Analysis Method for a Multi-Section Rat-Race Hybrid Coupler Using Microstrip Lines

Abstract

An analysis method for a multi-section rat-race hybrid coupler with a large bandwidth is presented. The proposed coupler has only a few additional microstrip lines compared to a single-section coupler. A complete analysis method is derived and validated through even- and odd-mode analysis, considering the asymmetric structure of the proposed coupler. To demonstrate the effectiveness of the design, two two-section rat-race couplers with an operating frequency of 2 GHz and splitting ratios of 1:1 and 1:2 were simulated and fabricated. Measurements of the fabricated couplers yielded results in good agreement with the simulation results, demonstrating wide bandwidth characteristics.