Design, fabrication, and characterization of RF MEMS variable capacitor phase shifters and prestressed-beam switches

This thesis presents the design, fabrication, and characterization of RF MEMS variable capacitors, loaded-line and reflection-type phase shifters and prestressed-beam switches.; The electromagnetic and mechanical models of the digital-type variable capacitors fabricated by MEMS technology (using MUMPs) are discussed. RF equivalent circuit models for capacitors are derived. A tuning ratio of 3.7:1 has been experimentally demonstrated. The loaded-line phase shifters have been developed using these MEMS variable capacitors. Experimental results have shown a continuously variable phase shift of 40.5° with an insertion loss of 1.1-1.8 dB at 26.5 GHz. A novel design procedure for reflection-type phase shifters using capacitive devices is developed. Following this procedure, a 180° phase shifter for operation at 26.5 GHz has been designed using these MEMS variable-capacitors as phase shifting devices. Experimental results have shown a phase shift of 179.3° at 26.5 GHz, and validate the design procedure.; A novel RF MEMS switch is designed using the concept of prestressed beam. Mechanical design considerations for operation at cryogenic temperatures are addressed. A flip-chip batch transfer process for tethered MEMS fabricated by Cronos MUMPs process is developed. The electromechanical and RF tests are carried out. The switch exhibits an insertion loss of <0.8 dB up to 40 GHz. Switch designs that improve the isolation by compensating for capacitance in down-state by adding an extend integrated inductance have been proposed. The simulations of these novel designs have shown that an isolation of better than −22 dB for a specified frequency range can be achieved using this approach.