Recent advances in metamaterials research has enabled the development of highly sensitive near-field microwave sensors with unprecedented sensitivity. In this work, we take advantage of the increase in the sensitivity to produce a compact, lightweight, affordable, and accurate measurement system for the applications of microwave imaging and material characterization. This sensitivity enhancement due to the inclusion of metamaterials opens the door for the use of inexpensive microwave components and circuits such as direct detectors while leveraging the high sensitivity of the metamaterial probe to deliver an overall accurate measurement system comparable to that of a traditional probe used in conjunction with a vector network analyzer. The sensor developed is composed of a metamaterial sensor with an RF direct detection circuit. In this work, two prototype measurement systems have been designed and tested. Measurement of small cracks in conductors and material characterization using the proposed system were performed. The results from the newly developed sensors were compared with the results from vector network analyzer measurements. Good agreement was obtained. The feasibility of a compact, lightweight, affordable, and accurate system has been demonstrated by using the developed prototypes.

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.

Recent advances in metamaterials research has enabled the development of highly sensitive near-field microwave sensors with unprecedented sensitivity. In this work, we take advantage of the increase in the sensitivity to produce a compact, lightweight, affordable, and accurate measurement system for the applications of microwave imaging and material characterization. This sensitivity enhancement due to the inclusion of metamaterials opens the door for the use of inexpensive microwave components and circuits such as direct detectors while leveraging the high sensitivity of the metamaterial probe to deliver an overall accurate measurement system comparable to that of a traditional probe used in conjunction with a vector network analyzer. The sensor developed is composed of a metamaterial sensor with an RF direct detection circuit. In this work, two prototype measurement systems have been designed and tested. Measurement of small cracks in conductors and material characterization using the proposed system were performed. The results from the newly developed sensors were compared with the results from vector network analyzer measurements. Good agreement was obtained. The feasibility of a compact, lightweight, affordable, and accurate system has been demonstrated by using the developed prototypes.