Diversity Limits of Compact Broadband Multi-Antenna Systems

TL;DR

This paper investigates how mutual coupling in compact multi-antenna systems affects bandwidth, revealing that coupling creates diverse eigen-modes with implications for system design and optimization.

Contribution

It demonstrates that mutual coupling generates eigen-modes with distinct frequency responses and discusses how communication techniques like Diversity-OFDM must be adapted accordingly.

Findings

Mutual coupling creates eigen-modes with diverse frequency responses.

Optimal matching can reduce bandwidth at the center frequency.

Communication techniques need optimization to address coupling effects.

Abstract

In order to support multiple antennas on compact wireless devices, transceivers are often designed with matching networks that compensate for mutual coupling. Some works have suggested that when optimal matching is applied to such a system, performance at the center frequency can be improved at the expense of an apparent reduction in the system bandwidth. This paper addresses the question of how coupling impacts bandwidth in the context of circular arrays. It will be shown that mutual coupling creates eigen-modes (virtual antennas) with diverse frequency responses, using the standard matching techniques. We shall also demonstrate how common communications techniques such as Diversity-OFDM would need to be optimized in order to compensate for these effects.