Design and Evaluation of a Quadrifilar Helix Antenna (QHA) for GPS Anti-Jamming Performance Assessment in Urban Vehicular Environments

This paper presents the design, simulation, and implementation of a circularly polarized Quadrifilar Helix Antenna (QHA) as a passive solution to mitigate electromagnetic interference (jamming) in GNSS systems. The study aims to enhance the reception of GPS L1 signals (1.575 GHz) through an optimized right-hand circularly polarized (RHCP) antenna and to evaluate its performance against a conventional linearly polarized patch antenna. The analysis focuses on the Carrier-to-Noise Density Ratio (C/No), which reflects the quality of the received signal. To validate the proposed design, comprehensive electromagnetic simulations were conducted using CST Studio Suite 2025, followed by experimental testing under active jamming conditions. The results indicate that the QHA provides superior signal stability and preserves 3D Fix positioning continuity more effectively than the patch antenna under interference. Once the jammer is activated, the C/No of the patch antenna drops to approximately 0 ~ d B - H z, ~ w h i l e ~ t h e ~ Q H A ~ m a i n t a i n s ~ v a l u e s ~ n e a r ~ 3 5 ~ d B - H z. This result confirms its substantially higher resistance to jamming.