Signal processing system for television receiver having acoustic surface wave devices for improved tuning and video demodulation

Claim 2

In a television reader, a system comprising: tuner means for selecting a desired RF video channel and for converting a selected RF video carrier to a carrier at a predetermined IF video carrier frequency; an IF stage coupled to said tuner means including an acoustic surface wave IF bandpass filter for shaping the frequency response characteristic of the IF stage; video demodulating means for demodulating said IF video carrier to produce a video signal; and control means, including means establishing a reference frequency, being responsive to an IF signal from said IF stage for causing said system to automatically seek a frequency alignment between said IF video carrier frequency and said reference frequency, said system being characterized by having a frequency sensitive acoustic surface wave device in at least one of said demodulating means and said control means, said acoustic surface wave IF bandpass filter and said surface wave devices having similar thermal response characteristics and similar ambient thermal exposure so as to cause temperature tracking of the frequency characteristics of said IF stage and of said device.

Claim 3

The system defined by claim 1 Which includes in said tuner means a voltage-controlled local oscillator, and wherein said control means includes an AFC loop which includes said tuner means and which has an acoustic surface wave discriminator constituting said surface wave device having a center frequency constituting said reference frequency, said discriminator generating a control signal for adjusting the tuning of said voltage-controlled local oscillator to effect said frequency alignment.

Claim 4

The system defined by claim 1 wherein said video demodulating means comprise a synchronous detector, and wherein said system includes reference oscillator means for establishing a reference demodulation frequency for said synchronous detector, said reference oscillator means including a frequency selective surface wave device constituting said surface wave device for establishing the frequency of oscillation of said oscillator.

Claim 5

The system defined by claim 3 which includes in said tuner means a voltage-controlled local oscillator, and wherein said control means includes an AFC loop which includes said tuner means and which has an acoustic surface wave discriminator constituting said surface wave device having a center frequency establishing said reference frequency, said discriminator generating a control signal for adjusting the tuning of said voltage-controlled local oscillator to effect said frequency alignment.

Claim 6

In a television receiver, a system comprising: tuner means for selecting a desired RF video channel and for converting a selected RF video carrier to a video carrier at a predetermined IF video carrier frequency, said tuner means including a voltage-controlled local oscillator; an IF stage coupled to said tuner means including an acoustic surface wave IF bandpass filter for shaping the frequency response characteristic of the IF stage, said acoustic surface wave If bandpass filter having a first thermal response characteristic; video demodulating means for demodulating an IF signal from said IF stage to produce a video signal; and control means responsive to an IF signal from said IF stage and comprising an AFC loop including said tuner means, said control means including an acoustic surface wave discriminator having a center frequency, said discriminator generating a control signal for adjusting the tuning of said voltage-controlled local oscillator to cause said system to automatically seek a frequency alignment between said IF video carrier frequency and said center frequency, said acoustic surface wave discriminator having a second thermal response characteristic, the thermal response characteristics of said bandpass filter and said discriminator being similar; and means exposing said bandpass filter and said discriminator to similar ambient temperatures to cause temperature tracking of the frequency characteristics of said IF stage and of said AFC loop.

Claim 7

In a television receiver, a system comprising: tuner means for selecting a desired RF video channel and for converting a selected RF video carrier to a video carrier at a predetermined IF video carrier frequency, said tuner means including a voltage-controlled local oscillator; an IF stage coupled to said tuner means including an acoustic surface wave IF bandpass filter for shaping the frequency response characteristic of the IF stage, said acoustic surface wave If bandpass filter having a first thermal response characteristic; video demodulating means for demodulating an IF signal from said IF stage to produce a video signal; and control means responsive to an IF signal from said IF stage and comprising an AFC loop including said tuner means, said control means including an acoustic surface wave discriminator having a center frequency, said discriminator generating a control signal for adjusting the tuning of said voltage-controlled local oscillator to cause said system to automatically seek a frequency alignment between said IF video carrier frequency and said center frequency, said acoustic surface wave discriminator having a second thermal response characteristic, the thermal response characteristics of said bandpass filter and said discriminator being similar; and means exposing said bandpass filter and said discriminator to similar ambient temperatures to cause temperature tracking of the frequency characteristics of said IF stage and of said AFC loop.

