Fluidic, Solid-State, and Hybrid Reconfiguration Techniques in a Frequency and Polarization Reconfigurable Antenna
This work presents the development of a hybrid reconfiguration technique used to achieve both frequency and polarization diversity in a 2.4 ? 2.5 GHz microstrip antenna. This hybrid solution for the first time combines current state-of-the-art fluidic and solid-state reconfiguration mechanisms in a collaborative effort. Two orthogonally-crossed and co-located narrow microstrip patches with gap discontinuities separating a central probe-fed section from the radiating slots provides the base antenna structure. The fluidic mechanisms use high strength dielectric fluids or liquid metal loaded across the gap discontinuities and the solid-state mechanisms uses readily available RF PIN and varactor diodes integrated across the gaps to enable reconfiguration. Accurate and robust circuit modeling concepts are presented to provide insight on antenna performance and loss mechanisms from each reconfiguration technique.
A polarization-only reconfigurable version of this antenna utilizing dielectric fluids, RF PIN didoes, and liquid metal in separate design iterations were examined to introduce design and circuit modeling concepts and provide a first comparison between the reconfiguration techniques. While all iterations achieved good linear polarization switching, dielectric fluids and the RF PIN didoes are found to have large negative impacts on radiation performance due to ohmic losses (radiation efficiencies between 8 ? 35%). In the liquid metal iteration, ohmic losses are significantly reduced to boost radiation efficiencies near that of a tradition patch antenna (near 80%).
The hybrid reconfiguration solution utilizes liquid metal and solid-state varactors for polarization and frequency diversity, respectively. Non-hybrid design iterations using only dielectric fluids and solid-state RF PIN diodes with varactors provide a comparison between all reconfiguration techniques and demonstrate the advantages of the hybrid solution. It was found that broadly variable dielectric strength fluids used as a sole reconfiguration mechanism can achieve a wide frequency tuning range of 700 MHz, maintain linear polarization switching, and have radiation efficiencies near 60%. However, the fluids must have loss tangents less than 0.02 and are currently not readily available. The RF PIN and varactor diode combination provides a realizable solution, however, suffers from excessive DC control power requirements, a limited tuning range of 100 MHz, and low radiation efficiency around 16%. The hybrid solution combines the best aspects of all subsequent design iterations to achieve a realizable frequency and polarization reconfigurable antenna with a tuning range of 263 MHz and 41.7% radiation efficiency average across reconfiguration states.