Circuitry for reducing demodulation phase error as for an automa

Details Circuitry for reducing demodulation phase error as for an automa Circuitry for reducing demodulation phase error as for an automa

1986-05-29

1987-08-11

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358905, 358 35, H04N 521

Patent

active

046865691

ABSTRACT:
An automatic deghosting system synchronously demodulates IF television signals to generate baseband composite video signals. A strong RF ghost signal having a carrier phase that differs from that of the desired signal may cause demodulation phase errors, causing quadrature distortion in the baseband video signals. The circuitry shown in this disclosure synchronously demodulates the quadrature component of the IF television signals and develops a signal proportional to the difference between the values of the baseband quadrature signal immediately before and immediately after the leading edge of the vertical sync pulse. This signal, which is proportional to the demodulation phase error, is used to control a phase locked loop that regenerates the in-phase and quadrature carrier signals used by the synchronous demodulators to substantially eliminate any demodulation phase error.

REFERENCES:
patent: 4047224 (1977-09-01), Yamaguti
patent: 4261016 (1981-04-01), Hongu
patent: 4285006 (1981-08-01), Kurahashi et al.
patent: 4374400 (1983-02-01), Holmes
patent: 4584652 (1986-04-01), Sturza et al.
Thedick, H. "Adaptive Multipath Equalization for T.V. Broadcasting", IEEE Trans. on Consumer Electronics, May 1977, pp. 175-181.

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