High-frequency limits of millimeter-wave transistors

Estimates of transistor performance at millimeter-wave frequencies are generally based on extrapolation of microwave gain measurements at a gain roll-off of 6 dB per frequency octave. In this paper we show that a complex-conjugate pole pair leads to a 12-dB/octave gain roll-off in the millimeter-wave region. As a result the actual
f_{\max}
of millimeter-wave transistors can be considerably less than that determined using extrapolation of gain measurements.