Efficiency Power Amplifiers
||Jian Xu, Bob York
||YiFeng Wu, WiTech LLC
This work is aimed at developing high power amplifier modules
for multi-octave operation and high efficiency. Initial efforts have focused on the
use of travelling- wave amplifier (TWA) concepts. TWAs offer wide bandwidth by
incorporating the device Cgs into a synthetic transmission line. Ordinarily the
outputs are similarly combined into a synthetic line, but this results in low efficiency
due to the excitation of a backward wave. We have modified the TWA to include an
efficient broadband output combiner circuit. We also use capacitive division at the
input of the devices to increase the bandwidth and equalize the drive levels.
Prototypes have demonstarted the idea using flip-chip mounting of GaAs FETs onto a
thermally managed AlN substrate.
|Pictured at right: (top) Modified capacitive-division TWA
using output combiner; (middle) picture of completed circuit using commercial GaAs FETs;
(bottom) Measured performance and comparison to theory.
GaN Devices and Circuits