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US 4,361,909 AGranted
Pre-tuner tracking traps responsive to a tuning voltage
AssigneeRCA Corporation
InventorGerald E. Theriault
Life of this patent
Estimating the term…
Abstract
In a television receiver, two tunable traps are incorporated between the RF input and the tuner to attenuate undesired signals symmetrically located in frequency below and above respective desired RF carriers. In one embodiment, the tunable traps are responsive to a tuning voltage for controlling the tuned circuits of the tuner so that the attenuation frequencies of the traps track the frequencies of the RF carriers associated with selected channels. In another embodiment the attenuation frequencies of the traps are moved with respect to the respective frequencies of desired RF carriers to optimize interference reduction.
Claims10
In a receiver, apparatus comprising:
- RF input means for supplying RF carriers;
- tuning control means for generating a tuning voltage having magnitudes corresponding to respective selected channels;
- local oscillator means for generating a local oscillator signal having frequencies determined by respective magnitudes of said tuning voltage;
- mixer means for combining a selected one of said RF carriers and said local oscillator signal to produce an IF signal;
- RF tuner means for selectively applying ones of said RF carriers having frequencies determined by respective magnitudes of said tuning voltage to said mixer means;
- connection means for coupling said RF input means to said RF tuner means;
- and
- first signal rejection means coupled to said connection means for attenuating undesired signals at a predetermined negative frequency offset from respective desired RF carriers in response to respective magnitudes of said tuning voltage;
- and
- second signal rejection means connected to said connection means for attenuating undesired signals at a predetermined positive frequency offset from respective desired RF carriers in response to respective magnitudes of said tuning voltage.
7 more elements
In a receiver, apparatus comprising:
- RF input means for supplying RF carriers;
- tuning control means for generating a tuning voltage having magnitudes corresponding to respective selected channels;
- local oscillator means for generating a local oscillator signal having frequencies determined by respective magnitudes of said tuning voltage;
- mixer means for combining a selected one of said RF carriers and said local oscillator signal to produce an IF signal;
- RF tuner means for selectively applying ones of said RF carriers having frequencies determined by respective magnitudes of said tuning voltage to said mixer means;
- connection means for coupling said RF input means to said RF tuner means;
- first signal rejection means coupled to said connection means for attenuating undesired signals at negative frequency offsets from respective desired RF carriers in response to respective magnitudes of a first control voltage;
- second signal rejection means coupled to said connection means for attenuating undesired signals at positive frequency offsets from respective desired RF carriers in response to respective magnitudes of a second control voltage;
- and
- signal rejection control means for generating said first and second control voltages and for controlling their magnitudes to control said negative and positive frequency offsets, respectively.
7 more elements
In a receiver, apparatus comprising:
- RF input means for supplying RF carriers;
- tuning control means for generating a tuning voltage having magnitudes corresponding to respective selected channels;
- local oscillator means for generating a local oscillator signal having frequencies determined by respective magnitudes of said tuning voltage;
- mixer means for combining a selected one of said RF carriers and said local oscillator signal to produce an IF signal;
- RF tuner means for selectively applying ones of said RF carriers in a predetermined frequency range having frequencies determined by respective magnitudes of said tuning voltage to said mixer means;
- a conductor coupled between said RF input means to said RF tuner means;
- first and second signal rejection means connected to said connection means between said RF input means and said RF tuner means for attenuating undesired signals having frequencies at predetermined negative and positive frequency offsets from respective desired RF carriers in response to respective magnitudes of said tuning voltage;
- said signal rejection means including a capacitor, a varactor diode and a first inductor connected in the order named in series combination between a point along said conductor and a point of reference potential, said tuning voltage being applied to one of the cathode and anode electrodes of said varactor diode;
- and
- a second inductor connected in parallel combination to said series combination of each of said signal rejection between said point along said conductor and said point of reference potential, said inductor presenting a negligible large impedance between said point along said conductor and said point of reference potential in said predetermined range and at frequencies at which said signal rejection means attenuate said undesired signals.
7 more elements
Dependencies are inferred from the claim text.