Axial ratio characteristics of an Archimedean spiral antenna on a thin magnetic material

This paper describes the axial ratio characteristics of an Archimedean spiral antenna placed on a thin magnetic material. The thin magnetic material having a high permittivity and some magnetic loss tangent is used. The outer circumference of the spiral antenna is chosen to be approximately one wavelength at 300 MHz. To obtain a unidirectional beam, the antenna is located above a ground plane. The proposed antenna is analyzed using the finite-difference time-domain method. For comparison, a spiral antenna without the thin magnetic material is also analyzed. We have come to the conclusion that the spiral antenna on the thin magnetic material radiates a circularly polarized wave at lower frequencies.