Claim 8

In a television receiver, the combination comprising: tuner means for selecting a desired RF video channel and for converting a selected RF video carrier to a carrier at a predetermined IF video carrier frequency; an IF stage coupled to said tuner means; and means including a synchronous detector for demodulating said IF video carrier, and a reference oscillator for generating a reference signal precisely at said predetermined IF video carrier frequency for heterodyning with said IF video carrier from said IF stage, said reference oscillator being characterized by a piezoelectric substrate having a smooth surface upon which is a single surface wave filter transducer with a pair of interdigitated electrodes having an impedance characteristic which is highly frequency selective at said IF video carrier frequency for establishing the frequency of oscillation of said oscillator.

Claim 9

In a television receiver, the combination comprising: tuner means for selecting a desired RF video channel and for converting a selected RF video carrier to a carrier at a predetermined IF video carrier frequency; an IF stage coupled to said tuner means; and means including a synchronous detector for demodulating said IF video carrier, and a reference oscillator for generating a reference signal precisely at said predetermined IF video carrier frequency for heterodyning with said IF video carrier from said IF stage, said reference oscillator being characterized by a piezoelectric substrate having a smooth surface upon which is a single surface wave filter transducer with a pair of interdigitated electrodes having an impedance characteristic which is highly frequency selective at said IF video carrier frequency for establishing the frequency of oscillation of said oscillator.

Claim 10

In a television receiver, the combination comprising: tuner means for selecting a desired video channel and for converting a selected RF video caRrier to a carrier at a predetermined IF video carrier frequency, said tuner means including a local oscillator controllable in frequency by means of a voltage control signal; an IF stage coupled to said tuner means; a synchronous detector for demodulating said IF video carrier, including a reference oscillator for generating a reference signal precisely at said predetermined IF video carrier frequency for heterodyning with said IF video carrier from said IF stage; and an automatic frequency and phase control loop including comparator means receiving an IF video carrier signal from said IF stage and a signal from said reference oscillator for generating a control signal representing any difference in frequency or phase between the compared signals, said loop including means for coupling said control signal back to said local oscillator in said tuner means so as to adjust the frequency and phase of said IF video carrier frequency toward synchronism with said reference oscillator at a predetermined phase displacement, said reference oscillator being characterized by a piezoelectric substrate having a smooth surface upon which is a single acoustic surface wave filter transducer with a pair of interdigitated electrodes having an impedance characteristic which is highly frequency selective at said IF video carrier frequency for establishing the frequency of oscillation of said reference oscillator.

Claim 11

In a television receiver, the combination comprising: tuner means for selecting a desired video channel and for converting a selected RF video caRrier to a carrier at a predetermined IF video carrier frequency, said tuner means including a local oscillator controllable in frequency by means of a voltage control signal; an IF stage coupled to said tuner means; a synchronous detector for demodulating said IF video carrier, including a reference oscillator for generating a reference signal precisely at said predetermined IF video carrier frequency for heterodyning with said IF video carrier from said IF stage; and an automatic frequency and phase control loop including comparator means receiving an IF video carrier signal from said IF stage and a signal from said reference oscillator for generating a control signal representing any difference in frequency or phase between the compared signals, said loop including means for coupling said control signal back to said local oscillator in said tuner means so as to adjust the frequency and phase of said IF video carrier frequency toward synchronism with said reference oscillator at a predetermined phase displacement, said reference oscillator being characterized by a piezoelectric substrate having a smooth surface upon which is a single acoustic surface wave filter transducer with a pair of interdigitated electrodes having an impedance characteristic which is highly frequency selective at said IF video carrier frequency for establishing the frequency of oscillation of said reference oscillator.

