Amplitude demodulator using a phase locked loop

Claim 1

An amplitude demodulator for an amplitude modulated signal having a predetermiNed range of modulating frequencies using a phase locked loop comprising, a semiconductor body, phase locked loop means including phase comparator means receiving the amplitude modulated signal and providing an output signal, filtering means coupled to the phase comparator means, a voltage controlled oscillator coupled between the phase comparator means and the filtering means, said voltage controlled oscillator providing an output signal, said phase comparator means comparing the phase of the output signal of said voltage controlled oscillator with said amplitude modulated signal to provide a difference signal indicative of any phase difference, said filtering means filtering said difference signal and coupling said filtered difference signal to said voltage controlled oscillator whose output signal is controlled thereby, means for multiplying in phase components of said output signal of said voltage controlled oscillator and said amplitude modulated signal whereby an output signal is produced by said multiplying means similar to he modulation signal of said amplitude modulated signal, and filtering means coupled to said multiplying means for filtering out substantially all frequencies outside of said range of said modulating frequencies, said demodulator being formed exclusively of noninductive type circuit elements, substantially all of said circuit elements being formed in said semiconductor body, said demodulator being capable of assimilating tolerance variations in said circuit elements of greater than 10 percent.