Design and Beamforming Performance of the Compact ESPAR Antenna for the Beam Space MIMO System

Abstract

Multiple-input multiple-output (MIMO) system is essential to wireless and mobile communication for the higher channel capacity. However, this MIMO system requires many active RF (radio frequency) stages, and is very difficult to be used in mobile devices. It produces the high energy consumption at RF stage as well as the high hardware complexity. Especially, it will be more serious in the massive MIMO system that is strongly considered as an enabling technology for the 5G mobile communication system. In order to solve this problem, beam-space MIMO (BS-MIMO) systems were proposed using the electronically steerable parasitic array radiator (ESPAR) antenna, which work as the MIMO system using single RF stage with many passive parasitic elements. However, there are some limits in this ESPAR based BS-MIMO system because of this many passive parasitic elements. The conventional BS-MIMO system basically uses two parasitic elements for one dimension of MIMO. So, in this paper we like to propose a design method for reducing the passive elements number in this BS-MIMO system. In the proposed system, we cut down the number of the parasitic elements into half. So, the proposed BS-MIMO system uses one parasitic element for one dimension of MIMO. To design 8 ? 8 MIMO system, only eight elements of parasitic elements are needed instead of 16 elements in conventional design. Since this proposed ESPAR based BS-MIMO system requires only the half number of parasitic elements, we can design more compact ESPAR antenna design. Also, we can easily increase the MIMO dimension with compact size by this proposed ESPAR antenna. Simulation results can confirm that the proposed ESPAR BS-MIMO system with half number of elements keeps the very similar performance of the conventional system and acceptable beamforming performance as well. This proposed system could be very useful for the massive MIMO system design for the 5G mobile communication.