A Compact-Size Wideband Optically-Transparent Water Patch Antenna Incorporating an Annular Water Ring

A wideband optically-transparent water patch antenna with a compact size is proposed. Both the water patch and the water ground plane are made of distilled water to realize the highly optical transparency. Particularly, by simply incorporating an annular water ring under the water patch, the center frequency can be reduced from 2.3 GHz to 1.95 GHz, while the corresponding size of the water patch can be reduced by 28%. Both the simulation and the measurement are carried out for verification. The measured results turn out that a wide impedance bandwidth of 41.8% with SWR < 2, the maximum gain of 1.56 dBi, radiation efficiency up to 78% and stable monopolar radiation pattern with linear polarization can be achieved. Additional, the effects of the annular water ring on the antenna performance are analyzed and discussed.