Fundamental bounds on MIMO antennas

TL;DR

This paper establishes fundamental capacity bounds for MIMO antennas using current optimization, demonstrating how to maximize spectral efficiency under fixed Q-factor and efficiency constraints through semi-definite programming.

Contribution

It formulates a novel optimization framework for MIMO antenna capacity bounds considering physical constraints, employing model order reduction for computational efficiency.

Findings

Derived capacity bounds for MIMO antennas with physical constraints.

Implemented semi-definite optimization for practical antenna geometries.

Showed effectiveness of model order reduction in complex optimization problems.

Abstract

Antenna current optimization is often used to analyze the optimal performance of antennas. Antenna performance can be quantified in e.g., minimum Q-factor and efficiency. The performance of MIMO antennas is more involved and, in general, a single parameter is not sufficient to quantify it. Here, the capacity of an idealized channel is used as the main performance quantity. An optimization problem in the current distribution for optimal capacity, measured in spectral efficiency, given a fixed Q-factor and efficiency is formulated as a semi-definite optimization problem. A model order reduction based on characteristic and energy modes is employed to improve the computational efficiency. The performance bound is illustrated by solving the optimization problem numerically for rectangular plates and spherical shells.