Research On Silicon-based MEMS Phase Shifters In RF Receive And Transmit Module Applications

The radio frequency and microwave phase shifter, which can change the phase of the electromagnetic waves, is the kernel components of radar detection, satellite communication, and mobile communication systems. Compared to FET and diode-based phase shifters, the radio frequency micromechanical (RF MEMS) phase shifter has many outstanding performances, such as broadband, low loss, miniaturization. Therefore, the MEMS phase shifter has a brilliant perspective in RF circuit application, especially in receive and transmit module.This thesis mainly presents a one-bit digital switched-line MEMS phase shifterand its component------the contact shunt MEMS switch. As the basis of the researchwork, a brief introduction has been firstly given to the structure and principle of the distributed MEMS phase shifter, the switched-line MEMS phase shifter and the reflection type MEMS phase shifter.Since the operating voltage of the switched-line MEMS phase shifter depends on the pull-in voltage of its contact shunt MEMS switch. Instead of the double clamped and single-actuated model, the double-clamped and double-actuated model is used to precisely predict the pull-in voltage of the contact shunt MEMS switch, which is one of the innovative works of this thesis. The comparison to the measured data demonstrates that the double-actuated model improves the voltage error less than 1%, while the single-actuated model provides the voltage error only less than 10%. Based on the double-actuated model, the pull-in voltage of the contact shunt MEMS switch can be optimized by many structural improvements, such as the reducing the gap between two electrodes, decreasing the initial air gap, thinning the thickness of suspended bridge, lessen the length of the bridge and widening the width of two electrodes.A one-bit digital switched-line MEMS phase shifter has been fabricated, with the phase shifter of 45.27° at 10GHz, which is the another innovative work of this thesis. The phase error of the phase shifter is less than 10%, and the insertion loss isbetter than — 1.7dB in the frequency range of 50M—40GHz.At the last, an analog distributed MEMS phase shifter has been fabricated. The distributed MEMS phase shifter provides the continuously changed phase shifter in the range of 0° ~ 250°, and insertion loss better than -1.7dB.The experiment results suggest a reasonable design, an appropriate materical choice and a feasible process arrangement. The conclusion is constructive to deeper research in the MEMS device fields.