Quasi-Closed-Form Driven Near-Field Flat-Top Beamfocusing with Concentric Circular Vertical Polarized Dipole Array For Large Intelligent Surface Applications

TL;DR

This paper introduces a semi-closed-form method for synthesizing near-field flat-top beams using a concentric circular dipole array, enabling precise beam shaping for large intelligent surface applications.

Contribution

It presents a novel semi-closed-form approach combined with an optimization algorithm for flat-top beam synthesis in near-field scenarios, validated by electromagnetic simulations.

Findings

Circular ring arrays exhibit distinct gain behaviors along the focal region.

Parameter tuning and optimization effectively suppress sidelobes.

The method achieves accurate flat-top beam formation in near-field conditions.

Abstract

This letter presents a near-field flat-top beam synthesis method based on a semi-closed-form approach. First, the feasibility of achieving a flat-top beam in the near field is examined using a closed-form analysis. A circular concentric ring array structure is adopted, and it is observed that circular rings with different radii exhibit distinct gain characteristics along the focal region on the z-axis. Specifically, smaller radii lead to a monotonic increase in electric field strength near the focus, whereas larger radii result in a monotonic decrease. Based on this behavior, parameters such as the number of rings and the initial radius are determined through field superposition. Subsequently, an optimization algorithm is employed to fine-tune the excitation amplitudes of the individual rings in order to suppress sidelobes. The effectiveness of the proposed method is validated through full-wave electromagnetic simulations.