Planar, Multifunctional 3D Printed Antennas Using Liquid Metal Parasitics

This paper describes a liquid metal-based multifunctional antenna capable of wideband frequency tuning, dual band operation, and polarization reconfiguration. The radiating elements consist of parasitically-excited plugs of room-temperature liquid metal in 3D printed channels. Syringe pumps flow the gallium-alloy plugs in proximity to a capacitive feeding structure. This non-contact feeding scheme separates the metal flow path from the SMA connector and lends mechanical robustness at the feed while allowing impedance matching over a wide range of frequencies. Sliding the plug along a right-angle bend enables linear polarization reconfiguration, while simultaneously placing plugs in both orthogonal channels can generate circular or 45 degrees linear polarization. Dual band operation is also supported by infusing plugs of two dissimilar lengths into the two channels. Simulation and measurement results demonstrate that this antenna can tune its impedance over a decade (10:1 frequency range) maintaining a 2:1 VSWR and achieve a polarization diversity >12 dB. The pumped plugs can circulate at a peak velocity of 50 mm/s, currently limited only by our pumping equipment. Repeatability analysis is also performed by cycling the plug actuation more than 1100 times. More complex designs can exploit this design concept to develop new types of highly versatile, multi-functional antennas.