Amplitude modulator forms two phase-shifted pulse trains and combines them

A system for impressing a modulating information signal of varying voltage amplitude upon a carrier frequency signal, comprising:

• means for producing a bipolar signal having the carrier frequency, each half-cycle of said bipolar signal being 180.degree. electrical degrees wide and of unvarying voltage amplitude;
• filter means for extracting from said bipolar signal the sinusoidal waveshape fundamental signal component thereof having said carrier frequency, each half-cycle of said fundamental signal component being 180 electrical degrees wide and of a constant peak voltage amplitude;
• voltage amplitude comparison means responsive to inputs of said modulating signal and said fundamental signal component for generating complementary trains of unipolar rectangular pulses, the leading and trailing edges of each pulse and its complement respectively occurring an equal number of electrical degrees before and after the electrical angle at which each half-cycle of said fundamental signal component reaches its peak voltage amplitude, the width of said unipolar pulses in electrical degrees being variable and each having a width corresponding to the length of time in a positive half-cycle of said fundamental signal component that the voltage amplitude of said information signal is exceeded by instantaneous voltage amplitude values of said fundamental signal component;
• first triggerable pulse generating means coupled to the output of said comparison means for being triggered thereby to generate a first train of unipolar rectangular pulses 180 electrical degrees wide at the carrier frequency, each 180.degree. wide pulse of said first train starting simultaneously with the starting of a respective variable width unipolar rectangular pulse generated by said voltage amplitude comparison means;
• second triggerable pulse generating means coupled to the output of said comparison means for being triggered thereby to generate a second train of unipolar rectangular pulses 180 electrical degrees wide at the carrier frequency, each 180.degree. wide pulse of said second train starting simultaneously with the ending of a respective variable width unipolar rectangular pulse generated by said voltage amplitude comparison means, whereby said first and second trains of 180.degree. wide unipolar rectangular pulses are generated with a phase difference therebetween which varies linearly with the pulse widths of the variable width unipolar rectangular pulses generated by said voltage amplitude comparison means;
• first circuit means connected at its input to the output of said first triggerable means for extracting from said first train of 180.degree. wide rectangular pulses the sinusoidal waveshape fundamental signal component thereof;
• second circuit means connected at its input to the output of said second triggerable means for extracting from said second train of 180.degree. wide rectangular pulses the sinusoidal waveshape fundamental signal component thereof, the fundamental signal components extracted respectively by said first and second circuit means having the same variable phase difference therebetween as have said first and second trains of 180.degree. wide rectangular pulses;
• and
• means for combining the two fundamental signal components to form an amplitude modulated carrier frequency voltage whose modulation, determined by the phase difference of said fundamental signal components, is a linear function of the varying voltage amplitude of said modulating information signal.

A time and event directed logical processing method for impressing an information signal on a carrier signal, comprising the steps of:

• producing unipolar pulses and their complements with durations coincident with time intervals during which the instantaneous amplitude of a sinusoidal carrier frequency signal is greater than the information signal amplitude;
• timing logical processing of said pulses and their complements in relation to events defined in relation to alternations at the carrier frequency;
• forming in continuous response to the logically processed pulses and their complements, respective pairs of trains of overlapping 180.degree. wide pulses, one train pair defining the first of two resultant signal waveforms and the other train pair defining the second of two resultant signal waveforms;
• extracting the fundamental signal component from each of said resultant signal waveforms to provide respective variably phase-displaced sinusoidal waveforms of said carrier frequency;
• and,
• vectorially adding the waveforms resulting from said extracting step, whereby as the level of the information signal is varied from 0 to the maximum of the sinusoidal carrier frequency signal, an amplitude modulated carrier frequency wave is formed whose envelope linearly conforms with the varying level of said information signal.