ABSTRACT*
Design of S-band and X-band Internally-Matched Power Amplifiers
using GaN HEMTs
Hyun-Seok Kang
Department of Radio Science and Engineering, Graduate School,
Chungnam National University
Daejeon, Korea

(Supervised by Professor Dong-Wook Kim)
In this thesis, S-band and X-band internally-matched power
amplifiers were designed and fabricated using bare GaN HEMTs. A 300
W power amplifier for the LTE band 7 applications was designed
using the Cree’s GaN HEMT, CGHV40320D. We performed fundamental
and harmonic load-pull simulations using the nonlinear transistor model
which is provided by Wolfspeed, a Cree company. The harmonic impedance
tuning was done using λ/4 open stubs and stepwise transmission lines
inside package. The fabricated power amplifier showed a linear gain of 17
dB or more from 2.62 GHz to 2.69 GHz. Its saturated output power and
drain efficiency were 257∼323 W and 67∼71%, respectively. It also had the
drain efficiency of 42∼49% and the ACLR of 30 dBc or more at the
condition of 79 W LTE input power. The fabricated power amplifier could
be used for the base stations of LTE communications.
An X-band internally-matched power amplifier was also designed and
fabricated using the bare GaN HEMT which was developed at Electronics
and Telecommunications Research Institute, and its optimum input/output
impedance was obtained through source-pull and load-pull measurements
using pre-matched impedance transformation networks. Based the
estimated optimum input/output impedance, the power amplifier that was
fabricated on a Duroid 6010LM substrate using a thick film process had an
output power of 47∼47.46 dBm and a power-added efficiency
(PAE) of more than 36% from 9.0 GHz to 9.5 GHz. Compared
with the recently published power amplifiers with similar output
power performance at X-band frequency region, the fabricated
GaN internally-matched power amplifier showed a better PAE.
The fabricated power amplifier could be used in the X-band
radar systems and other wireless systems requiring a high
output power