A Large-Scale High-Gain Transparent Grid Array Antenna for Millimeter-Wave Communication

A large-scale, high-gain, high-efficiency, optically transparent grid array antenna operating at millimeter-wave frequencies is proposed in this letter. The grid is employed to mitigate the feeding network loss caused by a lossy transparent conductor, which is composed of a series of rectangular loops directly connected to its neighbors rather than connected through a feeding network. The antenna adopts dual ports and achieves a synthetic gain by anti-phase feeding. By loading rectangular patches on the radiators of the outer region, the radiation and impedance characteristics are improved. A large-scale (5.4 lambda x 5.1 lambda x 0.04 lambda at 25 GHz) array was fabricated using a transparent metal mesh with a sheet resistance of 0.25 Omega/sq. A peak gain of 18.18 dBi, radiation efficiency of 59.6% and optical transparency of 84% were obtained. This antenna provides a valuable solution for large scale optically transparent microstrip array antennas.