Design of broadband semi-lumped and lumped element quadrature hybrids

Abstract

Band-broadening techniques for semi-lumped and lumped element quadrature 3 dB hybrids are described. A semi-lumped hybrid is spiral-inductor-free, and the occupied area is about 1/150 compared with a distributed-element one at 1 GHz band. In lumped-element version, two kinds of matching networks are dealt with; one consists of an admittance inverter and a parallel tuned circuit, and the other makes good use of a series one. The former is marked by lower inductance values and the latter by less devise count and wider bandwidth. The frac- tional bandwidths of the designed hybrids are 20-27% for return loss better than 20 dB and amplitude balance tolerance 0.18 dB. Index Terms — directional couplers, lumped element micro- wave circuits, microwave integrated circuits, passive circuits.