Motorola Corporation

Melvin A Schechtman

Thomas J Walczak

Michael E Rebeschini

Ronald H Cieslak

A modulation limiter that eliminates over-deviation otherwise caused by asymmetrical modulation signals in a frequency modulated (FM) transmitter. The output signal from a conventional modulation clipper is integrated, multiplied by a gain constant, and subtracted from the input, which causes the clipper output to have zero average and a high-pass frequency response with a time constant determined by the feedback gain. The zero average value allows the clipped modulation signal to be coupled to a modulator without over-deviation caused by shifts in the average value of the clipped signal, and the high-pass response can be used to give the modulation signal pre-emphasis.

Instantaneous deviation limiter with pre-emphasis and zero average value

An improved analog CMOS comparator circuit is described. The improved circuit incorporates an additional CMOS device in the output stage of a conventional differential comparator. The additional device compensates for current imbalances which occur at relatively high common mode voltages thus allowing the improved comparator to operate over a wider range of common mode input voltages.

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Schaumburg, IL, United States of America

Melvin A Schechtman