engleski

Switch-mode radiofrequency amplifiers with complementary filters

This work introduces a novel approach in using constant resistance networks, specially complementary filters in a diplexer configuration, on the output of a radio-frequency switch-mode modulator. Theory concepts and design for the filters, with a crossover frequency of 800 MHz and 2.5GHz, are considered and the filters were assembled and measured. Based on the measurements and simulations we concluded that switch-mode RF power amplifiers terminated with complementary filters exhibit higher and more consistent drain efficiency than when terminated with only a low-pass filter. Despite increasing and stabilizing the drain efficiency, the filters present a slightly more stringent assembly procedure in comparison to the widely used low-pass filters due to the fact that the s11 parameter, which we want to be minimal as possible, falls off due to phase mismatch between the low-pass and high-pass section. We used time domain reflectometry(TDR) to evaluate the quality of the filter’s assembly. Using TDR simulations and measurements we identified the discontinuities that lower the performance of the complementary filters.

switch-mode power amplifiers ; radiofrequency power amplifiers ; complementary filters ; reflectionless filters

Master's Thesis No. 1822