In this article, a prototype X band scale model of a quasi‐optical phase shifter is characterized to demonstrate the utility of the architecture proposed. The prototype arrangement utilizes three double layer split slot ring frequency selective surfaces. It is shown experimentally that the transmission phase of an incident linearly polarized signal can be varied from 0 to 2 π radians over the frequency range of 9.5–10.3 GHz in a linear manner. Over this frequency range, the insertion loss of the assembly varies between 2.5 dB, at 10 GHz, to 6 dB at 9.6 GHz, while axial ratio varies between 25 dB to a worst case value of 5 dB. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:972–974, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25931