Superdirective Antenna Pairs for Energy-Efficient Terahertz Massive MIMO

TL;DR

This paper introduces a novel superdirective antenna array design for THz massive MIMO systems that significantly improves energy efficiency by reducing hardware complexity while maintaining high data rates.

Contribution

The paper proposes a superdirective array design with nonuniform spacing that leverages mutual coupling, enabling energy-efficient THz massive MIMO with fewer antennas and simplified excitation.

Findings

Achieves high energy efficiency gains over traditional arrays.

Reduces the number of antennas needed without sacrificing data rate.

Demonstrates practical implementation of superdirective arrays in THz systems.

Abstract

Terahertz (THz) communication is widely deemed the next frontier of wireless networks owing to the abundant spectrum resources in the THz band. Whilst THz signals suffer from severe propagation losses, a massive antenna array can be deployed at the base station (BS) to mitigate those losses through beamforming. Nevertheless, a very large number of antennas increases the BS's hardware complexity and power consumption, and hence it can lead to poor energy efficiency (EE). To surmount this fundamental problem, we propose a novel array design based on superdirectivity and nonuniform inter-element spacing. Specifically, we exploit the mutual coupling between closely spaced elements to form superdirective pairs. A unique property of them is that all require the same excitation amplitude, and thus can be driven by a single radio frequency chain akin to conventional phased arrays. Moreover, they facilitate multi-port impedance matching, which ensures maximum power transfer for any beamforming angle. After addressing the implementation issues of superdirectivity, we show that the number of BS antennas can be effectively reduced without sacrificing the achievable rate. Simulation results demonstrate that our design offers huge EE gains compared to uncoupled arrays with uniform spacing, and hence could be a radical solution for future THz systems.