Star-patterned FSS-assisted multi-step notched antenna for enhancing circular polarization, gain, and impedance matching
Abstract
Conventional FR4 substrates have high frequency problems, with polarization capability and performance deterioration being major challenges in its design. To overcome these limitations, this article describes a multi-step notched antenna that is combined with a star-shaped Frequency Selective Surface (FSS) in order to demonstrate better electromagnetic performance at a higher frequency. Although FR4 exhibits higher dielectric loss at X-band frequencies, it was selected for its low cost, easy fabrication, and practical prototyping advantages. The standalone FR4-based antenna achieves a gain of 3.77 dBi, while the integration of the star-patterned FSS improves the gain to 7.31 dBi by enhancing broadside field reinforcement and reducing backward radiation. Therefore, the reported gain improvement is attributed to the FSS-assisted radiation enhancement rather than the FR4 substrate alone. The proposed antenna resonates at 9.8 GHz and has a reflection coefficient of -38.4dB with an attained gain of 3.77dB. In order to improve the antenna performance even more, unit cell FSS is used in form of a star shape and its dimensions measure 1.44λ0 × 1.44λ0 × 1.6 mm3. The FSS integration leads to a high degree of improvement such as improved impedance matching, broader angular stability of circular polarization in both principal planes as well as an achieved increase of gain as high as 7.3dB. These findings present the demonstration that the multi-step notch antenna with the FSS integration provides a good solution to X-band applications. Hence, the proposed FSS assisted multi-step notched antenna is mainly designed for compact X-band applications like short-range radar sensing, defence surveillance communication, satellite communication front-end modules, and high gain directional wireless links that demand high gain, impedance matching, radiation efficiency and circular polarization stability.