Determining a Perturbation Factor to Design Tunable Resonant Cavities in SIW Technology

Abstract This paper presents an effective and novel design procedure employing a novelty named as Perturbation Factor to predict the resonance frequency of resonant cavities in SIW technology perturbed by a shape perturbation. The design procedure can be applied in tunable cavities and bandpass filters with shunt reactance of symmetrical inductive window, and regarding the application technologies, rectangular waveguide resonators and resonant cavities in SIW can be employed due to the equivalence of operation between both technologies. Its straightforward application allows a frequency variation of up to 20% using only one metal post which allows the reduction of the fabrication cost and the preservation of the frequency response across the considered bandwidth. To validate the design procedure, two resonant cavities were fabricated, a rectangular resonant cavity designed to operate at 5.0 GHz and 6.0 GHz and a square resonant cavity designed to operate at 6.0 GHz and 7.2 GHz, and frequency variations of 17.74% and 21.81% were obtained for the rectangular and square cavities, respectively. Still regarding the reached results, was verified a mean error of 1.75% for the predicted resonance frequency, which validates the design procedure. The experimental results are in good agreement with the full-wave computational results and electromagnetic theory.