Design of microstrip ultrabroadband multisection quadrature hybrid

This paper proposes a three- and a five-section microstrip 3-dB quadrature hybrid. Two types of enhanced coupling structures, both with a rectangular ground-plane aperture and two inserted signal strips in the aperture, are used in the quadrature hybrid not only to achieve tight coupling but also to minimize the junction effect between coupling sections. The designed circuits have a fully planar structure. They were fabricated on a single-layer substrate by the standard printed circuit board (PCB) manufacturing process.