Compact Swastik-Slot Loaded Circularly Polarized Antenna with Defected Ground Structure for Wideband C/X/Ku-Band Applications

Abstract

This research proposes a novel multiband circularly polarised microstrip antenna based on a Swastika-shaped slot and a defected ground structure (DGS). The antenna is implemented on Rogers RT Duroid 5880 substrate measuring 45 × 45 × 1.6 mm³, using a 50 Ω microstrip feed line. The antenna design development process starts with a classical circular patch antenna. It is then modified in stages by inserting a Swastik slot, circular perturbation slots, and a DGS to realise multiband behaviour and increase the impedance bandwidth. In addition, a 45-degree rotation of the Swastik slot is added to produce circular polarisation through orthogonally excited modes. The antenna proposed is resonates at 6.5 GHz, 10.26 GHz, 14.75 GHz, and 25.75 GHz with reflection coefficients below −14 dB. The realised impedance bandwidths are 1.57 GHz, 2.78 GHz, 4.0 GHz, and 3.5 GHz, respectively. Also, an axial ratio of 0.31 dB with a 3-dB axial ratio (AR) bandwidth of 610 MHz is achieved at 6.25 GHz. The antenna offers stable radiation patterns, with gains ranging from 6.4 dBi to 7.6 dBi across the operating bands. The fabricated prototype was experimentally characterized, and the measured results are presented to validate the simulated performance of the proposed antenna. Due to its small physical dimensions, multiband operation, and generation of circular polarisation, the antenna proposed is a good choice for satellite communications, radar, and advanced wireless communication systems in the C, X, and Ku bands.