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This paper presents a robust heterodyne mode of operation for the envelope load-pull system. Extensive performance evaluation and verification demonstrate the reliable, flexible and accurate nature of the system. The new system was compared with the active open-loop load pull, with the new system standing out as having superior performance in terms of measurement throughput, thereby improving the yield and turn-around in the design of power amplifiers. Finally, measurements on commercially available microwave transistor devices show some of the immediate recognized application areas of the developed system.

We have developed a technology to fabricate pseudomorphic 0.3 µ m gatelength modulation doped field-effect transistors (MODFETs) having a breakdown voltage up to 20 Volts. This technology uses molecular beam epitaxy (MBE) to grow the InGaAs/AlGaAs/GaAs heterostructure with two pulse doping layers on 3 inch semiisolating GaAs wafers. A mix and match lithography was applied using an i-line stepper and an electron beam direct write process to define the mushroom shaped gates (T-gates). The breakdown enhancement is achieved by a self aligned selective double dry etched gate recess using AlGaAs etch stop layers. We investigated the heterostructure doping and the influence of the gate recess process to the device performance.