A Novel Approach to the Design and Implementation of Dual-Band Compact Planar 90<tex>$^circ$</tex>Branch-Line Coupler

Abstract

This paper presents the design of a novel branch-line coupler that can operate at two arbitrary frequencies. The proposed circuit also features compact size and planar structure. Explicit design formulas of the proposed dual-band coupler are analytically derived. Moreover, practical issues such as the realization of branch-line impedance and optimum choice of circuit topologies are addressed. For verification purposes, both simulated and measured results of a microstrip branch-line coupler operating at 900/2000 MHz are included.