Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1987-03-23
1988-02-02
Ng, Jin F.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455200, 455345, H03J 700, H04B 116
Patent
active
047233192
ABSTRACT:
A signal seeking radio receiver is disclosed in which the AGC voltage applied to the RF amplifier is automatically reduced only when a sweep tune signal is present with a signal generated by the detection of a parameter associated with low ambient light typical of nighttime operating. The night signal may be produced by an ambient light sensor or in response to the activation of a vehicle running light. Thus the stop sensitivity of the tuner in signal seeking mode is reduced at night to prevent stopping on undersirable skywave signals but is normal during daytime operation when the running light is not activated. The sweep tune signal may be the fast/slow AGC control signal or mute signal generated during signal seeking; and its removal when the sweep stops on a station provides normal AGC operation for listening, even at night. The AGC voltage is provided to the control electrode of a variable gain RF amplifier through a first impedance; and a second impedance connects the control electrode to the collector of a transistor having a base controlled by the ambient light signal and an emitter controlled by the sweep tune signal. Thus, when the night signal and sweep tune signal are simultaneously present, the transistor conducts to reduce the applied AGC voltage by the proportion of the first to the second impedance. Otherwise, full AGC voltage is applied to the control electrode of the RF amplifier.
REFERENCES:
patent: 2731556 (1956-01-01), Wiley
patent: 2843734 (1958-07-01), Lerch, Jr. et al.
patent: 2958771 (1960-11-01), Mural et al.
patent: 4262363 (1981-04-01), Wiechmann et al.
patent: 4580285 (1986-04-01), Richards, Jr.
1978 Electronically Tuned Receiver, Delco Electronics Service Manual, pp. 12-1 thru 12-10.
General Motors Corporation
Ng Jin F.
Sigler Robert M.
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