Ultra-wideband phase shifter using broadside-coupled microstrip coplanar waveguide

A compact planar phase shifter with ultra-wideband (UWB) performance and 180° differential phase shift is proposed. It utilizes a broadside-coupled microstrip/coplanar waveguide (CPW). Thus, the proposed device can be fabricated using a simple double-side printed circuit board. Four open-ended stubs are added to the microstrip patches and CPW in order to achieve the required 180° phase shift. The designed phase shifter operates across the band from 4.2 GHz to 11 Ghz with less than ±10° differential phase imbalance, and less than 1 dB insertion loss.