Gigabit per second data transfer at 60GHz in high gain grid antennas

A significant issue in the field of metamaterials is the demonstration of their usefulness in actual communication systems. This paper uses the known grid structure [1-3] as a highly directive superstrate, suspended over a patch antenna, to transfer high data rate signals. The design frequency is at 60 GHz, where worldwide there is several GHz of available unlicensed bandwidth. We measure the system gain of the antenna, and demonstrate its operation with a multi-gigabit per second signal. The grid antenna has been described as having a near zero index of refraction, however, the grid can also be viewed as an antenna aperture. Fundamental limits on the antenna directivity dictate that the maximum directivity which can be achieved for this structure would be limited by the overall size of the grid, i.e., if the physical area of the aperture is A, then D_max = 4 piA/lambda². Therefore, in order to increase the directivity even more, the grid size needs to be increased. In our simulations, an 11 x 11 grid showed the most gain, having over 17 dBi. This structure is shown in Fig. 1. Beyond this size, the patch can no longer efficiently illuminate the grid. If the grid size needs to be increased further in order to increase the gain, one might ask why we simply do not just use an array of patches. The answer lies in the high loss of the substrate at millimeter-wave frequencies. A microstrip array of patch antennas would employ some type of feed network, which becomes very lossy with increasing array size. As a result, large patch arrays are generally not desirable at millimeter-wave frequencies.