A Wide-Band Quadrature Hybrid Coupler (Correspondence)

Wide-band quadrature hybrid proximity couplers consist of a conductor fabricated by thin-film techniques in microstrip the conductor side and a slot in the ground plane side. A 4 to 1 bandwidth was achieved using an alumina substrate of 99.6-percent purity with a surface finish of 10 /spl mu/in. A single-section quadrature hybrid has been fabricated and operates over a 2.5- to 10-GHz frequency range with a maximum VSWR of 1.43:1, a 20-dB typical isolation, and a phase difference between outputs of 90/spl deg/ /spl plus mn/ 3/spl deg/.