Multi-level asynchronous Sigma Delta modulators for wideband switching power amplifiers

Abstract

This work extends the Asynchronous ΣΔ Modulator and its Adaptive version to multi-level modulators, targeting wideband high-efficiency switching power amplifiers. The performance of these modulators is compared with the multi-level Pulse Width Modulator, the most common modulator in multilevel switching power amplifiers. Behavioural model simulation results show that, unlike the multi-level PWM (which can only be used at high switching frequencies), the Asynchronous ΣΔ Modulators can also be used at average switching frequencies close to the signal bandwidth. At high switching frequencies, the performance of all the modulators is similar. The Asynchronous ΣΔ Modulators have further and more important advantages, such as high PSRR (even at the input signal frequency), the ability of handling non-regular distributed voltage levels, or a low ratio between the average switching frequency and the maximum instantaneous switching frequency.