Multi-Way and Poly-Phase Aligned Feed-Forward Differential Phase Shifters

Abstract

Traditional two-way passive differential phase shifters (DPSs) are comprised of a reference line and a delay line. To realize a passive multi-way poly-phase DPS, a single reference line is not possible and a cascaded network becomes necessary. This results in both a cumbersome and complex structure, with large phase error that propagates through the network. A novel phase shifter is presented here that allows multi-way and poly-phase differential phase shift using just one common reference line. This phase shifter is constructed using a newly proposed phase-shift component in all element designs, where each element maintains a constant phase shift with adjacent elements. This characteristic for DPSs offers a simple solution to multi-way poly-phase systems, such as those found in phased arrays. To validate the proposed concept, phase shifters are designed as a group of five different elements operating at 2 GHz, with each maintaining a constant phase shift (45 $^{\circ}$ , 90 $^{\circ}$ , 135 $^{\circ}$ , 180 $^{\circ}$ ) compared to a reference element. Measured results agree well with the theoretical analysis. Over a 40% bandwidth the achieved phase shifts are ${\hbox{45}}^{\circ} {\pm} {\hbox{0.9}}^{\circ},$ ${\hbox{90}}^{\circ} {\pm} {\hbox{1.5}}^{\circ},$ ${\hbox{135}}^{\circ} {\pm} {\hbox{4}}^{\circ}$ , and ${\hbox{180}}^{\circ} {\pm} {\hbox{4.2}}^{\circ}$ , while amplitude imbalances are all less than 0.25 dB.