In situ monitoring of dynamic bounce phenomena in RF MEMS switches

This paper presents the first ultra-low-power complementary metal-oxide-semiconductor (CMOS)-based measurement technique for monitoring the cold-switched dynamic behavior of ohmic radiofrequency microelectromechanical systems (RF MEMS) switches in real time. The circuit is capable of providing precise information about contact timing and ohmic contact events. Sampling of dynamic events at frequencies of 1 and 5 MHz shows contact timing accuracy of 99% when compared with real-time true-height information obtained from laser Doppler vibration data. The technique is validated for an ohmic RF MEMS switch with multiple bounces. The actuation voltage has also been designed to enhance bouncing behavior to more clearly study the performance and limits of the presented technique. More than 13 bounces are successfully captured by the electronic measurement technique. The weakest bounces exhibit vertical displacements of less than 20 nm as recorded by a laser Doppler vibrometer. This demonstrates the ability to capture precise timing information even for weak contacting events. A detailed discussion of how parasitics influence this technique is also presented for the first time.