A novel dual-band crossover design with enhanced frequency band ratio and operating bandwidth

This paper presents the novel design of a dual-band crossover based upon the combined structure of tri-section branch-line coupler and dual-band transformer. The proposed circuit features planar structure, wide operating bandwidth as well as inter-band suppression capability. Explicit closed-form design equations are derived by using even- and odd-mode analysis. For verification, both simulated and measured results of a dual-band crossover (1, 2 GHz) with an operating bandwidth of around 150 MHz and port isolation of over 20 dB are shown.