Design and Analysis of Broadband Antenna Array

Abstract

In recent years, the development of broadband array antennas has attracted significant attention due to their crucial role in electronic warfare, satellite communications, and next-generation wireless systems like 5G. In electronic warfare, these antennas enable rapid detection of unknown signals across wideband, enabling fast response to jamming or interference. In satellite communications, they support high-speed, high-capacity data transmission by handling multiple frequencies simultaneously, enhancing performance between ground stations and satellites. Similarly, in wireless communication systems, the ability to process multiple channels concurrently maximizes communication efficiency. This thesis focuses on broadband array antenna design techniques utilizing artificial dielectric slabs suitable for various fields. First, we propose a planar array antenna employing seven artificial dielectric slabs with distinct effective permittivity and impedance, stacked above a bow-tie slot antenna. This configuration achieves a 3:1 bandwidth from 6-18 GHz by arranging the slabs in a linear intrinsic impedance distribution relative to the slot antenna. Each slab is implemented by imprinting sub-wavelength metallic square patches, designed to achieve the desired discrete permittivity. A 12×14 planar array consisting of 8×8 active elements and 80 dummy elements was designed and fabricated, demonstrating active scattering parameters, realized gain, and beamforming patterns steered up to ±45°. Building upon this, we introduce a compact broadband conformal array antenna that achieves 49% size reduction through additional optimization by reducing the number of slabs to three. The antenna features a height of 8.24 mm (0.16λ6GHz) and an array spacing of 8.33 mm (0.5λ18GHz), designed as a conformal array with a curvature of 27.79° in the H-plane. Simulation results confirm that the active scattering parameters remain below -10 dB across the 6 to 18 GHz, with bore-sight gains of -4.88~4.8 dBi across the frequency. To verify performance, we fabricated eight 8×1 array combined in the E-plane, mounted on a curved metallic cylinder. Measurement results show that the active scattering parameters maintain levels below -10 dB, and beam steering errors are within a maximum of 3°. Finally, the thesis presents broadband antenna arrays operating at 6–18 GHz that achieve circular polarization using anisotropic artificial gradient dielectric slabs. These slabs are stacked above a 45° slant linearly polarized bow-tie slot antenna. By introducing different impedance distributions in the x- and y-directions, the slabs exhibit anisotropic properties, enabling circular polarization while maintaining impedance matching. The proposed antenna designs demonstrate significant potential for advancing electronic warfare capabilities, enhancing satellite communications, and improving next-generation wireless systems. By offering broad bandwidth, compact size, and advanced functionalities like conformal mounting and circular polarization, these antennas represent a promising approach to meet the growing demands of modern communication technologies.