Wideband differential phase shifters using slow-wave microstrip line structure

This paper presents a design of broadband phase shifters using a slow-wave microstrip line structure. The slow wave structure is realized by placing periodic circular grounded metal patches below the top layer metal strip. The slow wave structure provides linear phase response over a wide range of frequency which is then utilized to design the broadband phase shifters. A set of graphs are presented to ease the design procedure. The main advantage of the proposed structure is that any phase shift value over the range 0°–360° can be designed. To verify the proposed technique, a prototype 90° differential phase shifter is fabricated for X-band application. The measured reflection loss is more than 22 dB and insertion loss is less than 0.88 dB. Also measured phase deviation is below 8° over the whole band.