Effects of Concentration, Temperature and Geometry on Double Spiral Liquid Orbital Angular Momentum Antenna

This paper studies the relationship between liquid concentration, temperature and geometry and the performance of the double spiral liquid orbital angular momentum (OAM) antenna which has two nested spiral shells to excite multiple OAM modes. Distilled water and salt water are injected into the inner and outer spiral shells, respectively. Attractive simulation and measurement results are obtained by changing the concentration and temperature of injected solution and the radius of spiral shells. The bandwidth will increase 100 MHz by the geometry decreases, the center frequency will shift 500 MHz by the liquid temperature, and the radiation efficiency will improve 20% by the liquid concentration. The proposed double spiral liquid OAM antenna can generate OAM models of l = 1 and l = 3at 1.65 GHz and 5.4 GHz.