Wide-band lumped-element quadrature 3-dB couplers in microstrip

A design procedure for wide-band quadrature 3-dB couplers at microwave frequencies is presented in this paper, wherein lumped elements are incorporated into a microstrip circuit. Design examples for an octave-band coupler and a one-and-one-half octave-band coupler are presented. The topologies presented offer a convenient and cost-effective solution to tight coupling problems, currently solved using distributed circuits.