Design considerations for the dual-fed distributed power amplifier

The dual-fed distributed amplifier is a variation of the conventional single-fed distributed amplifier whereby the input signal is fed to both ends of the input line using a hybrid, and signals appearing at both ends of the output line are combined using another hybrid. Such a configuration allows utilisation of output power in the backward as well as forward waves. Much of the previous work in the literature only considered small-signal analysis and small electrical spacing between FETs, and did not lend insight into the operational behaviour. This paper therefore considers the development of a design method for the dual-fed distributed power amplifier with large electrical spacing. The simulations demonstrate optimum loadlines are achieved for all FETs and that all FET output power is utilised