Description:
A spatial power combining system can put out very
high power efficiently. By integrating a huge number of amplifiers, it
remains its high power capability and low the phase noise of a single
amplifier. In particular, the tray structure and the
waveguide environment of the combiner system provides the broadband
characteristic, excellent thermal management, and graceful
degradation.
The concept has been proved in our X-band Power
Combiner (by N.S. Cheng), which has an output power up to 150 watts
with 10dB of power gain. The work is extended to a higher
frequency band (k-band).
The k-band system is built in an oversized waveguide
environment (multi-modes), with monolithic circuit design using
flip-chip bonding for the active devices to reduce the use of
bond-wires and hence improve the efficiency. The waveguide
environment operates in the dominant TE10 mode with TE20 mode being
sufficiently suppressed (symmetrical loading). Each antenna is then
essentially a waveguide-finline-CPW transformer that couples energy
from the wave-guide mode to a set of power amplifiers.
A
passive combining system is built for estimating the overall combining
efficiency. This is characterized by a 6x4 array (6 trays with 4
antennas on each). 75% combining efficiency and <-15dB reflection
from 18GHz~22GHz has been achieved. A preliminary result
using the one stage amplifiers has been obtained. It delivers
33dBm output power. The power combiner using 2 stage amplifiers
is in progress, so is the one using 1watt MMIC. 
