High-Q RF-MEMS 46-GHz Tunable Evanescent-Mode Cavity Filter

This paper presents a miniature high-tunable evanescent-mode cavity filter using planar capacitive RF micro-electromechanical system (MEMS) switch networks and with a frequency coverage of 4.07-5.58 GHz. The two-pole filter, with an internal volume of 1.5 cm, results in an insertion loss of 4.91-3.18-and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, and an ultimate rejection of 80 dB. RF-MEMS switches with digital/analog tuning capabilities were used in the tunable networks so as to align the two poles together and result in a near-ideal frequency response. The measured of the filter is 300-500 over the tuning range, which is the best reported using RF-MEMS technology. The filter can withstand an acceleration of 55-110 g without affecting its frequency response. The topology can be extended to a multiple-pole design with the use of several RF-MEMS tuning networks inside the evanescent-mode cavity. To our knowledge, these results represent the state-of-the-art in RF-MEMS tunable filters.