It is necessary for microwave monolithic integrated circuits (MMICs) to avoid performance variations due to non-uniformity in circuit parameters, as well as to improve uniformity for semiconductor wafers. In this paper, resistive elements, resulting in low circuit Q, were introduced into a microwave GaAs monolithic amplifier, to make it insensitive to the circuit parameter variations. Also, an ion implantation technique and the Closely Spaced Electrode FET" structure were adopted to improve the uniformity in FET active layers and resistive layers. These brought about good results. The developed GaAs monolithic amplifier is a 3-stage amplifier. The load for each FET is mainly formed by a resistance and the next stage FET input capacitance, except for the final stage FET. Meander and spiral transmission lines are used for peaking. The developed GaAs monolithic amplifier provides more than 7.5-dB gain from below 100 MHz to 8.5 GHz without any circuit trimming. The amplifier also has low input and output VSWR. Cascading two amplifier chips, more than 14-dB gain could be achieved from below 100 MHz to 8.7 GHz. Both calculated and measured characteristics for the amplifier are comparatively in good agreement. Also, amplifier performance variations due to the circuit parameter variations are discussed comparatively both for resistive matching network and conventional loss-less matching networks.

Making good use of low impedance and short wavelength characteristics of high dielectric substrate whose dielectric constant (εr) is 39 to 139, and advanced microwave integrated circuit (MIC) technology has been proposed to realize low-cost highly-reliable and small size UHF power amplifiers. Numerical calculation of single and parallel-coupled microstrip parameters on the high-dielectric constant substrate has been presented at first. Then the thick film technique application possibilities are discussed for high-dielectric substrate MICs, which is more suited for low price and mass production than conventional thin film technique. Based on theoretical and experimental estimation results, an amplifier with εr39 substrate has been developed to replace TWTs in television transposers, which provides a rated output peak power of 32 W with low distortion characteristics over the 650770 MHz frequency range. A compact 500 MHz-band 12 W class-C amplifier has also been developed successfully with use of εr139 substrate.