Directivity Enhancement of Movable Antenna Arrays with Mutual Coupling

2026-03-17

AI Summary

This work proposes an innovative approach to harness mutual coupling—typically regarded as detrimental in conventional antenna arrays—as a means to enhance far-field directivity in specific directions. By strategically optimizing the positions of movable antenna elements, mutual coupling is actively exploited rather than mitigated, transforming it from a source of interference into a performance-enhancing mechanism. To achieve this, a low-complexity optimization algorithm combining greedy search with gradient descent (GS-GD) is developed: an initial layout is selected over a discrete grid via greedy search, followed by fine-tuning through continuous position adjustments using gradient descent. Experimental results demonstrate that the resulting array configuration significantly outperforms traditional uncoupled uniform linear arrays across omnidirectional coverage, with the GS-GD algorithm achieving near-global-optimal directivity gains in most directions.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Machine Learning: Optimization
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web

Abstract

In conventional antenna arrays, mutual coupling between antenna elements is often regarded as detrimental. However, under specific conditions, it can be harnessed to enhance the far-field directivity (i.e., beamforming gain). Theoretically, the directivity of an N-antenna superdirective array over the endfire direction can reach N^{2}, significantly exceeding the directivity of a traditional uncoupled array which is N over all directions. This paper investigates the potential of mutual coupling effects in movable antenna (MA) arrays for directivity enhancement. A low-complexity algorithm called Greedy Search and Gradient Descent (GS-GD) is proposed to optimize the antenna positions for maximizing the array directivity over any given direction, where the antenna positions are first selected sequentially from discrete grid points and then continuously refined through gradient descent (GD) optimization. Numerical results demonstrate that the optimized MA array design by exploiting the antenna coupling achieves significant directivity gains compared to the conventional uniform linear array (ULA) without antenna coupling over all directions. Additionally, the proposed GS-GD algorithm is shown to approach the global optimum closely in most directions.

Problem

• mutual coupling
• directivity enhancement
• movable antenna arrays
• superdirective array
• beamforming gain

Innovation

• mutual coupling
• movable antenna array
• directivity enhancement
• superdirectivity
• GS-GD algorithm