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 near-field 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
$\vert S_{11}\vert < -10$
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 \times $
(
$0.15\lambda b _{0})^{2} \times 0.0029\lambda b _{0} = 2.0\times 10^{-4} \lambda b _{0}^{3}$
, where
$\lambda b _{0}$
is the wavelength of the lower frequency bound, 1.35 GHz, giving ka =
$0.98.~\vphantom {^{\int }}$
Bidirectional electromagnetic fields are radiated with high radiation efficiency across the entire overlapping bandwidth.