The loop-gain modulator: A new class of linear amplitude modulators

A new type of class A modulator is introduced. This circuit, called the loop-gain modulator, exhibits a high degree of modulation linearity even for an index of modulation approaching unity. The concept is based on modifying the loop-gain of an oscillator with the modulating voltage. An analysis is done for the RC phase shift oscillator, although the method can be used with any oscillator. Experimental results that verify this analysis are reported.