Novel Multifunctional Dual-Band Coupled-Line Coupler With Reuse of Low-Frequency Trans-Directional and High-Frequency Contra-Directional Functions

摘要

In this brief, for the first time, a novel multifunctional dual-band coupled-line (CL) coupler with reuse of low-frequency trans-directional (TRD) and high-frequency contra-directional (CTD) functions is presented. It is composed of three cascaded CLs with an overall electrical length of 90 degrees and four shunt capacitors, which achieves a compact circuit configuration in microstrip implementation. Since capacitors are shunted between the CLs, the coupler is easy to realize tight coupling with miniaturized size and has an inherent feature of dc blocking. Moreover, different power ratios can be realized over two designated frequencies. Frequency conversion leads to the location change of the isolation port, which eventually leads to the reuse of the circuit and port function expansion of the coupler. Good agreements between the simulated and measured results verify the design theory.