An optically semi-transparent liquid antenna with slot-coupled feeding for future wireless communication systems

To meet the needs of optically transparent camouflage and concealment in the military field, as well as to improve the aesthetics and flexibility of wireless electronic devices. In this paper, a rectangular wideband liquid antenna with medium transparency and a hollowed-out center is proposed. The antenna is fabricated by using 3D printing technology and is primarily composed of a hollowed-out rectangular resin container, a transparent ionic liquid, and a non-transaprent slot-coupled feeding structure. By removing the center of the resin container and filling it with air, a resonator is formed that merges a rectangular ring with air. This method decreases the equivalent relative permittivity of the entire resonator and expands the operating bandwidth. Experimental results show that the antenna has an impedance bandwidth of 7 GHz-8.25 GHz, a relative bandwidth of 16.4%, a optical transparency of 84.57% and a maximum gain of 9.5dBi at 8 GHz. The proposed antenna has potential applications in electronic countermeasures, multimode composite guidance, 5G communication, and transparent electronic devices.