Television – Receiver circuitry – Tuning
Patent
1991-12-30
1995-05-30
Groody, James J.
Television
Receiver circuitry
Tuning
348733, 4551651, 4551831, 455209, H04N 550
Patent
active
054206464
ABSTRACT:
A double conversion type television tuning system for a digital television signal includes a synthesizer for developing a tuning voltage for the upconverter. The synthesizer provides bandswitching for dividing the tuning range into four portions and includes a separate local oscillator for each portion. Each local oscillator is enabled by a transistor that is switched by a bandswitch voltage. The output of each oscillator is applied through respective bandswitched buffer amplifiers to an arrangement of three 3 dB hybrid couplers to convey the appropriate local oscillator signal to the upconverter mixer. The system minimizes phase noise and jitter which is essential when operating with digital signals.
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patent: 2460900 (1949-02-01), Newbold
patent: 3909751 (1975-09-01), Tang et al.
patent: 4402089 (1983-05-01), Knight et al.
patent: 4551856 (1985-11-01), Victor et al.
patent: 4811362 (1989-03-01), Yester, Jr. et al.
patent: 4922548 (1990-05-01), Cowley
patent: 4947456 (1990-08-01), Atkinson et al.
patent: 4996597 (1991-02-01), Duffield
patent: 5148452 (1992-09-01), Kennedy et al.
Burgess Glenton B.
Groody James J.
Zenith Electronics Corp.
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