Miniaturized High-Q Tunable RF Filters

This dissertation focuses on the investigation and development of novel efficient tuning techniques and the design of miniaturized high-Q tunable RF filters for high-performance reconfigurable systems and applications. First, a detailed survey of the available tuning concepts and state-of-art tunable filters is provided. Then, a novel so-called inset resonator configuration is presented for the applications of fixed and tunable coaxial filters. The design procedure of frequency tunable filters with constant absolute bandwidth (CABW) is described, and various tunable inset filters are implemented, offering many desirable merits, including the wide tuning range and stable high-Q with minimum variation. For wide octave frequency tuning ranges with CABW, a second novel concept is presented using so-called re-entrant caps tuners. Beside simplicity and compactness, this technique also features enhanced spurious performance and wider tuning capabilities than the conventional means. Also, in this dissertation, various miniaturized reconfigurable dual-band/dual-mode bandpass filters and diplexers are presented using compact dual-mode high-Q TM-mode dielectric resonators. Furthermore, a novel microfluidic-based ultra-wide frequency tuning technique for TM010-mode dielectric resonators and filters is introduced in this dissertation. In addition to the very wide tuning window, this mechanism has key advantages of low-cost, simplicity, and intrinsic switch-off. Lastly, the dissertation includes a novel bandwidth reconfiguration concept with multi-octave tuning using a single element for coaxial bandpass filters. This mechanism brings many features including the fast tuning, constant high-Q, intrinsic switch-off, and wide BW-reconfiguration

RF MEMS Based Tunable Bowtie Shaped Substrate Integrated Waveguide Filter

A tunable bandpass filter based on a technique that utilizes substrate integrated waveguide (SIW) and double coupling is presented. The SIW based bandpass filter is implemented using a bowtie shaped resonator structure. The bowtie shaped filter exhibits similar performance as found in rectangular and circular shaped SIW based bandpass filters. This concept reduces the circuit foot print of SIW; along with miniaturization high quality factor is maintained by the structure. The design methodology for single-pole triangular resonator structure is presented. Two different inter-resonator couplings of the resonators are incorporated in the design of the two-pole bowtie shaped SIW bandpass filter, and switching between the two couplings using a packaged RF MEMS switch delivers the tunable filter. A tunning of 1 GHz is achieved for two frequency states of 6.3 and 7.3 GHz. The total size of the circuit is 70mm x 36mm x 0.787 mm (LxWxH)