Plasma-Based Power Limitation for Highly Linear MEMS Switch Protection and Isolation Enhancement

A novel hybrid approach integrating a MEMS switch with a gas discharge tube plasma cell to enhance switch survivability and isolation, especially at high incident power levels, is demonstrated. The theory of operation is discussed including consideration of the underlying plasma phenomena as well as the practical integration details. Measurement of a fabricated prototype is presented. Discussion of measurement challenges and potential solutions is accompanied by detailed explanations of measurement practice. Measurements provide insights into applied RF plasmas not present in the body of literature. Wideband enhancement of isolation by more than 10 dB at 50 W incident power is observed in a quasi-absorptive mode with increasing isolation over power. No penalty to the excellent linearity of MEMS switches is detected with a measured IIP3 of 75.3 dBm. Advantages in linearity as compared to semiconductor-based power limiting solutions are shown and demonstrate state-of-the-art performance. An incremental insertion loss of less than 0.2 dB with a return loss better than 12.5 dB is reported. Measurement of the effects on MEMS switch timing parameters as well as time domain characterization of the plasma breakdown is included.