Polyaniline nano-material backed lens antenna for X-band LEO satellite transceivers

Abstract

Abstract This paper presents the design and implementation of an open-ended waveguide lens antenna engineered to generate a conical-shaped radiation pattern for the X-band fully-duplex communication subsystem of a low Earth orbit (LEO) satellite dedicated to Earth remote sensing. The antenna is designed to maintain reliable links with ground stations at a minimum satellite elevation angle of 10°, corresponding to ± 63° off-nadir, for a near-circular orbit at an altitude of 700 km. Operating within the 9.75–10.25 GHz band, the antenna provides broad coverage over a working sector of approximately 126° × 126° in azimuth and elevation, with peak radiation directed at ± 63° from nadir. It achieves a minimum gain of 5 dBic in these directions and employs right-hand circular polarization (RHCP) for downlink and left-hand circular polarization (LHCP) for uplink. The axial ratio remains below 3 dB across the working sector at the center frequency of 10 GHz, while the input reflection coefficient stays better than − 10 dB over a wide impedance matching bandwidth of 8.75–11.25 GHz. The 3-dB axial ratio bandwidth spans from 9.75 to 10.25 GHz. To further enhance performance particularly circular polarization purity, gain, and axial ratio bandwidth a metallic circular backing plate coated with a polyaniline (PANI) nano-material absorber is integrated between the dielectric lens and the reflector disc. The PANI layer, characterized by tunable dielectric properties and intrinsic microwave loss, improves impedance matching at the lens–waveguide interface and effectively suppresses surface currents and backward radiation. Material characterization via X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirms the semi-crystalline structure and micro-porous morphology of the synthesized PANI, which contribute to enhanced electromagnetic absorption. As a result, the axial ratio at 10 GHz is reduced from 1.0 dB to 0.05 dB, the gain at ± 63° is increased from 4.1 dBic to 6.0 dBic, and the 3-dB axial ratio bandwidth is expanded from 400 MHz to 500 MHz. These findings demonstrate the potential of integrating functional PANI nano-materials into high-performance antenna architectures for advanced satellite communication and Earth observation applications.