An alternative implementation for fabricating a Schiffman phase shifter

This article presents an alternative implementation for fabricating a Schiffman phase shifter. The method consists of initially deciding the gap width between the coupled microstrip lines and using the derived equation to determine the width of the coupled microstrip lines. The proposed approach does not have to remove the ground plane underneath the coupled microstrip lines and install an additional isolated rectangular conductor under them. One Schiffman phase shifter is designed and fabricated on a double-sided FR4 printed circuit board as an example to verify the performance of the proposed approach, and the design is simulated using Ansoft HFSS and validated by the measurements. The simulated and measured return losses are found to be better than -15 dB over the frequency band from 1.0 to 4.0 GHz and the insertion loss is within -2 dB. The bandwidth in 90 degrees phase difference from 1.6 to 3.4 GHz is about 72%. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:912, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27266