Application of negative group delay active circuits to the design of broadband and constant phase shifters

The new phase‐shifter configuration described in this report uses a negative group delay (NGD) active circuit. In this topology, a classical transmission line is set in cascade with an NGD circuit whose phase slopes are alike, but opposite, to get a constant and broadband phase shift. The proposed approach was validated through the design and measurement of a phase shifter, which exhibited a constant phase of 90° ± 5° over a 75% relative bandwidth around 1.6 GHz. Moreover, as the group delay of the NGD circuit compensated the transmission line one, the overall circuit group delay was kept to a small value in the operating frequency band. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3078–3080, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23883