Continental Electronics Corporation

Continental Electronics Mfg. Co.

George D Hanna

A system and method for amplitude modulating a carrier signal with an audio or other information input signal relies on multivibrators and comparators initiating a logic controlled processing technique for providing two sinusoids, each a fundamental frequency waveform, the two having a mutual phase relationship defined by intermediate processing steps such that they differ in phase from 0 to 180 electrical degrees. The comparators output first resultant pulses when the carrier signal is greater than the amplitude of the audio or other information input signal. The first resultant pulses are input to a logic processing network to trigger multivibrators which output overlapping 180.degree. wide pulses, respective phase shifted resultant signal waveforms being formed from the respective comparator outputs. In the output stage, the respective resultant waveforms are amplified and filtered to form the two sinusoids which are added vectorially to form an amplitude modulated output signal which varies linearly with the audio or information input signal.

Amplitude modulator forms two phase-shifted pulse trains and combines

A method and apparatus for amplitude modulating a carrier signal with an audio or information input signal utilizes an arcsine generator to cause the envelope of the carrier to follow the input signal. The invention stems from the realization that if rectangular pulses of bipolar amplitude are symmetrically centered about 0 and .pi. radians of the carrier signal, the harmonic content can be expressed as a function of the angle of the rectangular pulses. This concept is realized by producing two opposite phase carrier signals which are compared with the modulation input signal to form two opposite phase rectangular pulse signals whose pulse widths are a function of the modulation input signal. Alternate phase pulses are extracted from these two rectangular pulse signals by two NOR gates, and the extracted pulses are combined and filtered to obtain an amplitude modulated output signal.

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Dallas, TX, United States of America

George D Hanna