This paper presents the development of tunable filters using ohmic contact microelectromechanical system switches. It is shown that this type of switch is very well suited for the fabrication of low-loss high tuning-range microwave filters. Two sets of tunable Ku-band microstrip filters and resonators have been fabricated, with measured tuning ranges of 20% and 44%, and unloaded quality factors better than 75 in all cases. The 2-bit 5.7% fractional bandwidth, tunable bandpass filters exhibit insertion losses lower than 3.2 dB in all states.

We present a novel concept of microwave (MW) power-limiting devices based on reversible semiconductor-to-metal transition (SMT) of vanadium-dioxide thin films integrated on coplanar waveguides. We designed, simulated, and fabricated devices, which can be reversibly driven from a low-loss (<; 0.7 dB) transmission state into an attenuating state (> 20 dB) as the VO₂ material is changing from semiconductor to the metal state when the incident MW power exceeds a threshold value. These devices are broadband and present a tunable threshold power value. They could be easily integrated as protection circuits from excess power in a large variety of MW components.

This paper presents results on high lifetime RF microelectromechanical (RF-MEMS) dielectricless capacitive switches. Using air gap variation only, these RF MEMS capacitive switches achieve a capacitance ratio of 9, associated with small residual charging. The reliability of the switch has been studied, pull-in and pull-out voltages shifts have been observed, modeled and validated with good agreement between model and measurements for a switch held for one month in the down state. The dependence of charging mechanism to the biasing signal is also presented by applying unipolar and bipolar waveforms with different duty cycles. Charging can be modeled using a simple Curie-Von Schweidler equation. It is shown that the duty cycle of the bias signal is strongly accelerating switch failure, and that using bipolar signals improves the lifetime of these switches by several orders of magnitude. The projected lifetime of current RF-MEMS dielectricless switches held in the down state using bipolar signals is several tens of years.