Loop-Based Circularly Polarized Grid Array Antenna With Edge Excitation

A loop-based grid array antenna (GAA) is proposed. The GAA is excited at one edge of the array and terminated to the ground plane at the other edge through a resistor. It is found that the proposed GAA, designated as the prototype GAA, has a frequency scanning function, with two circularly polarized (CP) frequency regions and a non-CP broadside-radiation frequency region. Subsequently, an advanced loop-based GAA is investigated to change the non-CP broadside radiation to CP radiation. For this, perturbation elements are added to the loops. It is revealed that the perturbation elements make the current flow along the loops in a traveling wave fashion. The advanced GAA has a seamless CP frequency scanning beam. The gain bandwidth is 23% (from 5.4 to 6.8 GHz), where the axial ratio is less than 3 dB, the radiation beam scans 51^° (from -22^° to +29^°), and the VSWR exhibits an acceptable value (less than 2.5) for practical applications.