[Paper Review] Design of a Planar Eleven Antenna for Optimal MIMO Performance as a Wideband Micro Base-station Antenna

Aidin Razavi, Wenjie Yu+2 more|arXiv (Cornell University)|Apr 16, 2018

Antenna Design and Analysis10 references3 citations

TL;DR

This paper presents a low-profile planar Eleven antenna optimized for 2-, 4-, and 8-port MIMO operation in micro base-stations across 1.6–2.8 GHz. Using genetic algorithm optimization, it achieves high MIMO efficiency in both Random-LOS and RIMP environments, with 4-port mode delivering the best performance due to improved diversity and embedded efficiency.

ABSTRACT

A new low-profile planar Eleven antenna is designed for optimal MIMO performance as a wideband MIMO antenna for micro base-stations in future wireless communication systems. The design objective has been to optimize both the reflection coefficient at the input port of the antenna and the 1-bitstream and 2-bitstream MIMO efficiency of the antenna at the same time, in both the Rich Isotropic MultiPath (RIMP) and Random Line-of-Sight (Random-LOS) environments. The planar Eleven antenna can be operated in 2-, 4-, and 8-port modes with slight modifications. The optimization is performed using genetic algorithms. The effects of polarization deficiencies and antenna total embedded efficiency on the MIMO performance of the antenna are further studied. A prototype of the antenna has been fabricated and the design has been verified by measurements against the simulations.

Motivation & Objective

• Address the need for low-profile, wideband, multi-port MIMO antennas in future 5G micro base-station deployments.
• Optimize both input return loss (reflection coefficient) and MIMO efficiency across 1.6–2.8 GHz for enhanced system-level performance.
• Evaluate performance in realistic edge environments—Random-LOS and RIMP—since real-world conditions lie between these extremes.
• Investigate the impact of polarization deficiencies and total embedded efficiency on MIMO coverage and system throughput.
• Demonstrate feasibility of operating the same planar Eleven structure in 2-, 4-, and 8-port modes with minimal structural changes.

Proposed method

• Employ genetic algorithms to simultaneously optimize reflection coefficient and 1-bitstream/2-bitstream MIMO efficiency across the 1.6–2.8 GHz band.
• Design a planar, dual-polarized Eleven antenna with two orthogonal branches in separate planes to support dual-polarization diversity.
• Use ViRM-lab software to simulate system-level MIMO performance in both Random-LOS and RIMP environments with arbitrary incident waves.
• Define and analyze polarization deficiencies using amplitude imbalance (Iₐ) and polarization correlation (Iₚ) metrics to quantify spatial MIMO coverage degradation.
• Fabricate a prototype and validate simulation results through measurement-based verification in both RIMP (reverberation chamber) and Random-LOS (anechoic chamber) setups.
• Assess total embedded efficiency of each port in 2-, 4-, and 8-port modes to link hardware performance to MIMO efficiency.

Experimental results

Research questions

• RQ1 How does the planar Eleven MIMO antenna perform in terms of MIMO efficiency across 1.6–2.8 GHz in both Random-LOS and RIMP environments?
• RQ2 What is the impact of polarization deficiencies (Iₐ and Iₚ) on the spatial distribution of MIMO coverage and system-level performance?
• RQ3 How does increasing the number of ports (2, 4, 8) affect MIMO efficiency, and what role does total embedded efficiency play in this trade-off?
• RQ4 Can the same planar Eleven structure be effectively reconfigured for 2-, 4-, and 8-port operation with minimal modifications?
• RQ5 Does the 4-port mode offer a performance advantage over 2- and 8-port modes in terms of MIMO efficiency and system robustness?

Key findings

• The 4-port mode achieves the highest MIMO efficiency across the 1.6–2.8 GHz band, outperforming both 2-port and 8-port configurations due to better diversity and lower correlation.
• The 8-port mode suffers from degraded MIMO efficiency due to low total embedded efficiency and suboptimal impedance matching, despite increased port count.
• Polarization deficiencies (Iₐ and Iₚ) are highest at 1.6 GHz and 2.8 GHz, leading to reduced MIMO coverage and increased power requirements for 95% Probability of Detection.
• Measured results closely match simulations, validating the design and optimization methodology in both RIMP and Random-LOS environments.
• The 2-port mode maintains acceptable MIMO efficiency with low variation across the band, but offers less diversity gain than the 4-port configuration.
• The planar structure enables simple manufacturing and wall-mounting suitability, making it ideal for low-profile micro base-station applications.