Direct QAM modulation using a class E amplifier

A class E amplifier´s ability to accurately represent abrupt phase and amplitude transitions of the input signal at its output port is investigated to examine its suitability for digital phase-modulated transmission schemes, e.g. GMSK, QPSK, nQAM. Based on these results, a novel 8QAM transmitter topology is suggested. The novel topologies promise low complexity, are suitahle for mass production, and provide high DC-to-RF efficiency. The feasibility of these topologies is proven by measurement. It is shown that 270 khps GMSK PN15 pseudorandom signal can he amplised at 79% PAE with only 0.5° phase error, while direct 8QAM can he achieved with 11.2 dB peak gain and 3.6° peak phase error.