A Simple Design Procedure for the Asynchronous Box-Section Filter

Design of a box-section filter with asymmetric frequency response would introduce non-zero diagonal elements in the coupling matrix. These non-zero diagonal elements would cause a shift of resonant frequency for each resonator and the coupling coefficients would not easily be determined accurately without heavy and complicated iteration process. In this paper, a new and simple design procedure for the asynchronous box- section filter is presented. Through the proposed design procedure, the dimensions of resonators and the coupling coefficients can be extracted systematically, and the iteration time for fine tuning can be reduced drastically. To demonstrate the benefit of proposed design procedure, a fourth-order multilayer box-section filter with one transmission zero is carefully designed, fabricated, and measured.