Comparative Performance Evaluation of Multi-Turn Helical Antennas in Axial and Normal Modes for 5G and 6G Wireless Applications

Helical antennas can operate in axial and normal radiation modes, but their comparative performance across multiple turn counts and 5G/6G frequency bands remains insufficiently characterised. This study used full-wave electromagnetic simulation to compare both modes across low-, mid- and high-frequency bands. Helical antennas with two to eight turns were designed in Ansys HFSS Student Version 2025 R2 and evaluated at 3.5, 4.7, 28, 39, 110 and 300 GHz. The resulting 84 turn-frequency-mode cases were assessed using realised gain, axial ratio, return loss, voltage standing wave ratio (VSWR) and impedance bandwidth. In axial mode, the three-turn antenna produced the highest gain of 15.63 dB at 300 GHz. The two-turn antenna achieved the lowest axial ratio of 0.55 dB at 39 GHz and the widest bandwidth of 32.32 GHz at 300 GHz. In normal mode, the three-turn antenna provided the best impedance matching, with S11 of −57.89 dB and VSWR of 1.00 at 3.5 GHz. The findings show that the preferred turn count depends on the frequency band and performance objective. Normal-mode antennas with two to four turns are recommended for low-band 5G, axial-mode antennas with three to six turns for mid-band and millimetre-wave links, and axial-mode antennas with two to three turns for sub-terahertz systems. These results provide practical guidance for selecting helical antenna mode and turn count for 5G and emerging 6G applications.