Dual-Function Circuit with Crossover/Branch-Line Coupler Characteristics

A dual-function circuit with the properties of a crossover at one frequency and the properties of a branch-line coupler at another frequency is introduced in this paper. The circuit can be realized by using planar transmission lines, the electrical lengths and characteristic impedances of which can be explicitly determined by even-odd mode analysis. It is found that the concept of a dual-band circuit can be applied to facilitate the design. A prototype which acted as a crossover at 2.45 GHz and as a branch-line coupler at 5.8 GHz has been designed and implemented. Both of the simulated and measured results validate the dual-function characteristic of the proposed circuit.