A Novel Wideband 3-dB Branch Line Coupler Using Capacitively-Couple Coupled Line

Abstract

This paper introduces a novel 3-dB two-section wideband branch line coupler (BLC). For a wideband characteristic, a capacitively-couple coupled line (CCCL) based BLC design is explored. Proposed BLC is compact in size along with that it maintained a flat coupling and very less amplitude imbalance between through and coupled ports. Without defected ground structures and multilayer process, proposed BLC has better fractional bandwidth (FBW) and lesser circuit size as compared to conventional two section BLC. Designed CCCL based BLC exhibited 43.2% FBW at the center frequency of 3.7 GHz. The bandwidth is constrained by 1-dB power imbalance, ±5 phase imbalance, -12dB worst return loss, and -12dB isolation.