Phase lock loop electronic tuning system

Claim 2

A tuning system for a superheterodyne receiver having a mixer stage, said tuning system including in combination: a voltage controlled oscillator for supplying tuning signals of varying frequency to the mixer stage in response to a tuning voltage applied thereto; a phase-lock loop system for supplying a tuning voltage to said voltage controlled oscillator, said loop system including reference oscillator means, and a phase detector stage coupled with the outputs of said reference oscillator means and the mixer stage for producing said tuning voltage; and first and second overriding means coupled with said voltage controlled oscillator for selectively overriding the output of said phase detector stage, each of said first and second overriding means having set and reset stages of operation, said first overriding means in said set state of operation causing the frequency of said voltage controlled oscillator to increase in a predetermined manner and said second overriding means in said set state of operation causing the frequency of said voltage controlled oscillator to decrease in a predetermined manner; and means for independently, selectively changing the states of said first and second overriding means from the reset state of operation to the set state of operation.

Claim 3

The combination according to claim 1 wherein said first and second overriding means comprise first and second bistable flip-flop means, respectively, each having a reset and a set state of operation and further including means coupled with the output of the mixer stage for resetting said first ans second flip-flop means to their reset state of operation in response to a predetermined signal level at the output of the mixer stage.

Claim 4

The combination according to claim 2 wherein said resettIng means comprises automatic gain control circuit means for producing a reset pulse applied to said flip-flop means.

Claim 5

A signal seeking tuning system for a superheterodyne television receiver having a mixer with at least two inputs and an output, with received signals applied to one of the inputs thereof and producing a video IF carrier frequency on the output thereof when said receiver is tuned to a transmitted channel, said tuning system including in combination: voltage controlled oscillator means, with an output coupled to the other input of the mixer and having a control input for receiving a control voltage to vary the frequency of the output signal thereof in response to said control voltage; reference oscillator means producing an output signal at the desired video IF carrier frequency of the receiver; phase detector circuit means with a first input coupled with the mixer output and the second input coupled with the output of said reference oscillator means, said phase detector circuit means having at least one output and producing an output signal thereon indicative of the frequency and phase relationship of signals applied to the first and second inputs thereof; charge storage means; gating circuit means having first and second outputs coupled with said charge storage means, and coupled to respond to the output of said phase detector circuit means and having at least two additional inputs; coupling means coupling said charge storage means with said control input of said voltage control oscillator; first and second normally reset tuning control means having first and second outputs coupled respectively to said two additional inputs of said gating circuit means, each of said tuning control means being selectively settable from a reset state to a set state of operation for producing signals on the outputs of said gating circuit means to increase the charge on said charge storage means when said first tuning control means is changed to its set state of operation and for decreasing the charge on said charge storage means when said second tuning control means is in its set state of operation, thereby overriding the output signal of said phase detector circuit means.

Claim 6

A signal seeking tuning system for a superheterodyne television receiver having a mixer with at least two inputs and an output, with received signals applied to one of the inputs thereof and producing a video IF carrier frequency on the output thereof when said receiver is tuned to a transmitted channel, said tuning system including in combination: voltage controlled oscillator means, with an output coupled to the other input of the mixer and having a control input for receiving a control voltage to vary the frequency of the output signal thereof in response to said control voltage; reference oscillator means producing an output signal at the desired video IF carrier frequency of the receiver; phase detector circuit means with a first input coupled with the mixer output and the second input coupled with the output of said reference oscillator means, said phase detector circuit means having at least one output and producing an output signal thereon indicative of the frequency and phase relationship of signals applied to the first and second inputs thereof; charge storage means; gating circuit means having first and second outputs coupled with said charge storage means, and coupled to respond to the output of said phase detector circuit means and having at least two additional inputs; coupling means coupling said charge storage means with said control input of said voltage control oscillator; first and second normally reset tuning control means having first and second outputs coupled respectively to said two additional inputs of said gating circuit means, each of said tuning control means being selectively settable from a reset state to a set state of operation for producing signals on the outputs of said gating circuit means to increase the charge on said charge storage means when said first tuning control means is changed to its set state of operation and for decreasing the charge on said charge storage means when said second tuning control means is in its set state of operation, thereby overriding the output signal of said phase detector circuit means.

Claim 7

The combination according to claim 4 further including means coupled with the output of the mixer and responsive to a predetermined output signal thereof for resetting said tuning control means.

Claim 8

The combination according to claim 5 wherein said phase detector circuit means is a digital phase detector with first and second outputs; said gating circuit means comprises first and second gate means each having at least first and second inputs; with the first input of said first and second gate means being coupled respectively with the first and second outputs of said phase detector circuit means; said first and second tuning control means comprise first and second flip-flop means respectively, with the output of said first flip-flop means being connected respectively with the second input of said first gate means and the output of said second flip-flop means being connected with the second input of said second gate means, and further comprise means for selectively changing the state of each of said first and second flip-flop means from a reset condition to a set condition to change the state of the output thereof accordingly; and the outputs of said first and second gate means are coupled with said charge storage means to control the charge stored thereon.

Claim 9

The combination according to claim 6 wherein said resetting means resets said first and second flip-flop means from a set state to a reset state.

Claim 10

The combination according to claim 7 wherein said receiver includes an IF amplifier connected to the output of the mixer and said resetting means comprises means coupled with the output of the IF amplifier and responsive to the magnitude of signal appearing on such output for resetting said first and second flip-flop means in response to a signal iN excess of a predetermined magnitude.