Abstract
The high millimeter-wave (mmW) frequency range offers new possibilities
for high-resolution imaging and sensing as well as for high data
rate wireless communication systems. The use of power amplifiers
of such systems boosts the performance in terms of operating range
and/or data rate. To date, however, the design of solid-state power
amplifiers at frequencies about 210 GHz suffers from limited transistor
model accuracy, resulting in significant deviation of simulation
and measurement. This causes cost and time consuming re-design iterations,
and it obstructs the possibility of design optimization ultimately
leading to moderate results. For verification of the small-signal
behavior of our in-house large-signal transistor model, S-parametermeasurements
were taken from DC to 220 GHz on pre-matched transistors. The large-signal
behavior of the transistor models was verified by power measurements
at 210 GHz. After model modification, based on process control monitor
(PCM) measurement data, the large-signal model was found to match
the measurements well. A transistor model was designed containing
the statistical information of the PCM data. This allows for non-linear
spread analysis and reliable load-pull simulations for obtaining
the highest available circuit performance. An experimental determination
of the most suitable transistor geometry (i.e. number of gate fingers
and gate width) and transistor bias was taken on 100 nm gate length
metamorphic high electron mobility transistor (mHEMT) transistors.
The most suitable combination of number of fingers, gate width and
bias for obtaining maximum gain, maximum output power, and maximum
power added efficiency (PAE) at a given frequency was determined.
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