Fabry-Perot cavity-based circularly polarized Sierpinski fractal antenna with analysis and measurement characterization for sub 5/6G V2I and V2V communication

This paper presents the design, fabrication, and performance analysis of a high-gain, broadband circularly polarized (CP) Fabry-Perot cavity (FPC) antenna tailored for vehicular communication applications. The proposed antenna employs a frequency-selective surface (FSS)-based partially reflective surface (PRS) superstrate, fabricated on Rogers 5880 substrate, to enhance gain and 3-dB gain bandwidth. At the core of the design is a Sierpinski fractal-shaped radiating element with corner etching, which effectively addresses the narrow axial ratio (AR) bandwidth limitations typically associated with circularly polarized (CP) antennas. The single-element configuration yields a gain of 3.8 dBc, which increases to 7 dBc in a two-element array arrangement. Integrating a Fabry-Perot configuration with a single PRS superstrate of 1.575 mm thickness and positioned 24.6 mm above the radiating patch further improves the performance, achieving 15.5 dBc gain and enhanced AR bandwidth centered around 5.9 GHz. To further augment the performance, a PRS with a positive phase gradient is introduced, resulting in a stable peak gain of 17.72 dBc and improved beam width and polarization stability. Comprehensive simulations and measurements show excellent agreement, validating the proposed antenna's suitability for high-performance, real-world vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), and vehicle-to-everything (V2X) communication systems.