RF communications with spectral efficiency utilizes complex modulation schemes that
require amplifier linearity [1]. As amplifier operating frequency moves into the millimeter
wave (mm-wave) range, the power added efficiency becomes also important to save the
system prime power. As for 5G applications, high efficiency and linearity of amplifiers are
required to support complex waveforms with high peak-to-average ratio (PAPR) and large
instantaneous bandwidth.
We report the first demonstration of graded-channel GaN HEMTs operating in the
millimeter-wave frequency range. At 30 GHz, these graded-channel GaN HEMTs
demonstrated excellent PAE of 65% at associated power density of 3 W/mm. The measured
PAE and output power density shows great improvement over other mm-wave T-gated
AlGaN/GaN HEMT devices. Under two-tone linearity characterization at 30 GHz, PAE of
about 50% was demonstrated with C/IM3 of 30 dBc, which is very promising for mmwave
linear and efficient amplifiers without digital pre-distortion.
This material is based upon work supported by the DARPA under contract number
FA8650-18-C-7802. The views expressed are those of the author and do not reflect the
official policy or position of the DARPA or the U.S. Government. Any opinions, findings
and conclusions or recommendations expressed in this material are those of the author(s)
and do not necessarily reflect the views of the U.S. Government.