Liquid metal feasibility and characterisation in reconfigurable antenna applications.

Abstract

This thesis presents the feasibility of liquid metal in reconfigurable antenna applications. Unlike conventional reconfigurable antennas, liquid metal possesses the ability to reconfigure an antenna aperture in new ways largely undiscovered. In this work, the design, analysis and measurement of two liquid metal reconfigurable antennas are carried out bringing together research on materials, microfluidics and electromagnetics. In addition, a like for like comparison of applying liquid metal and PIN diode in pattern reconfigurable antennas is presented. On the RF characterisation, test fixtures are designed, analysed and measured to evaluate liquid metal and copper up to 67 GHz, and PIN diode up to 6 GHz. While various liquid metal antennas exist, the current state of the art has mainly implemented liquid metal in point-like contacts or limited confined areas. On how liquid metal can be used to connect/disconnect large areas of metalisation and achieve radiation performance not possible by using conventional switches is demonstrated in a frequency bandwidth reconfigurable antenna. The antenna results in a 2 dB gain and 24% efficiency enhancement. The second antenna presents a frequency tunable patch antenna formed from liquid metal. The antenna reconfigures its resonance in a continuous manner. A measured total usable spectrum of 73% is achieved. In the like for like pattern reconfigurable antennas comparison, the liquid metal shows no effect on resonance whereas PIN diodes cause 27% resonance shift. The liquid metal antenna shows up to 1.4 dB gain and 13% efficiency higher than that of the PIN diode antenna. In the RF characterisation, the diode shows up to 6.5 dB higher insertion loss than liquid metal. Liquid metal measurements up to 67 GHz show identical behaviour as of copper. Results conclude that liquid metal has a high feasibility in reconfigurable antenna applications and its RF performance is as of a typical conductor.