Selective Excitation of Characteristic Modes on an Electrically Large Antenna for MIMO Applications

Abstract

The selective excitation of individual characteristic modes for MIMO applications on an electrically large antenna structure is investigated. The characteristic mode analysis yields that a large number of modes is significant and thus basically suited for use in a multi-mode antenna. In order to find appropriate excitation arrangements for the individual characteristic modes, they are grouped according to their symmetry properties. It is found that characteristic currents belonging to the same group are correlated and thus cannot be excited separately, resulting in a reduced set of uncorrelated antenna ports.

On the Feasibility of Multi-Mode Antennas in UWB and IoT Applications below 10 GHz

“…The achievable gain is represented by Fig. 4, curve (6). It is shown that by combining the ports of the antenna and using constructive interference, an additional gain of up to two decibel can be achieved.…”

“…The number of significant modes depends on the electrical size of the antenna. As another example, the chassis of a typical modern smart phone is electrically large in the frequency range from 6 GHz to 8.5 GHz and thus exhibits a large number of significant characteristic modes, offering a great diversity potential [6].…”

Single-Element Beamforming using Multi-Mode Antenna Patterns

“…Towards UWB and multi-mode capability, an electrically large aperture is necessary to enable different current distributions at the same time. As the feeding network connects feeding points and antenna input ports in a sophisticated manner [5], [6], each physical port corresponds to a unique group of modes, which can be excited. Since the groups of modes are orthogonal among each other, the ports are uncoupled.…”

“…In the numerical results presented below, focus will be on the planar multi-mode antenna design presented in [5], [6]. So far, this antenna type has been investigated for communication and localization purposes.…”

Preliminary Study on Differences between Full- and Sub-Structure Characteristic Modes

“…A suitable choice of significant CMs and their excitation method can yield antenna designs that meet tough requirements, e.g., [3]. However, electrically large structures lead to large mesh sizes and large increases in the number of significant modes [4]. Thus, CM analysis (CMA) of the full structure is not only computationally demanding, but more importantly the cost is high for finding a subset of modes that are relevant for the antenna design problem at hand.…”