Development of conformal reconfigurable metamaterial-based antennas

Abstract

Antennas are vital components of any wireless communication device. There has been a wide demand for novel flexible and reconfigurable wireless devices as a result of the rising user applications. This thesis presents the design of flexible low-cost antennas using metamaterial loadings with performance characteristics that can be reconfigured by employing microfluidics. In applications such as biomedicine, this work presents an inkjet-printed dipole antenna on flexible Kapton-foam substrate to be used on lossy host structures. The concept of Artificial Magnetic Conductor (AMC) unit cells is investigated for best impedance and gain performance. When integrated with a dipole radiator, the fabricated AMC-backed antenna maintains broadside radiation with gains of up to 4.8 dBi under planar and bending conditions, and on a lossy blood bag. Antenna reconfiguration is then proposed by developing reconfigurable metasurface loadings implementing continuous-flow microfluidics and digital microfluidics. In the latter technique, a frequency reconfigurable AMC is designed using a pixelized approach with liquid metal interconnects. Simulations show that the pixelized design demonstrates switching by electric actuation between 2.45 GHz and 5 GHz depending on the state of the liquid metal interconnects. On the other hand, a multifunctional reconfigurable metasurface based on liquid metal injection (pressure) is presented. The reflective metasurface formed by two switchable microfluidic layers – top layer comprising an array of meandered half-rings and the lower layer, straight meander lines - can be reconfigured into four polarization states. The proposed metasurface becomes a reflector with emptied channels, whereas exhibits linear to cross polarization conversion (or linear to circular polarization conversion) properties when the top (or bottom) layer is filled with liquid metal alloy. The experimental results confirm the simulation results over the 8 GHz to 12 GHz test band. The compactness, structural flexibility and multifunctionality of the proposed designs make them suitable candidates for modern integrated antenna array systems.