Randomized carrier PWM with exponential frequency mapping

Pulse width modulation (PWM) and sigma delta modulation (SDM) have been used in several high linearity, high accuracy power delivery applications such as DC-DC power converters, audio and RF power amplifiers as well as in data converters. In this paper, we present a particular class of carrier frequency modulated PWM (CFMPWM), which spreads the tonal content of regular PWM uniformly in frequency and reduces the baseband noise with respect to SDM by up to 15 dB. The new modulation scheme preserves at the same time the high efficiency properties of PWM. An approximate method to estimate the spectrum of CFMPWM signals with both deterministic and random modulation is also presented. Simulation results and experimental data are reported to analyze the spectral spreading properties of the proposed CFMPWM scheme