A Novel Electronically Tunable SIW Cavity With Wide Discrete Frequency Variation Using Dual-Mode Perturbation

This study presents a complete process for designing electronically tunable SIW cavities with wide frequency variations by perturbing the TE₁₀₁ and TE₁₀₂ resonant modes. Two major and novel contributions are presented. Firstly, an investigation of six different resonant modes is conducted to identify the optimal modes for designing tunable cavities with wide frequency variations. The study demonstrates that the TE₁₀₁, TE₁₀₂, and TE₂₀₁ modes are preferable for achieving wider frequency variations while maintaining an acceptable reduction in the cavity quality factor. Finally, a novel, low-loss, electronically tunable SIW cavity, perturbed by a set of three grounded metal posts controlled by PIN-diode switches, was designed to resonate in the fundamental mode at 3.4 GHz, considering 5G applications, and was subsequently fabricated. The experimental results of the designed tunable cavity demonstrated discrete-step tuning of its resonant frequency over bandwidths of 15.7% and 21.7% for the TE₁₀₁ and TE₁₀₂ modes, respectively. These tunable bandwidths are around 2 times wider than those reported previously for cavities perturbing two different modes. Field-distribution analyses were performed throughout the study using computational simulations. The cavity performance obtained by full-wave simulation was compared with the experimental results, demonstrating an excellent agreement of the cavity input reflection coefficient for the different tuning states of the cavity.