A small quadrifilar helical antenna with parallel resonance circuit for dual-band application

Methods such as branching of the antenna element and meandering into a spiral are typically proposed for achieving dual-band quadrifilar helical antennas (QHAs). However, these methods suffer from drawbacks such as radiation pattern degradation of the antennas and a large number of design parameters. This paper proposes a dual-band QHA whose simple structure is realized by applying a parallel resonance circuit to the QHA. This antenna achieves dual-band resonance and is smaller than its conventional counterpart.