A Modified Grid Array Antenna Radiating a Circularly Polarized Wave

This paper presents a modified grid array antenna whose radiation elements are loops, which are designed to radiate a circularly polarized wave. The array antenna has a low profile, that is, the distance from the loops to the ground plane, H, is extremely small: H = 3.5 mm (= 0.08 wavelength at 7 GHz). Analysis reveals that a modified grid array composed of nine loops has a 2.3% frequency bandwidth for a 3-dB axial ratio criterion, with a maximum gain of approximately 15 dBi.