Coplanar 4-bit HEMT phase shifters for 94 GHz phased array radar systems

Coplanar 4-bit phase shifters for W-band operation at 94 GHz have been developed using PM-HEMTs as switching elements. The phase shifter MMIC uses double stub loaded lines and branch line couplers. A two-stage variable gain cascode amplifier was integrated with the phase shifter. This combination has insertion gain of 2-8 dB and occupies an area of 1.5/spl times/4 mm/sup 2/. A redesigned version of the phase shifter occupies 1/spl times/2.5 mm/sup 2/ chip area, and has a standard phase deviation of less than 2.1/spl deg/ for all phase states.