CMOS-based monitoring of contact events up to 4 MHz in ohmic RF MEMS switches

This paper presents an ultra-low power, fully electronic methodology for real-time monitoring of the contact events of ohmic RF MEMS switches. The measurement is based on a resistive readout circuit composed of 67 transistors with a 105 µm × 105 µm footprint. This is coupled with a novel implementation of a single-crystal silicon switch capable of operating from DC-40 GHz. The CMOS readout electronics tap the RF circuitry through two 1.6 kΩ resistors that add negligible insertion loss to the switch. Experimental and theoretical results demonstrate that timing information for the switch contact behavior is accurately measured for all consecutive bounce events that occur during the time it takes for the switch to come to a fully closed state (25–30 µs). A simple one-dimensional contact model agrees to within 10–20% with the measured landing times. In addition, a finite contact duration of 2–3 µs for each landing is accurately captured experimentally. This demonstrates the potential of this technique to real-time on-chip dynamic monitoring of contacts for packaged RF MEMS switches through their entire lifetime and after their integration in the final system.