A Coupled SIW Cavity Fast Frequency-Scanning Antenna Based on Characteristic Mode Analysis

Based on the characteristic mode analysis (CMA), our earlier study (Fu et al., 2021) introduced a theoretical method for designing frequency-scanning antennas using coupled patch antenna arrays: adjacent mode pairs can be superimposed under specific conditions to achieve a high-gain, low-sidelobe beam whose direction scans with frequency. As an extended study of the above method, to improve the scanning rate and range, the design of a tightly coupled substrate integrated waveguide (SIW)-based slot array is proposed in this letter. With the aid of CMA, this letter provides an effective way of controlling the spectral characteristics of certain modes by adjusting the window size between cavities, which in turn enhances the scanning rate and scanning range. Simulation and experimental results validate the proposed approach. Over the sub-6 GHz band from 5.19 GHz to 5.39 GHz, the proposed antenna has achieved a scanning range from 15° to 75°, and a scanning rate of 15.9%. It maintains an average gain of 9.5 dBi with a radiation efficiency of 79%.