An efficient design method of microstrip filtering antenna suitable for circuit synthesis theory of microwave bandpass filters

This paper proposes an efficient design method of filtering antennas, enabling to apply a well-established filter design theory to the antenna design. In the design of filtering antenna, an external Q factor at input port, coupling coefficients, and a radiation Q factor of antenna need to be evaluated. However, conventional design methods have a time-consuming procedure, since a time domain response from the overall structure is required for the evaluation of coupling coefficient between resonator and antenna. For an efficient design, we propose a parameter extraction technique using only amplitude property of input reflection responses for the evaluation of both the coupling coefficient and the radiation Q factor. As an example, a third-order filtering antenna is synthesized, designed, and tested, which numerically and experimentally validates the effectiveness of the proposed design method.