Multimodal-based shape optimization of a rectangular horn mounted in an enclosure for optimum impedance matching

This study presents a multimodal-based method to optimize the boundary shape of a rectangular horn for optimum impedance matching, assuming that the horn is mounted in an enclosure to adapt to practical applications. An infinite rectangular waveguide with a perfectly matched layer is introduced to solve the multimodal radiation impedances of the horn. The throat impedance of the horn is then calculated using the mode matching method. The optimum impedance matching properties over a wide frequency range are obtained by performing gradient-based shape optimization. The results show that the choice of target frequency band can significantly affect the optimization results. The numerical model is verified by the finite element method. The impedance matching performance of an optimal horn design is also experimentally validated.