|Image of the 2x2 array of wire helix antennas.|
Sequentially rotating elements to form an array was originally investigated for increasing the main-beam axial ratio of patch antennas [Kraft]. Using this technique with an axial mode helix antenna, the gain and main-beam polarization is improved w.r.t a single element.
This axial-mode helix array consists of four identical helices placed in a 2-by-2 grid, rotated sequentially about their axis, and fed sequentially out of phase.
|Typical polarization specific gain pattern at the center frequency|
A comparison of the gain versus angle and the axial ratio versus frequency on broadside between a single axial-mode helix and a sequentially rotated array of axial-mode helices illustrates the performance improvement.
|Typical normalized circularly polarized gain versus angle pattern at the center frequency of a sequentially rotated array compared to a single element...|
|Typical axial ratio on boresight versus normalized frequency of a sequentially rotated array compared to a single element|
U. R. Kraft, "Main-beam polarization properties of four-element sequential-rotation arrays with arbitrary radiators", IEEE Transactions on Antennas and Propagation, vol. 44, no. 4, pp. 515-522, 1996.