Application of a Parasitic Loop on Loosely Wound Short-Arm Spiral Antennas

Yasuhiro KAZAMA
Nagayoshi MORITA

IEICE TRANSACTIONS on Communications   Vol.E81-B       pp.2205-2211
Publication Date: 1998/11/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Category: Antennas and Propagation
loosely wound short-arm two-wire archimedean spiral antenna,  axial ratio,  power gain,  current distribution,  

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Loosely wound short-arm two-wire Archimedean spiral antennas are investigated. It is shown that good circularly polarized waves with axial ratio less than 2 dB are obtained when the outer circumference C of the spiral antenna is in the range of about 1. 3λ < C < 1. 5λ, where λ is the free-space wavelength. To improve the antenna characteristics further, spiral antennas combined with a parasitic loop are examined. It is clarified that the parasitic loop greatly contributes to the improvement of the axial ratio and power gain.