Design of a copper-tape-based impedance matching circuit for helical antennas using a Klopfenstein taper

Abstract

A practical copper-tape-based impedance matching circuit for helical antennas is presented, utilizing a Klopfenstein taper. The design uses standard acrylic cylinders and adhesive copper tape for low-cost fabrication without complex internal structures. The antenna achieves S₁₁ < -10 dB from 3.8 to 6.4 GHz, covering the 5.65-5.85 GHz range, with stable reflection coefficient characteristics. The insertion loss of the matching section was experimentally evaluated using a two-antenna method based on the Friis transmission equation, and was found to be less than 0.15 dB per matching section in the target operating band. This approach demonstrates a reproducible and low-loss matching technique suitable for microwave axial-mode helical antennas.