A microdevice with large deflection for variable-ratio RF MEMS power divider applications

In this paper, we present the design and fabrication of a large deflection MEMS actuator directly integrated as a variable-ratio radio frequency (RF) power divider in a waveguide. The device is based on a tilting microplate suspended by SU-8 springs and driven by a vertical comb drive actuator. The fabricated device is characterized by laser Doppler vibrometer and white light interferometer measurements. The dynamic measurement confirms the resonance frequency of the torsional mode being around 370 Hz, from which the spring stiffness has been extracted and used for static modeling of the device. The fabricated microplate devices achieved deflection angles of 5.9° with a dc actuation voltage of 30 V. First RF transmission measurements show good agreement with results from electromagnetic field simulations. A variable power split ranging from equal division up to a ratio of more than 1:2 is measured at 82.5 GHz whilst keeping the amount of dissipated power below 25%. This is the first reported actuated RF MEMS device integrated in a metal waveguide operating at such high frequency.