Microwave filters play key roles in controlling the frequency response at specific locations of any communications, radar, or test system. Microwave resonators provide the frequency selective building blocks necessary for filter design. Reconfigurable/ tunable microwave resonators have facilitated the design of tunable filters. Recently, MEMS based tuning mechanisms developed widely tunable resonators maintaining high Q; however, limit in the number of reconfiguration states. This thesis proposes a fluidic-reconfigurable Xband SIW resonator capable of continuous tunability across the reconfiguration range. A dielectric post of fluidic dispersions with variable material properties embedded in a two inductive post static SIW resonator defines the tuning mechanism. The development of an analytical closed-form expression for the resonant frequency and Q across reconfiguration, a circuit model, and full-wave simulation predicts the tunable performance with estimated material properties of the fluidic dispersion. Measured data on an initial tunable SIW resonator design showed good reconfiguration performance but more losses than expected which could potentially be explained from the discovery of a major design error not associated with the resonator itself. A second tunable SIW resonator designed and fabricated proves the material properties of the fluidic dispersions contain more losses than estimated and hinder the resonators performance. By comparing simulated and measured data new estimates for the material properties of the fluidic dispersion are proposed which agree with trends in recent literature. Low-loss fluidic dispersions will enable a significant performance increase in the current tunable SIW resonator. Two low-cost material measurement systems are designed to expedite research efforts in finding low-loss microwave fluidics. Both systems accurately compute dielectric constant but not loss tangents. The initial systems provide necessary first steps in the design of future highly accurate material measurement systems.

<div>The allocated frequency bands for the incoming fifth generation (5G) wireless communication technologies spread broadly from sub 6 GHz to K and potentially W bands. The evolution of the future generations toward higher frequency bands will continue and presents significant challenges in terms of excessive system complexity, production and maintenance costs. Reconfigurable radio architecture with frequency-tunable components is one of the most feasible and cost-effective solutions to meet such challenges. Among these technologies, evanescent-mode (EVA) cavity tunable resonator have demonstrated many of the needed features such as wide tunability, low loss and high linearity. Such a technology typically employs a movable membrane that controls the resonant frequency of a post-loaded cavity. </div><div><br></div><div>The first part of this work focuses on advancing such technology into the mm-wave frequency bands and beyond. Manufacturing tolerance and tuner performance are the two main limiting factors addressed here. This work develops a cost-effective micro-fabrication and package assembly flow which addresses the manufacturing related limitations. On the other hand, introducing micro-corrugated diaphragms and gold-vanadium co-sputtered thin film deposition technology, significantly reduces (4 times) the tuning voltage and enhances tuning stability (7 times). We demonstrate a tunable two-pole band-pass filter (BPF) prototype as the first EVA cavity tunable filter operating in the K-Ka band. </div><div><br></div><div>The second part of this work extensively discusses an optimal RF design flow based on the developed manufacturing technology. It considers all technology constrains and allows the actualization of a high Q transfer function with minimum bandwidth variation within an octave tuning range. Moreover, a new fully passive input/output feeding mechanism that facilitates impedance matching over the entire tuning range is presented. The devised RF methodology is validated through the design and testing of a two-resonator BPF. Measurements demonstrate a tuning range between 20-40 GHz, relative bandwidth of 1.9%-4.7%, and impedance matching over the entire tuning range which is upto 2 times better than previously reported state-of-the-art MEMS tunable filters of this type.</div><div><br></div><div>The third part of this work further advances the technology by proposing the first MEMS-based low-power bi-directional EVA tuning approach that employs both the main bias circuitry as well as a new corrective biasing technique that counteracts viscoelastic memory effects. The two key enabling technologies are extensively discussed: a) a new metal-oxide-metal (MOM) sealed cavity that maintains high quality without requiring complicated metal bonding; and b) a new electrostatic bi-directional MEMS tuner that implements the needed frequency tuning without lowering the resonator quality factor. </div><div><br></div><div>Furthermore, we explore important design and fabrication trade-offs regarding sensitivity to non-ideal effects (residual stress, fabrication imperfections). Measurement of the new prototype bi-directional design, prove that this technology readily corrects residual post-bias displacement of 0.1 um that shifts the frequency by over 1 GHz with less than 2.5 V. It takes over 100 seconds to recover this error in the uni-directional case. This correction does not adversely affect the filter performance.</div>