How to reach 100% coding efficiency in multilevel burst-mode RF transmitters

Abstract

Among other goals, multilevel burst-mode radio frequency (RF) transmitters have to achieve two main objectives: high efficiency, and good transmission signal quality. Both of these goals depend, to a large extent, on the driving signal modulator, which can, for example, be a digital pulse-width modulator. However, conventional digital pulse-width modulation (PWM) contains aliasing distortion that prevents achieving satisfying transmission signal quality.In this paper, an aliasing-free digital multilevel PWM method is introduced that allows for achieving good transmission signal quality, while at the same time offering the potential of reaching a coding efficiency of 100%. The mathematical equations for aliasing-free digital PWM are extended in a way that makes them suitable for the use in multilevel burst-mode RF transmitters. It is then shown how the aliasing-free multilevel PWM method can be used to achieve 100% coding efficiency. Simulations demonstrate the performance capabilities of the proposed PWM method.

Coding efficiency of bandlimited PWM based burst-mode RF transmitters

“…This might reduce the PA efficiency. However, the degraded PA efficiency does not necessarily result in a degraded transmitter efficiency because of the higher coding efficiency [6], [7], which is used to evaluate the performance of the PWM encoder and estimate the overall transmitter efficiency. The bandlimitation also has an impact on the signal linearity.…”