in acquisition of the signal by the receiver. Thereafter, the transmitter ALC is disabled and the pilot tone is attenuated. The receiver adjusts the frequency characteristics of the pilot tone filter and phase lock loop filter in the detector as a function of lock-on. The delay after loss of lock-on in reverting to wide band pilot tone and wideband loop filters is varied as a function of signal strength. The pilot tone may be frequency modulated for tone coded squelch, with the modulating source being located in the return end of the phase lock loop filter. A unique filter is provided to insure acquisition of the pilot tone. Automatic gain control of the audio signal is responsive to the tone signal without affecting the composite audio and tone signal. The audio signal and piot tone may be weighted and summed to maintain a constant amplitude signal to the squelch detector to reduce undersired operation in the presence of audio peaks.

REFERENCES:
patent: 3909735 (1975-09-01), Anderson et al.
patent: 4360929 (1982-11-01), Isobe
patent: 4403348 (1983-09-01), Leland et al.

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