V-band reflection-type phase shifters using micromachined CPW coupler and RF switches

Abstract

Micromachined reflection-type phase shifters with small size and low loss for V-band communication systems are described. Two- and three-bit reflection type phase shifters were designed, fabricated, and measured. The micromachined air-gap overlay coupler and the direct contact type series switches were employed to implement the phase shift and reduce an insertion loss. The phase shift can be obtained by changing the length of the open-ended stubs using the cascaded MEMS switches. The fabricated two-bit phase shifter has a measured phase shift of 0degrees, 41.5degrees, 84.3degrees, and 128.7degrees with the consecutive actuation of the series MEMS switches. The actuation voltage of the switches is 35 V and the measured switching ON time is 5.1 mus. The average insertion loss of the two-bit phase shifter measured 4.1 dB at 60 GHz and the return losses for all phase shift states are better than 11.7 dB from 50 to 70 GHz. The two-bit phase shifter is small, 1.5 mm x 2.1 mm. By cascading the two-bit phase shifter and a 180degrees phase shifter (one-bit), a three-bit phase shifter is realized, which has a phase shift of 265.5degrees and an average insertion loss of 4.85 dB at 60 GHz. The size of the three-bit phase shifter is 3.2 mm x 2.1 mm.