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Abstract
A generalized compact rat-race 180° hybrid with arbitrary power division ratio for matching complex impedance loads is presented in this paper. The proposed structure consists of four-section transmission lines, which is similar to the shape of the traditional hybrid. Compared with the conventional hybrid coupler, this design can be terminated with arbitrary complex impedances and realize high power-split ratio. Because of the symmetry of the proposed structure, it can be calculated by even–odd mode analysis and matrix. The explicit closed-form equations are derived analytically. The bandwidth variations are mainly discussed and simulated. For verifying the validity of this design, a microstrip prototype for 13.98 dB power-split ratio is simulated, fabricated, and measured. The measured performance shows a good agreement with the simulated results.
Acknowledgments
The research was in part supported by the National Science and Technology Major Projects (No. 2010ZX03007-003-04), the National Natural Science Foundation of China (Nos. 61001060, 61201025), and the Fundamental Research Funds for the Central Universities (No. 2012RC0301).