The RF MEMS technology enables designs of high-performance 3-D integrated microwave systems. It has the potential to revolutionize the design of a wide variety of communication systems, sensors, and radars by improving their loss, volume, weight, agility and signal adaptivity. However, the power handling of conventional RF MEMS switches is restricted by the limited contact area between the contact solid surfaces. Existing solutions for this critical issue primarily focus on improving the contact force and contact materials with limited success thus far. Our goal on the other hand is to investigate alternative approaches that rely on liquid dielectric and metal materials.
Liquid-metal switches are the center of attention for the first part of the dissertation. This technology yields the first liquid-metal shunt capacitive switch with excellent RF performance: 0.06-dB insertion loss and 20-dB isolation at 20 GHz. Subsequently, the toxic metal of this switch is successfully replaced with an environmentally-friendly gallium alloy. The proposed device also exhibits a significantly extended bandwidth of 100 GHz.
Besides liquid metals, water is also considered for liquid switches. Its microwave absorptive properties enable the first MEMS high-frequency absorptive switch. Furthermore, a Ka-band waveguide water absorptive switch integrated with micropumps is demonstrated with power handling greater than 40 W.
The final part of the dissertation discusses thermal management solutions that are critical in compact high-power RF systems. Two schemes that focus on microwave and micro-cooling co-design are proposed.
