Rotatable Coupler Antenna Enhanced Wireless Network: Modeling and Coupler Rotation Optimization

2026-05-19

AI Summary

This work addresses the challenge of enhancing wireless communication performance while simultaneously reducing the number of radio frequency (RF) chains and active antennas. To this end, the authors propose a mechanical beamforming architecture based on a three-dimensional passively coupled rotatable coupler. The system operates without additional RF chains; leveraging multiport circuit theory, they formulate a channel model and cast the coupler rotation optimization as a constrained non-convex problem. An efficient solution is achieved by integrating a spherical cap conditional gradient algorithm with the cross-entropy method. Simulation results demonstrate that the proposed approach significantly outperforms existing benchmarks in terms of received signal-to-noise ratio and overall communication performance, all while substantially lowering hardware complexity.

Abstract

Flexible coupler antenna systems have recently received significant research interest due to their capability to intelligently reconfigure wireless channels by controlling coupler positions and/or rotations and dynamically exploiting mutual coupling. In this paper, we investigate a new type of flexible coupler antenna, termed rotatable coupler antenna (RCA), for enabling spectrum and energy efficient wireless communication cost-effectively. Specifically, an RCA consists of one fixed active antenna and multiple low-cost passive couplers, each of which can independently rotate in three-dimensional (3D) space, so as to collaboratively achieve mechanical beamforming without requiring additional radio-frequency (RF) chains for the couplers. We study an RCA-enhanced point-to-point communication system, where one RCA is deployed at the transmitter to serve a single user equipped with a fixed antenna. Based on multi-port circuit theory, we establish the channel model and characterize the mutual coupling coefficients as a function of coupler rotations. We formulate a new problem to maximize the received signal-to-noise ratio (SNR) at the user by optimizing the 3D rotations of all couplers, subject to practical coupler rotation constraints. To tackle this nonconvex problem, we develop a spherical-cap conditional-gradient-based algorithm with cross-entropy-method initialization. Simulation results demonstrate that the proposed RCA system can significantly improve communication performance in comparison with benchmark schemes, while requiring substantially fewer active antennas and RF chains.

Problem

• rotatable coupler antenna
• mutual coupling
• mechanical beamforming
• SNR maximization
• 3D rotation optimization

Innovation

• rotatable coupler antenna
• mechanical beamforming
• mutual coupling optimization
• 3D rotation control
• RF-chain-free design