Reconfigurable Liquid Metal Based SIW Phase Shifter

Abstract—This paper presents the first substrate integrated waveguide (SIW) phase shifter that can be reconfigured using liquid metal. This digital phase shifter exhibits low insertion loss and is reciprocal and bidirectional. It incorporates a series of holes which can be filled or emptied of liquid metal, enabling us to add or remove via connections dynamically, on-the-fly. By using a collection of such holes, it is possible to create a wall along the E-plane or H-plane of the waveguide. When the wall is in place, it blocks the passage of energy. When the wall is absent, energy is able to flow. In this way, it is possible to guide the electromagnetic (EM) waves through 1 of 3 paths, having different electrical lengths. The result is a digital switched-line phase shifter that achieves coarse steps of phase change, from 0 up to 180°, in steps of 60°. By filling or emptying individual holes it is possible to introduce reactive loading into each path. In this way it is possible to achieve fine phase control in steps of 10°. By employing both forms of reconfiguration in unison the proposed phase shifter is able to deliver a phase shift of up to 180°, in steps of 10°. The proposed phase shifter operates at 10 GHz and exhibits an insertion loss of less than 2.3 dB over its entire operating band. Furthermore, the underlying concept of the proposed phase shifter can be readily scaled for operation in the millimeter wave band. Existing phase shifters operating in that band exhibit significant insertion losses. Millimeter wave phase shifters are expected to find application in 5G mobile access points