Wideband 1 × 2 tree-shaped fractal antenna array with gain enhancement and sidelobe level reduction for sub-6 GHz 5G applications

This research presents a wideband (WB) 1 × 2 tree-shaped fractal antenna (TFA) array designed for sub-6 GHz 5G applications, featuring sidelobe level (SLL) reduction and gain enhancement. The array consists of two linearly arranged TFAs combined with a Wilkinson power divider (WPD) using a single-feed configuration. The WPD is selected due to its wide bandwidth, strong suppression factor, compact size, simple structure, excellent port isolation, and low insertion loss. A single TFA element, fabricated on a Rogers RT5880 substrate with a relative permittivity of 2.2 and a thickness of 1.57 mm, has dimensions of 38.5 × 49.5 mm 2 . It operates from 2.2 GHz to beyond 5 GHz, achieving a gain of 2.2–4.5 dBi. The proposed 1 × 2 array layout measures 76.5 × 81.36 mm 2 and employs defected ground structure (DGS) and stub-loading techniques to suppress SLL and enhance gain. The array achieves a reflection coefficient better than –25 dB and an SLL of –13.2 dB. At the resonance frequency of 3.5 GHz, the gain improves significantly, rising from 3.2 dBi (single element) to 7.5 dBi (array). Simulated and experimental results confirm excellent agreement, validating the effectiveness of the proposed design.