Compact Dual-Band Branch-Line Coupler with Enhanced Bandwidth for WLAN Applications

摘要

Dual-band operation with enhanced bandwidth and small size are important performance figures of hybrid couplers for applications in modern communication systems. Unfortunately, maintaining broad frequency ranges of operation stays in conflict with circuit miniaturization. In this work, a compact dual-band branch-line coupler (BLC) with improved bandwidth has been proposed. Electrical performance of the structure has been improved by introducing an asymmetry into the cross-coupled branches of the reference dual-band circuit. The coupler has been optimized at a low computational cost using a surrogate-assisted method. It features 180 MHz and 450 MHz bandwidths at the center frequencies of 2.45 GHz and 5.4 GHz, respectively. The footprint of the optimized circuit is only 296 mm². The coupler has been benchmarked against competitive dual-band BLCs from the literature.