Circularly Polarized Spiral-Grid Array Antenna for Beam Scanning

The long side lines for the Kraus-type C-GAA are modified to meandering lines in [3]. It is found that the meandering lines contribute to controlling the HPBW in the H-plane, keeping the HPBW in the E-plane constant. In [4], the long side lines are replaced with bent lines, and it is revealed that, as the bend angle is increased, the HPBWs in the two principal planes become wider. The short side lines for the Kraus-type C-GAA have also been modified in [5], where the strip conductors are used. By selecting the conductor width, this C-GAA shows a wide frequency response of the VSWR. Note that this C-GAA radiates a linearly polarized wave. An array antenna that radiates a circularly polarized (CP) wave is found in [6], where cfigured elements are placed above the Kraus-type C-GAA. The maximum radiation from this array is in the direction normal to the grid array plane. A CP C-GAA in [7] has loops for the grid short sides, each having perturbation elements. The maximum radiation from this CP array is in the direction normal to the grid array plane, as in [6]. This paper presents a novel E-GAA that radiates a CP beam, whose direction varies with frequency. This CP E-GAA uses spiral elements for the grid short sides. The radiation characteristics, including the beam direction, axial ratio, and radiation pattern, are analyzed and discussed.