Design of 2 × 4 Filtering Butler Matrix Based on All-resonator Structure

In this paper, a design of 2 × 4 filtering Butler matrix based on all-resonator structure is proposed. Firstly, the structure of multi-beam antenna system is introduced, it is pointed out that the coupler is the most important part of the Butler matrix. Then, a method to design a 180° coupler with filtering characteristics by using resonator is proposed, and then the coupler is applied in the design of Butler matrix. The design method of 2 × 4 filtering Butler matrix is given, and the simulation results show that it has great filtering characteristics.