Design and analysis of a bulk micromachined distributed digital microwave phase shifter on glass substrate

In this paper, the design and analysis of a bulk micromachined distributed digital microwave phase shifter is introduced. This device, with nonlinear delay line architecture, utilizes 12 butterfly-like microbridges on glass substrates as loading varactors to deliver true time delay performance. The loading capacitance switches between two values, with the pull-in and deformation of the microbridges, introducing phase shift proportional to frequency. Microwave performance is analysed with finite element method. The phase shift anticipation conforms to the test result, which is over 180deg at 20 GHz, with a return loss less than -10dB ( 5 ~ 23GHz). The tested insertion loss is 3.8 ~ 7dB, due to thin metalization of CPW. The microbridge design not only eliminates thermal mismatch between all-metal bridge and dielectric substrate and ensures stability under high temperature, but also guarantees much lower creeping and fatigue probabilities than metal bridges