Compact Multimode Quadrifilar Helical Antenna for GNSS-R Applications

In this letter, a compact circularly polarized (CP) multimode antenna for global navigation satellite system reflectometry (GNSS-R) is presented. The design comprises two quadrifilar helical antennas (QHAs), each fed with ground coplanar waveguide (GCPW) and quarter wavelength power divider (QWPD) integrated feed. A hybrid staircase-shaped (SSR) QHA radial proposed, it formed by serially arranging several vertical diagonal elements. electric field lines from the elements converge constructively to radiate axis normal. Besides, circular spatial offsets between adjacent induce 90$^{\circ }$ delay in radiated. This shape launches an unprecedented theory facilitating normal mode of operation (MOOp) generates CP over broad elevations azimuths (0$< $$\theta$$\phi$). port-to-port offset GCPW architecture yield high isolation ($>$20 dB). Unlike conventional GNSS-R antennas, (170.5 mm × 132 mm) configuration operates axial mode, offers beam coverage (237), minimizes pattern interference QHAs upon gap-free stacking, ensures accuracy remote sensing data computed. Additionally, supports proficient (efficiency$>$0.9) multiconstellation sensing. prototype was fabricated measured, measurements agreed well simulations.