A Mode Reduction Metal Resonant Cavity Frequency Tuning Method and Application

A frequency tuning method for metal resonant cavities is proposed that combines perturbation tuning and mode reduction. By keeping the dimensions of the resonant cavity unchanged, a tuning structure is introduced inside the cavity to reduce the resonant frequency. The complexity of the tuning is reduced and the optimisation efficiency is improved by decomposing the higher-order modes of the resonant cavity into the main mode. To verify this method, a resonant cavity with a fixed length and width of 24 mm operating in the TE440 mode is designed. The problem of large scale higher order modes is transformed into the problem of solving the resonant frequency of the main mode in a smaller cavity. By optimising and adjusting the tuning structure, the resonant frequency of the resonant cavity is reduced from 35.36 GHz to the desired 30 GHz. Subsequently, this dimension is scaled up to a 24mm cavity to obtain the required higher order modes, and finally, a 4×4 element metal resonant cavity slot antenna array is designed using this resonant cavity to demonstrate the practicality of the proposed method.