Miniaturized dual-band coupler using three-branch-line structure and dual transmission lines

Abstract

This letter presents a compact dual-band branch-line coupler. Explicit design formulas of the three-branch-line coupler (3-BLC) are derived and useful design curves are given. The equivalent dual transmission lines structure is used to decrease the dimension, and also the partial branch lines are folded to further miniaturize the design. The proposed dual-band (2.45 and 5.8 GHz) coupler has a compact size with 57.6% size reduction compared with the conventional circuit. The measured and simulated results are in good agreement with each other. Keywords: dual-band coupler, compact size, three-branch-line structure, dual transmission lines Classification: Microwave and millimeter-wave devices, circuits, and modules References[1] C. Collado, et al.: "Dual-band planar quadrature hybrid with enhanced bandwidth response," IEEE Trans.