Transmission of signals through analog channels using adaptive f

Details Transmission of signals through analog channels using adaptive f Transmission of signals through analog channels using adaptive f

1987-06-10

1990-03-06

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358167, 358 23, 455 44, H04B 110, H04B 1500, H04N 521, H04N 540

Patent

active

049070878

ABSTRACT:
Improved effifiency of frequency-modulated (FM) transmission of signals through analog channels, i.e., achievement of a higher bandwidth and/or signal-to-noise ratio (SNR) in the received signal for a given channel bandwidth and channel carrier-to-noise ratio (CNR), is accomplished by adaptive adjustment of the modulation index in such a manner that the spectrum of the channel signal more nearly occupies the entire channel more of the time than it would otherwise. Data is transmitted, along with the signal, to enable the receiver to calculate the modulation index at each instant so that the signal can be properly demodulated. The invention has application to FM transmission of signals representing visual image or other information, such as sound, for which human perception of noise is greatest in areas of low amplitude and/or frequency and reduced in and immediately adjacent to areas of high amplitude and/or frequency.

REFERENCES:
patent: 4007483 (1977-02-01), Pham van Cang
patent: 4607285 (1986-08-01), Hirota
patent: 4618893 (1986-10-01), Hirota
"A Two-Channel Picture Coding System II: Adaptive Companding and Color Coding," IEEE Transactions on Communications, vol. COM-29, No. 12, Dec. 1981, by W. F. Schreiber and R. R. Buckley.

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