Design of a Three-Branch Line Quadrature Hybrid Coupler with Reduced Size

Abstract

This paper presents a design of a three-branch line quadrature hybrid coupler with reduced size implemented in the microstrip line. The designed coupler is to be used in the feeding of a crossed-dipole circularly polarized antenna for receiving GNSS signals at 1.16-1.61 ㎓. The performances of the two- and three-branch line couplers are investigated first. Characteristic impedances of the three branch lines are adjusted for a better balance in coupling coefficients. To reduce the size of the three-branch line coupler, the main lines are meandered inward and outward using the optimized coupler. Meandering reduces the size of the quadrature hybrid coupler by 35.2% in one direction. The outward-meandered coupler shows slightly larger bandwidth than the inward-meandered design. The outward-meandered coupler shows magnitude and phase imbalances of 0.36 ㏈/0.7° at 1.16 ㎓, and 0.43 ㏈/0.8° at 1.61 ㎓.