A High Q Substrate Integrated Waveguide Resonator for Microwave Sensing of Low Loss Materials

Abstract

A substrate integrated waveguide (SIW) cavity based high Q-resonator is presented in this paper. The high Q-factor of the designed SIW cavity is achieved by optimizing the microstrip feeding topology, which actually controls the coupling from external circuitry to the designed resonator structure. The optimization of the microstrip feeding enhances the quality factor of the resultant resonator by one order of magnitude in comparison to the conventional microstrip fed SIW resonators. The proposed feeding design also reduces the loading effect of external circuitry on the designed resonator. The microstrip coupling makes the proposed SIW resonator fully planar structure, which can be easily integrated with other microwave circuit components. The design of proposed resonator is carried out using the 3-D EM simulator (CST-MWS) and accordingly various parameters are optimized to obtain the desired performance in the specified frequency region. For validation purpose, the proposed resonator along with a conventionally fed microstrip resonator is fabricated on the Roger RT 5880, and measurement is performed using network analyzer. The measurement results are found to be in closed agreement with the simulated data. The proposed high-Q SIW resonator can be employed for design of highly selective compact filters, and can also be used as RF sensor for the accurate characterization of low loss dielectric materials.