Broadband circularly polarized NFRP antenna using crossed dipole driver

This paper presents a planar, broadband, electrically-small, circularly polarized (CP), near field resonant parasitic (NFRP) antenna fed by a crossed dipole driver. The driven and parasitic elements are printed on two separate thin substrates, which are stacked together with no air-gap to achieve the compact planar configuration. The technique of introducing meander lines and arrowhead-shaped endings in both elements is utilized to achieve the electrically small size. The parasitic and driven elements are designed to produce CP radiation at different frequency bands, which are then combined to obtain the broadband characteristic. The final design, whose driven and NFRP elements are implemented on two substrates of the same size, i.e., 35 mm × 35 mm × 0.508 mm, yields a measured S₁₁ < -10-dB bandwidth of 218 MHz (1.491-1.709 GHz) and 3-dB AR bandwidth of 145 MHz (1.490-1.635 GHz). Additionally, the antenna produces bi-directional radiation and has a high radiation efficiency.