UHF electronic tuner
First Claim
1. A UHF varactor tuner comprising:
- preselector means for passing a select radio frequency signal, said preselector means including a housing containing resonant cavities, a plurality of transmission lines and a plurality of varactor diodes for providing variable half-wave tuning of said transmission lines, said transmission lines being contained in respective resonant cavities of said housing and being aperture intercoupled by aperture means in the walls of said resonant cavities;
oscillator means for generating an oscillator signal;
mixer means coupled to heterodyne said oscillator signal with said select radio frequency to result in an intermediate frequency signal; and
said preselector means further including frequency dependent circuit means coupled between said tuned transmission lines and operative primarily at one end of the UHF band of frequencies to augment said aperture intercoupling and thereby provide said preselector means with a substantially uniform bandwidth over the entire UHF band.
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Accused Products
Abstract
A high input selectivity UHF varactor tuner for a television receiver in which unamplified radio frequency signals are inductively coupled to a double tuned half-wave preselector comprising two aperture coupled half-wave tuned lines in separate resonant cavities. The double tuned preselector includes varactor diodes on one end of each tuned line and fixed capacitors on the other end of each line. To compensate for decreasing Q of the varactor diodes with decreasing frequency and thereby maintain a uniform bandwidth for the tuner over the entire UHF spectrum, inductive coupling is provided between the tuned lines at the fixed capacitor ends which, during low frequency operation of the tuner, augments aperture coupling between the lines.
72 Citations
12 Claims
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1. A UHF varactor tuner comprising:
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preselector means for passing a select radio frequency signal, said preselector means including a housing containing resonant cavities, a plurality of transmission lines and a plurality of varactor diodes for providing variable half-wave tuning of said transmission lines, said transmission lines being contained in respective resonant cavities of said housing and being aperture intercoupled by aperture means in the walls of said resonant cavities; oscillator means for generating an oscillator signal; mixer means coupled to heterodyne said oscillator signal with said select radio frequency to result in an intermediate frequency signal; and said preselector means further including frequency dependent circuit means coupled between said tuned transmission lines and operative primarily at one end of the UHF band of frequencies to augment said aperture intercoupling and thereby provide said preselector means with a substantially uniform bandwidth over the entire UHF band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A constant bandwidth UHF tuner comprising:
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first and second resonant cavities, two transmission lines, two capacitors, and two varactor diodes, said transmission lines being housed respectively in said first and second resonant cavities in half-wave tuning configurations with one of said capacitors connected between a first end of each line and each respective cavity and with one of said varactor diodes connected between a second end of each line and each respective cavity; variable voltage means for biasing said varactor diodes to tune said lines to a select radio frequency signal; radio frequency coupling means for introducing an unamplified ratio frequency signal to said first cavity; aperture coupling means between said first and second cavities; oscillator means for generating an oscillator signal; mixer means coupled to heterodyne said oscillator signal with said select radio frequency signal as passed by said resonant cavities to result in an intermediate frequency signal; and frequency dependent coupling means inductively linking together said first end of said transmission line in said first cavity and said first end of said transmission line in said second cavity during operation of said tuner at the lower portions of the UHF frequency spectrum to provide said tuner with a substantially uniform bandwidth over the entire UHF frequency spectrum. - View Dependent Claims (10, 11, 12)
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Specification