Effects of metallic caps for liquid metal in substrate integrated waveguide antenna

A frequency-switchable half-mode substrate integrated waveguide (HMSIW) antenna with different cases of metallic caps is proposed. The resonant frequency of the HMSIW antenna is widely switched when liquid metal (eutectic gallium indium; EGaIn) is injected into a single vertical fluidic hole. The position and dimensions of the fluidic hole are chosen in order to maximize the tuning range and peak gain. The radiation performance of the antenna is demonstrated through full-wave simulation and measurement. The resonant frequency is successfully switched from 2.33 to 3.35 GHz by injecting EGaIn into the vertical fluidic hole while maintaining the peak gain higher than 6 dBi.