Abstract: When conducting design of RF high power amplifier (HPA), the broadened microstrip λ/4 bias line for high DC current decreases the performance of the HPA. In this article, a thickened microstrip line is proposed to design the λ/4 drain bias circuit for HPA and is applied to a power amplifier for a miniaturized satellite transmitter. Measurement results showed that thickened bias line is feasible and useful for increasing HPA’s performance.

Key words: Power amplifier, Bias circuit, Small signal S parameter, Power added efficiency (PAE)