Abstract
A planar, simplified, dual-band rat-race hybrid with arbitrary power division ratio is presented. It is accomplished by inserting only single additional shunt stub in the conventional structure and modifying the lengths and characteristic impedances of the arms. Using rigorous even- and odd-mode analysis, the explicit closed-form equations for this hybrid are derived. Based on the standard microstrip technology, the relationship between the realizable power-split ratios and the frequency ratio is investigated. As a generalized design, it is found that traditional rat-race hybrid and some previous compact structures are special cases of the proposed hybrid. With this method, a prototype operating at 1/3.5 GHz with 7.96 dB power division ratio is designed, fabricated and measured. The validity of this design has been proved by the consistency of the simulation and measurement results.
Acknowledgements
The research was supported by the National Natural Science Foundation of China (No. U1234205 and 20120009110005), National Science and Technology Major Projects (2011ZX03001-007-01) and the Fundamental Research Funds for the Central Universities (Nos. 2011JBM207 and 2011JBZ001).