Design of a 180-degree hybrid with Chebyshev filtering response using coupled resonators

Abstract

A novel 180 ° hybrid with third-order Chebyshev filtering response is proposed in this paper. The coupling coefficients and the external quality factors can be synthesized from the theory of coupled resonator filter. The proposed idea is verified with experimental results, with good agreement between simulation and measurement. Comparing to the conventional rat-race coupler, 80% size reduction and filtering function with high frequency selectivity has been exhibited in the proposed structure.