Reduced-size branch-line and rat-race hybrids for uniplanar MMIC´s

A method of miniaturizing branch-line 90° hybrids and 180° rat-race hybrids is proposed. The method utilizes combinations of short high-impedance transmission lines and shunt lumped capacitors. The hybrids were fabricated on GaAs substrates and the validity and effectiveness of the method were confirmed through experiments at 25 GHz and 11 GHz. The fabricated hybrids demonstrate excellent design accuracy at high frequencies, with a circuit size that is more than 80% smaller than that of conventional hybrids. These hybrids are particularly suitable for uniplanar MMICs where necessary shunt connections are easily made