Table-based PWM for all-digital RF transmitters

In this paper, a novel pulse-width modulator (PWM) for an all-digital PWM transmitter based on switching amplification is presented. In this approach, each symbol is represented by a sequence of pre-computed PWM pulse widths stored in a table that results in reduced error vector magnitude (EVM). A high-resolution pulse former is then used to build the bipolar radio frequency (RF) signal. Simulations and comparisons to other approaches reported in the literature under different oversampling ratios and finite time resolutions are presented. The impact of nonlinearities in the variable duty-cycle generator is also analyzed to demonstrate the robustness of the proposed technique.