Compact Helical Antenna With Counter-Wound Structures for 5G-NR Applications

This paper presents a novel dual-linearly-polarized quadrifilar helix antenna (DLP-QHA) with high cross-polarization discrimination (XPD) and high isolation. The antenna comprises four helical arms, each consisting of a pair of counter-wound half-turn helices. Two opposite arms are excited with differential feeding, resulting in linearly polarized radiation along the 45– directions. The quadrifilar geometry combined with differential excitation significantly enhances both XPD and isolation performance. To further improve impedance matching, a branch structure is introduced to produce dual-resonant characteristics. Additionally, a defected ground structure (DGS) is employed to enhance the front-to-back ratio (FBR), without compromising the radiation performance in other directions. The theoretical mechanisms responsible for linear polarization, high XPD, and self-decoupling are rigorously analyzed and discussed. A prototype operating at the 3.55-GHz band is designed and fabricated to validate the proposed design. The antenna achieves a compact size with a diameter and height of only 0.28 λ0 and 0.25 λ0, respectively. The measured results show good agreement with simulations. Return coefficients at both ports remain below -10 dB across 3.12.3.82 GHz (20%), fully covering 5G NR band 78 (3300.3800 MHz). Within this band, the antenna achieves a measured boresight gain greater than 8.12 dBi, an XPD exceeding 26 dB, and a port isolation above 22 dB. The demonstrated performance of the DLP-QHA highlights its potential as an alternative solution for 5G-NR applications, including microcell base stations and Internet of Things (IoT) systems, particularly in scenarios requiring multi-polarization, multibeam, multiband, pattern-reconfigurable, and diversity array configurations.