A signal modulation apparatus includes: a reference signal generator that generates an analog reference signal by removing at least one harmonic signal component corresponding to at least one higher-order frequency from a triangular wave signal; a modulation signal generator that performs pulse width modulation for comparing the analog reference signal with an analog input signal, thereby to generate an analog modulation signal; a digital signal converter that converts the analog modulation signal to a digital output signal; and a nonlinear converter that performs nonlinear conversion corresponding to waveform conversion for converting the triangular wave signal to the analog reference signal, on the digital output signal or the analog input signal.

A method and device for synthesizing binary waveforms, wherein the initial analogue waveform is first converted into the segments with discrete levels, then each said discrete level section is in turn converted into a binary pulse of the same time duration as the given segment, and the average value of the generated pulse is proportional to the average value of the given initial waveform over the time duration of the given segment.