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This thesis presents high-Q tunable filter RF-MEMS and Schottky diode fillters for the 1-6 GHz frequency range. A new admittance matrix filter design method has been developed, and several hybrid-coupling filters were analyzed and designed using this method. The source-load impedance loading is also introduced, and this enables a filter design with an arbitrary loss. These design principles were applied to several filter examples and proved to be very useful, especially for ones with intricate geometries. With the unique independent electric and magnetic coupling filter topology, low-loss tunable (Schottky varactor diode) filters with three different fractional-bandwidth variations (constant, decreasing, and
increasing fractional-bandwidth) are obtained. The measured filters have frequency tuning ranges of 800-1400 MHz, and their insertion-loss, and Qu are 1.0-3.0 dB and 60-150, respectively. These planar tunable filters represent the state-of-the-art insertion loss performance in this frequency range. For RF-MEMS tunable filters, the lossy coupling between the resonant electric field and bias-lines is first addressed, and a high-Q multi-bit orthogonal
RF-MEMS capacitance network is introduced. As a result, a state-of the-art 4-6 GHz multi-bit RF-MEMS tunable filter is realized with a measured insertion loss and Qu of 1.5-2.8
and 85-170, respectively. To author's knowledge, this is the highest-Q tunable planar filter to-date at this frequency range. A 5.10-5.80 GHz CPW RF-MEMS switchable filter with mirrored transmission zero responses is also introduced, and an isolation enhancement of > 10 dB between two frequency bands is realized. Finally, a very high-Q evanescent-mode tunable filter with a novel high-Q RF-MEMS cantilever-switch capacitance network is presented. The loss mechanisms of the RF-MEMS capacitance network in the high-Q evanescent-mode resonator are investigated and a bias-line metal-bridge cover and an RC network in the bias-path are introduced. The measured filter frequencies, done on fixed capacitance value prototypes, their insertion loss, and Qu values are 4.19-6.59 GHz, 2.46-1.28 dB, and 538-845, respectively. |
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