A Fully Transparent Wideband Water Patch Antenna With L-Shaped Feed

A wideband and fully optically-transparent water patch antenna is proposed. Both the patch and the ground plane are made of distilled water. Different from the previous water patch antennas, this proposed design features the utilization of an L-shaped distilled water probe as the feed structure. Thus, substantial improvement in the transparency is achieved. To excite the water patch antenna, a short inner probe of a coaxial cable is inserted into the water probe. The electromagnetic (EM) waves excited by the inner probe can propagate along the L-shaped water probe and also resonant in the middle substrate (air) under the water patch, causing radiation into the free space. The L-shaped water probe can significantly improve the impedance bandwidth, which has the same function as the reported L-shaped metallic probe. The results show that the proposed water patch antenna has a wide impedance bandwidth of 42.6% (from 1.48 to 2.28 GHz with
$|{\mathrm{ S}}_{11}| < - 10$
dB), a gain up to 7.5 dBi, a radiation efficiency up to 67% and broadside radiation pattern across the bandwidth. In addition, some parametric studies on the distilled water probe have been carried out for the design purpose. The proposed water patch antenna has confirmed the possibility of designing a patch antenna fully made of liquid or solid dielectric materials with high dielectric constant such as water, instead of using metal.