Fei Wang

A dual-polarized Fabry-Pérot (FP) antenna with ultra-wideband radar cross section (RCS) reduction using 3D printing technology is proposed. The proposed antenna consists of a dual-polarized primary antenna and a partially reflective surface (PRS) loaded with reflective surface (RS) and 3D-printed stepped absorbing structure (3D-PSAS). The combination of the RS and the 3D-PSAS effectively reduces the RCS of the FP antenna and maintains the gain of the antenna. Meanwhile, the proposed antenna can be used in the construction of stealth systems. Both the simulated results and the measured results verify the reliability of the design. The FP antenna owns 10-dB RCS reduction bands cover 3.0∼3.8 GHz and 6∼15 GHz, with a peak RCS reduction of 27 dB at 12.5 GHz. In the radiation, it owns a 10-dB return-loss bandwidth of 4.64–5.64 GHz (19.4%) and 4.76–5.61 GHz (16.3%) respectively in X polarization and Y polarization modes, with a maximum realized gain of 12.4 dBi at 4.9 GHz.

Microwave-absorbing structures are increasingly vital for applications such as electromagnetic protection, stealth technology, and wireless communications. However, their broader adoption is often limited by drawbacks such as excessive thickness, narrow absorption bandwidth, and high manufacturing costs. This study presents the design, fabrication, and evaluation of a sunflower-inspired metastructure for broadband microwave absorption, achieved via fused deposition modeling three-dimensional printing. The metastructure, inspired by the spiral geometry of sunflower seed arrangements, integrates multi-layered, gradient spiral elements composed of carbon black-carbonyl iron powder/polylactic acid (CB-CIP/PLA) composites. Electromagnetic simulations were employed to systematically optimize key structural parameters, including the gradient impedance increment and individual layer thicknesses, to maximize absorption efficiency. Both simulated and experimental results demonstrate that the absorber achieves an effective absorption bandwidth of 12.13 GHz (5.87 – 18.00 GHz) with reflection loss below 10 dB, covering the C, X, and Ku frequency bands. The performance is attributed to the synergistic effects of interfacial polarization and natural magnetic resonance within the CB-CIP/PLA composite. The metastructure also exhibits stable, wide-angle absorption properties, maintaining bandwidths exceeding 10 GHz for incident angles up to 50° under both transverse electric and transverse magnetic polarizations. The proposed sunflower-inspired design demonstrates significant advantages in bandwidth-to-thickness ratio, fabrication efficiency, and polarization insensitivity compared to conventional biomimetic absorbers. These findings highlight the promise of bio-inspired design strategies for developing lightweight, efficient, broadband microwave absorbers, providing valuable reference for future advancements in the field.

Electromagnetic (EM) wave absorption performance is greatly affected by the microscopic morphology of the absorbing material particles. In this study, a facile and efficient ball-milling method was applied to increase the aspect ratio of particles and prepare flaky carbonyl iron powders (F-CIPs), one of the most readily commercially available absorbing materials. The effect of ball-milling time and rotation speed on the absorption behaviors of the F-CIPs was investigated. The microstructures and compositions of the F-CIPs were determined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The EM parameters were measured using a vector network analyzer (VNA) in the frequency range of 2–18 GHz. The results indicated that the ball-milled flaky CIPs exhibited a better absorption ability than the raw spherical CIPs. Among all the samples, the sample milled at 200 r/min for 12 h and the sample milled at 300 r/min for 8 h showed remarkable EM parameters. The ball-milling sample with 50 wt.% F-CIPs had a minimum reflection loss peak of −14.04 dB at a thickness of 2 mm and a maximum bandwidth (RL < −7 dB) of 8.43 GHz at a thickness of 2.5 mm, a result that conformed with the transmission line theory. Hence, the ball-milled flaky CIPs were considered to be beneficial for microwave absorption.

To prepare lightweight, wideband, strong absorption and low-cost microwave absorbing materials, carbon black/polylactic acid (CB/PLA) composite filaments were prepared using a high-energy mixer and twin-screw extruder. Coaxial ring test pieces were printed by fused filament fabrication (FFF) technology with polylactic acid as the matrix and carbon black as the absorbent. The crystal texture and micromorphology of the composites were observed by XRD and SEM. The electromagnetic parameters were measured at 2–18 GHz using a vector network analyzer. The influence of CB content on the absorbing performance of the composites was studied, and the loss mechanism was explained. The results show that when the CB content (refers to PLA) is 25%, the composite has suitable impedance matching, conduction loss, and polarization loss, resulting in the best microwave absorption performance. The minimum reflection loss reached −45.47 dB at 13.68 GHz, and the corresponding effective absorption bandwidth was 5.36 GHz (10.72–16.08 GHz) with a matching thickness of 2.1 mm. At the same time, the density of the composite was only 1.19 g/cm³. This work sheds light on the development of lightweight and high-efficiency microwave absorption materials (MAMs) in a simple and low-cost manner.

A single microwave absorbent and simple coating structure cannot meet the increasing requirements for broadband and strong absorption. Three-dimensional printing is an effective way to prepare multi-component complex structure metamaterial absorbers, and the key is to prepare raw materials with excellent absorption properties, suitable for 3D printing. In this paper, CB-CIP/PLA composite filament was prepared via a high-energy mixer and twin-screw extruder by compounding the dielectric loss material carbon black (CB) and the magnetic loss material carbonyl iron powder (CIP) with polylactic acid (PLA) as the matrix. The coaxial ring test piece was printed by FDM technology, and the microstructure of the composites was observed and analyzed by SEM. Meanwhile, the electromagnetic parameters of the composites were examined by a vector network analyzer, mainly studying the influence of the CB and CIP content and thickness on the microwave absorbing properties of the composite material. The results show that when the CB content is 20% and the CIP content is 30%, the CB-CIP/PLA composite has excellent microwave absorption and broad bandwidth. When the matching thickness is 1.6 mm, the minimum reflection loss (RL) reaches −51.10 dB; when the thickness is 1.7 mm, the effective absorption bandwidth (RL < −10 dB) is 5.04 GHz (12.96–18 GHz), nearly covering the whole Ku band. This work provides an efficient formulation and process to prepare an absorbing composite filament for FDM.