Tunable and flexible liquid spiral antennas

A cylindrical spiral liquid antenna and a tapered helical water antenna are presented. Saline water with a concentration of 3.5% is injected into a flexible tube to form the radiation structure. Thresholds for changes of the radiation direction are calculated to be 0.1 and 0.4 for the ratio between the spiral diameter and the wavelength. Resonance frequency increases when the probe length or the radius of the vertical liquid decreases. The quantity of the water could be changed with the help of a syringe to enable the reconfigurability. Measurement results show fairly good agreements with that simulated.