10-GHz Low-Loss Liquid Metal SIW Phase Shifter for Phased Array Antennas

This article presents a proof of concept demonstrator for a pair of novel phase shifters based on substrate integrated waveguide (SIW) technology. Gallium-based liquid metal (LM) is used to reconfigure each phase shifter. This article presents LM phase shifters that, for the first time, have a phase shifting range of 360 degrees. The phase shifters have a small electrical size, and they are intended for use within phased array antenna applications. This article also presents a design procedure for the phase shifters. The procedure has been used to design two phase shifters operating at 10 GHz. The design process can be readily scaled for operation at other frequencies. The proposed phase shifters are reciprocal and bidirectional, and they have very low insertion loss (IL). A series of reconfigurable LM vias are used to achieve the phase shift. Each of LM via is activated once a drill hole is filled with LM and it is deactivated once LM is removed. Using this method, it is possible to achieve a phase shift step ranging from 1 degrees to 100 degrees using a single LM via. Moreover, the overall phase shift can be extended to 360 degrees by employing several LM vias in series inside the SIW. The proposed phase shifters have an IL lower than 3 dB and provide a total phase shifting range of approximately 360 degrees in eight steps of approximately 45 degrees each. This enables the proposed two phase shifters to have an extraordinary figure of merit (FoM) of 131.3 degrees /dB and 122.4 degrees /dB.