Two-arm eccentric spiral antenna
- 1 April 1997
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Transactions on Antennas and Propagation
- Vol. 45 (4) , 723-730
- https://doi.org/10.1109/8.564099
Abstract
This paper presents a free-space analysis of a planar two-arm eccentric spiral antenna. The eccentricity generates a circularly polarized wave with the main beam directed off-normal to the spiral plane. Input impedance and radiation characteristics are calculated from the current distribution generated by a method of moments solution. The radiation characteristics include power gain and axial ratio patterns. Three-dimensional (3-D) gain surface plots illustrate off-normal dependence of the eccentricity constant. The eccentric spiral antenna is found to have a significant increase in gain. This occurs when adjacent spiral arms rotating 360/spl deg/ have an electrical length increase of one wavelength. Thus, adjacent currents on one side of the spiral are nearly all in-phase. On the opposite side of the spiral, all neighboring currents are nearly out-of-phase. Evaluation of these currents result in a theory of operation for eccentric spiral antennas.Keywords
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