In this paper, we have designed and fabricated pre-matched and bus type of gates and, then, carried out analyses of input return loss (IRL) and phase differences for millimeter waves. From analyses of phase differences of the excited signal at each gate electrode by momentum simulations, the PHEMT's with pre-matched gate have much smaller phase difference than ones with bus type gate. The IRL differences between the pre-matched and bus type gates with unit gate widths of 25, 40 and 50μm are 0.62±0.04, 0.52±0.08 and 0.49±0.05 dB, respectively. The overall improvements of IRL's for the pre-matched gate compared with bus type is 0.54±0.11 dB at 30 GHz. Also, the overall improvement of S{sub}21 gain for the pre-matched gate compared with bus type gate is 0.88 dB at 30GHz.
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