Claim 12

In a television receiver, the combination comprising: tuner means for selecting a desired video channel and for converting a selected RF video carrier to a carrier at a predetermined IF video carrier frequency, said tuner means including a voltage-controllable local oscillator; an IF stage coupled to said tuner means, including an acoustic surface wave bandpass filter comprising an appropriately poled, thermally homogeneous piezoelectric substrate means on which is disposed in spaced relationship input surface wave transducer means and output surface wave transducer means; a synchronous detector for demodulating said IF video carrier including a reference oscillator for generating a reference signal precisely at said predetermined IF video carrier frequency for heterodyning with said IF video carrier from said IF stage; and an automatic frequency and phase control loop including a comparator for receiving an IF video carrier signal from said IF stage and a signal from said reference oscillator for generating a control signal representing any difference in frequency or phase between the compared signals, said loop including means for coupling said control signal back to said local oscillator in said tuner means so as to adjust the frequency and phase of said IF video carrier frequency toward synchronism with said reference oscillator at a predetermined phase displacement, said reference oscillator being characterized by including frequency selective acoustic surface wave filter means having a driving point impedance characteristic which is highly frequency selective at said IF video carrier frequency for establishing the frequency of oscillation of said oscillator, said filter means including third surface wave transducer means disposed on said piezoelectric substrate means.

Claim 13

In a television receiver, the combination comprising: tuner means for selecting a desired video channel and for converting a selected RF video carrier to a carrier at a predetermined IF video carrier frequency, said tuner means including a voltage-controllable local oscillator; an IF stage coupled to said tuner means, including an acoustic surface wave bandpass filter comprising an appropriately poled, thermally homogeneous piezoelectric substrate means on which is disposed in spaced relationship input surface wave transducer means and output surface wave transducer means; a synchronous detector for demodulating said IF video carrier including a reference oscillator for generating a reference signal precisely at said predetermined IF video carrier frequency for heterodyning with said IF video carrier from said IF stage; and an automatic frequency and phase control loop including a comparator for receiving an IF video carrier signal from said IF stage and a signal from said reference oscillator for generating a control signal representing any difference in frequency or phase between the compared signals, said loop including means for coupling said control signal back to said local oscillator in said tuner means so as to adjust the frequency and phase of said IF video carrier frequency toward synchronism with said reference oscillator at a predetermined phase displacement, said reference oscillator being characterized by including frequency selective acoustic surface wave filter means having a driving point impedance characteristic which is highly frequency selective at said IF video carrier frequency for establishing the frequency of oscillation of said oscillator, said filter means including third surface wave transducer means disposed on said piezoelectric substrate means.

Claim 14

The apparatus defined by claim 8 wherein said input, output and third transducer means are disposed upon a common surface of said substrate means.

Claim 15

For use in a video signal processing system of a television receiver having an IF signal processing stage and a synchronous video detection circuit having a reference oscillator, a composite surface wave filter device comprising: thermally homogeneous piezoelectric substrate means propagative of acoustic surface waves; input and output surface wave transducer means adapted for connection in said IF signal processing stage and disposed in spaced relationship on a surface of said substrate means for respectively launching and receiving surface waves on saiD substrate surface, said input and output transducer means being configured such as to impress upon an electrical output signal developed by said output transducer means a predetermined IF bandpass filtering characteristic; and third electro-acoustic transducer means on a surface of said substrate means and adapted for connection in said reference oscillator in said synchronous video detection circuit so as to establish the frequency of oscillation thereof, said third transducer means being configured and arranged such that the impedance characteristic thereof if highly frequency selective at a predetermined IF video carrier frequency.

Claim 16

For use in a video signal processing system of a television receiver having an IF signal processing stage and a synchronous video detection circuit having a reference oscillator, a composite surface wave filter device comprising: thermally homogeneous piezoelectric substrate means propagative of acoustic surface waves; input and output surface wave transducer means adapted for connection in said IF signal processing stage and disposed in spaced relationship on a surface of said substrate means for respectively launching and receiving surface waves on saiD substrate surface, said input and output transducer means being configured such as to impress upon an electrical output signal developed by said output transducer means a predetermined IF bandpass filtering characteristic; and third electro-acoustic transducer means on a surface of said substrate means and adapted for connection in said reference oscillator in said synchronous video detection circuit so as to establish the frequency of oscillation thereof, said third transducer means being configured and arranged such that the impedance characteristic thereof if highly frequency selective at a predetermined IF video carrier frequency.

Claim 17

The apparatus defined by claim 10 wherein said input, output and third transducer means are located on separate, thermally coupled piezoelectric substrates.