A Gain-Improvement Method using Mixed Metasurface Superstrate with Channel Capacity Enhancement

A gain-improvement(GI) method using mixed metasurface superstrate for the compact ±45° orthogonal dual-polarized base station antenna array is proposed in this article. The method consists of two metasurface-superstrates, the high permittivity ceramic lens (HPCL) and the high refractive-index surface (HRIS) for ±45° polarizations. The HPCL adjusts the phase distribution of radiated waves of every antenna in the array to form a quasi-plane wavefront and the HRIS refracts the waves to further form a nearly planar wavefront to achieve GI. Moreover, the GI method doesn’t affect impedance match of the antenna array and the realized gain of the array improves. Two GI examples, including the GI of a 1 x 3 subarray and the GI of a 4 x 3 array, are presented. The measured peak realized gain of the 4 x 3 array is enhanced by up to 2dBi and the array achieves a measured realized aperture efficiency(RAE) up to 90% within 1.71-2.17GHz band. The GI method brings the increase up to 22% of the channel capacity of a 4 x 4 MIMO system. The above improvement allows a 4 x 3 array to be used, instead of a 4 x 4, which results in a 25% aperture reduction. The attracted features of this method make it a key candidate technology for future mobile communications for a massive MIMO application.