We have fabricated a 12 GHz-band monolithic microwave integrated circuit amplifier of which the noise level has been reduced down to 1.18-1.35 dB in the frequency range from 11.7 GHz to 12.7 GHz. The excellent characteristics come from the use of low-gate-resistance, low-equivalent-noise-resistance HEMT's which were obtained by using T-getes, and a hi-lo doping profile in an AlGaAs layer.

A 12-GHz-band GaAs monolithic dual-gate FET mixer using a novel circuit configuration has been demonstrated. Adoption of a negative feedback circuit has reduced the output impedance of the mixing dual-gate FET down to 330 Ω, which is approximately one fourth that of conventional dual-gate FET mixers, resulting in good matching to the next state. An experimental MMIC mixer, which included an IF buffer amplifier, exhibited a 3.4-4.2-dB conversion gain with a 11.3-11.6-dB SSB noise figure in the 11.7-12.2-GHz RF band.

Nonlinear operation of an analog frequency divider using a GaAs dual-gate FET has been studied theoretically and experimentally. It is shown that the log-log plot for basic input/output characteristics of the divider shows straight lines in the second, third, and fourth regions adjacent to the first narrow threshold region in the increasing order of input power magnitude. It is suggested from theoretical consideration that universality of the exponent K appearing in the PoutPinK relation holds at least approximately. The value of K in the second region is found to be about 3.0 theoretically and experimentally and is in agreement with the value reported in an earlier paper. The strict but obvious universality of K holds in the third and fourth region with K=1 and 0, respectively.