Waveform synthesis using switching circuits

A method for synthesising a waveform which upon integration will approximate a sinusoid of controllable amplitude comprising:

• generating at least one base square wave having a selected frequency, chopping each square wave once each half cycle with a chopping pulse having a width proportional to the desired amplitude of the sinusoid, generating a control square wave of different fundamental frequency,, and Walsh multiplying said control square wave with the or each chopped square wave to produce a chopped pulse width modulated waveform having a fundamental frequency equal to the difference of the fundamental frequencies of the control and base square waves.

A method for synthesising a waveform which upon integration will approximate a sinusoid of controllable amplitude comprising:

• generating at least one base square wave having a selected frequency, chopping each square wave once each half cycle with a chopping pulse having a width proportional to the desired amplitude of the sinusoid, generatng a control square wave of different fundamental frequency, partially Walsh multiplying said control square wave with each chopped square wave to produce a chopped pulse width modulated waveform having a fundamental frequency equal to the difference of the fundamental frequencies of the control and base square waves, partially Walsh multiplying the complementary forms of said base square waves with the control square wave or the complementary form of the control square wave is partially Walsh multiplied with each base square wave, to produce dual waveforms with the levels of each waveform of a dual being the same for one state only at some time in the switching sequence, and converting these dual waveforms to single bi-directional tri-state waveforms.

A waveform synthesiser for producing a waveform which upon integration will approximate a sinusoidal having an amplitude proportional to frequency comprising:

• a square wave generator producing at least one base square wave, a pule waveform producing a waveform consisting of a fixed duration occurring at least once each square wave half cycle, an inverter fed from said pulse waveform generator, logic circuitry associated with the square wave generator which enables the inverter output for a predetermined fraction of each square wave half cycle, and means for mixing or chopping each square wave with the output from said logic circuitry.

A waveform synthesiser for producing a waveform which upon integration will approximate a sinusoid of controllable amplitude comprising:

• a square wave generator producing at least one base square wave, a variable width chopping pulse generator, producing a pulse the width which determines the amplitude of said sinusoid, logic circuitry associated with the square wave generator which sets the chopping pulse location relative to each half cycle of each square wave, means for mixing or gating each square wave with the chopping pulse, a second square wave generator producing a control square wave, and a Walsh multiplier means corresponding to each phase which is fed by the control square wave and the chopped square wave and provides as an output product the desired waveform in the form of a pulse width modulated waveform having a fundamental frequency equal to the difference of the fundamental frequencies of the control and base square waves.

A waveform synthesiser for producing a waveform which upon integration will approximate a sinusoid of controllable amplitude comprising:

• a square wave generator producing at least one base square wave, a variable width chopping pulse generator producing a pulse the width of which determines the amplitude of said sinusoid, logic circuitry associated with the square wave generator which sets the chopping pulse location relative to each half cycle of each square wave, means for mixing or gating each square wave with the chopping pulse, a second square wave generator producing a conrol square wave, inverting means corresponding to each phase, and two partial Walsh multiplier means corresponding to each phase, one of which is fed by the chopped square wave and the other of which is fed by its complement, both being fed by the control square wave, or alternatively one of which is fed by the control square wave and the other of which is fed by its complement with both being fed by the chopped square wave, and a tri-state static inverter output stage each phase of which is switched by the output from the corresponding two partial Walsh multiplier means.