A novel dc-50 GHz MMIC variable attenuator

Design, fabrication and performance of a newly developed novel DC-50 GHz MMIC variable attenuator with multi-function and low inserted phase shift are presented. This attenuator MMIC was fabricated by using Nanjing Electronic Devices Institute (NEDI) ion-implanted GaAs MMIC foundry process. Based on special design of both the series MESFET and shunt MESFET control feeders, the MMIC has possessed the feature of excellent VSWR character even without the use of DC reference circuit, which is commonly adopted by various MMIC attenuators. Also, phase compensation technique was used in MMIC design to reduce inserted phase shift. On-wafer measurement results of the developed MMIC chips in DC-50 GHz band are minimum attenuation <3.7 dB; maximum attenuation >38±5 dB; both input/output VSWR<1.5 at minimum attenuation and <2.2 at maximum attenuation; low inserted phase shift attenuation ratio of <1.2°/dB. The chip size is 2.33 mm×0.68 mm×0.1 mm. To the best of our knowledge, this is the first reported MMIC voltage control variable attenuator with low inserted phase shift over DC-50 GHz in the world.