Design of microwave wide-band quadrature hybrid using planar transformer coupling method

A lumped-element quadrature hybrid consisting of two-section inductive coupled (pi)-networks is presented. A synthesizing method involving a new set of design equations are also developed to realize the proposed hybrid with very good balance in both magnitude and phase between the output ports over a 38% fractional bandwidth. The measurements of the two prototypes show quite good agreement with the theoretical predictions. The proposed hybrid is compact and suited to be implemented by conventional microwave-integrated-circuit technology.