Continuous Modes for High Efficiency Design

Network synthesis for high efficiency microwave power amplifier design is a topic with many more constraints imposed upon it than classical filter design. High efficiency designs mandate the correct termination of fundamental and harmonic impedances to generate current and voltage waveforms that have a minimum overlap. Classical network synthesis techniques such as filter prototypes and even advanced techniques such as real frequency synthesis typically only deal with a single frequency band. Add into the mix modulated signals, for which the baseband impedance is just as important, plus the practicalities of physically realizing component values, and the problem can quickly seem intractable. Continuous modes are one tool that the designer can utilize to trade flexibility in the impedance domain, for increases in the voltage waveform peak magnitude. This session aims to highlight how the continuous modes were developed from classical amplifier operating modes (class B, class F, inverse class F etc), and how they can assist the designer in achieving high efficiency over a very wide bandwidth. Some of the drawbacks of continuous mode operation will also be discussed.