Abstract
This paper proposes signal phase shifters using operations of pulse width modulation (PWM), that a sinusoidal wave and a triangular wave can be arbitrary shifted. From the use of D.C. source, their characteristics are available for generating high power signals of which the phase is varied continuously. In principles, they especially have effectiveness in Ultra Low Frequency regions. Frequency spectrum of this PWM wave can be analysized theoretically by multiple Fourier series expansion and experimental values agree well with their theoretical ones. We examine methods to improve their frequency spectrum distribution and propose a improved method that switches the modulation. Experimental results verify it. We can get precise output signal wave forms by making use of a microprocessor for the PWM modulation. Circuit compositions to realize it are easy because of logic circuits. It may be able to integrate. The PWM sinusoidal phase shifter can be utilized as a PWM sinusoidal inverter with a function of phase shifting and the PWM triangular phase shifter may be applied to a wave form generator using triangular polynomial expression.
