Abstract-In practical applications, the low-profile spiral antennas suffer from the lack of proper planar feeding ways. The vertical balun always has a significantly long length, inconsistent with the requirements of the low profile spiral antenna geometry. A spiral antenna with integrated parallelplane feeding structure is proposed in this paper. The antenna used has obviously improved axial ratio compared to the equiangular spiral antenna at low frequencies. And the traditional balun in the third dimension is moved to the planar plane. The antenna and the Dyson-style balun have been integrated into a multi-layer structure. The resulting structure maintains the typical radiation behavior and the broadband operation of the spiral antennas, but the vertical balun is integrated at the same plane with the antenna. The overall size of the spiral antenna is largely reduced.

Abstract-A new spiral antenna is proposed in this paper. The developed antenna has improved axial ratio (AR) and shorted arm length. The formula of the new spiral is given. The developed spiral antenna combines the low frequency characteristic of power spiral antenna and high frequency characteristic of Archimedean spiral antenna. The growth rate of radial distance at large winding angle is close to power spiral for improved AR in low frequencies, and the growth rate at small winding angle is close to Archimedean spiral for good AR in high frequencies. The results reveal that the developed spiral antenna has noticeable improved axial ratio at low frequencies compared with Archimedean spiral antenna, and the problem of axial ratio degradation of power spiral antenna is also solved. The arm length is shorted by 46.4% compared to conventional Archimedean spiral antenna, and 63.5% compared to power spiral antenna.