Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1976-04-26
1977-11-29
Martin, John C.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358905, 333 72, 310313, 310366, H04N 548
Patent
active
040608336
ABSTRACT:
The intermediate frequency (IF) portion of a television receiver includes a surface acoustic wave (SAW) filter comprising first, second and third transducers mounted on a piezoelectric substrate. Each transducer includes at least two interdigitized comb-shaped conductors. The teeth of the comb-shaped conductors of the first transducer overlap in accordance with a predetermined envelope to define a desired IF response. The first and second transducers are connected to IF circuit portions of the receiver. The third transducer is positioned from the second transducer so that regenerated acoustic signals reflected from the first and third transducers to the second transducer are substantially 180.degree. out of phase at a predetermined frequency. The aperture W.sub.3, i.e., the overlap of the teeth of the comb-shaped elements, of the third transducer is selected with respect to the aperture W.sub.1 of the first transducer and the magnitude of the impedance of the combination of the first transducer and the electrical circuit connected to it so that regenerated acoustic signals reflected from the first and third transducers are substantially equal in magnitude at the predetermined frequency. The regenerated acoustic signals reflected from the first and third transducers are received by the second transducer to develop an electrical output signal substantially free of the influence of ghost-producing multiple reflection signals. The spacing between pairs of interdigitized teeth of the third transducer may be selected so that the center frequency associated with the third transducer is the frequency of the picture carrier, the frequency at which reflected signals are most readily manifested as ghost images.
REFERENCES:
patent: 3596211 (1971-07-01), Dias et al.
patent: 3662293 (1972-05-01), DeVries
patent: 3810257 (1974-05-01), Jones et al.
patent: 3908137 (1975-09-01), Hunsinger
VAN Raalte, "Surface Acoustic-Wave Filter for Television Intermediate Frequencies", RCA Engineer, June-July 1974, vol. 70, No. 1, pp. 15-19.
Electronics Letters, vol. 8, No. 23, Nov. 16, 1972, pp. 553-554.
Emanuel Peter M.
Martin John C.
RCA Corporation
Schaefer Kenneth R.
Whitacre Eugene M.
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