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AssigneeMassachusetts Institute of Technology
InventorWilliam F. Schreiber
Estimating the term…
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.
A system for processing a signal representative of information, such as sound or the high frequency content of a visual image, for which human perception of noise is greater in areas of low amplitude and/or frequency and reduced in and immediately adjacent to areas of high amplitude and/or frequency, comprising:
The system of 2 wherein said adaptation means includes means for varying said variable modulation index sufficiently gradually across said image as to make the modulation of said modulation means more linear than that provided by static nonlinear companding.
The system of 1 wherein said adaptation means includes means for varying said variable modulation index sufficiently gradually across said image so as to make the modulation of said variable modulation index more linear than that provided by static nonlinear companding.
Dependencies are inferred from the claim text.