Demodulator circuit for television multi-channel

Details Demodulator circuit for television multi-channel Demodulator circuit for television multi-channel

1990-02-01

1990-08-28

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358143, 358198, H04N 704

Patent

active

049530216

ABSTRACT:
A multi-channel sound signal received and detected in a TV receiver includes a main channel signal comprising a stereo sum (L+R) signal, a stereo pilot signal having a frequency of f.sub.H equal to the frequency of a horizontal synchronizing signal, and a sub-channel signal obtained by DSB modulation of a sub-carrier having a frequency of 2f.sub.H by a stereo difference (L-R) signal. In a TV multi-channel sound signal demodulator circuit, the sub-carrier is reproduced by a PLL circuit in response to the stereo pilot signal, to demodulate the stereo difference (L-R) signal using the sub-carrier. The stereo difference signal thus demodulated includes a 60Hz noise component due to interference between a sound signal and a video signal. However, the noise component is removed by a high-pass filter provided between a sub-channel signal demodulator circuit and a matrix circuit. Thus, right and left stereo signals R and L outputted from the matrix circuit do not include a noise component.

REFERENCES:
patent: 4405944 (1983-09-01), Eiters et al.
patent: 4680793 (1987-07-01), Sugai et al.
patent: 4723287 (1988-02-01), Tobita et al.
Fockens et al., "Intercarrier Buzz Phenomena and Cures", IEEE Transactions on Consumer Electronics, vol. CE-27, #3, pp. 381-393, 8/81.
Television Journal, "Buzz-Beat Interference in Multi-Sound Television Receivers", Murakami et al., vol. 26, No. 6, 1972, pp. 459-467.
NEC, "Decoder System ICs for US Multichannel TV Sound", Fukaya et al., vol. 39, No. 3, 1986, pp. 4-8.

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