Electrically Small, Wideband, Circularly Polarized, Inductive Grid-Array Metasurface Antenna

A wideband, circularly polarized (CP), electrically small antenna (ESA) with two axial ratio (AR) poles is reported. The design is composed of a specially engineered L-shaped driven dipole, a nearfield resonant parasitic (NFRP) crossed Egyptian axe dipole (EAD), and an NFRP inductive grid-array metasurface. The L-shaped driven dipole simultaneously excites two degenerate modes of the crossed-EAD with an intrinsic 90. phase shift to produce one AR pole. Similarly, it also effectively excites two orthogonal modes of the grid-array metasurface to generate the second AR pole. A wide AR bandwidth is achieved by pressing these two AR poles close together. The measured results agree well with their simulated ones. The measured impedance bandwidth, where vertical bar S-11 vertical bar < -10 dB, ranges from 1.28 to 1.73 GHz (29.9%) and the 3-dB AR bandwidth ranges from 1.35 to 1.66 GHz (20.5%). Consequently, a broad 20.5% overlapping bandwidth, from 1.35 to 1.66 GHz, is obtained. The total dimensions of this ESA are pi x (0.15 lambda(0))(2) x 0029 lambda(0) = 2.0 x 10(-4) lambda(3)(0) where lambda(0) is the wavelength of the lower frequency bound, 1.35 GHz, giving ka = 0.98. Bidirectional electromagnetic fields are radiated with high radiation efficiency across the entire overlapping bandwidth.