Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1980-06-30
1983-01-11
Chin, Tommy P.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455187, H04B 116, H03J 524
Patent
active
043685412
ABSTRACT:
A multiplexing arrangement enables a plurality of control voltages for controlling respective ones of a plurality of varactor controlled tunable filters, employed, e.g., prior to the tuner of a television receiver to reject undesired signals, to be generated by a single digital to analog (D/A) converter. A controller, which may, e.g., comprise a microcomputer, sequentially applies digital control words to the D/A converter and substantially synchronously causes the resultant control voltages generated by the D/A converter to be applied, through respective switches to the tunable filters. The control voltages are applied to capacitors connected to d.c. control lines for the tunable filters. The high impedance of the varactor diodes included in the filters enables the capacitors to store respective control voltages for relatively long intervals before the control voltages need to be refreshed. This enables a large number of tunable filters to be controlled by a single D/A converter.
REFERENCES:
patent: 3550010 (1970-12-01), Byers
patent: 3652960 (1972-03-01), Sakamoto
patent: 3696302 (1972-10-01), Gossard
patent: 3778736 (1973-12-01), Sakamoto
patent: 3852670 (1974-12-01), Ma
patent: 3924191 (1975-12-01), Collins
patent: 4011515 (1977-03-01), Hanson
patent: 4123717 (1978-10-01), Yiu
patent: 4153887 (1979-05-01), Poppa
patent: 4209751 (1980-06-01), Sakamoto
Digital Logic Handbook, C-105, published in 1967 by Digital Equipment Corp., p. 284.
"A Systems Approach to Low-Cost Electronic Tuning Address" by B. Howell, J. Reid, F. Zlotnick, IEEE Transactions on Consumer Electronics, vol. CE-24, No. 3, Aug. 1978, pp. 408-418.
Chin Tommy P.
Emanuel P. M.
Rasmussen P. J.
Whitacre E. M.
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