Polarization-Insensitive Holographic Surfaces With Broadside Radiation

Scalar holographic surfaces (HSs) with a unique polarization-insensitive property are presented. The proposed HSs are constructed by sinusoidally modulated loop-wire unit cells, which can support both TE mode and TM mode propagation with the same phase velocity. The modulation principle in terms of refractive index is presented, which is convenient for HS designs concerning both TE and TM modes. A scalar polarization-sensitive HS using square patches exhibits a mismatch in the E- and H-plane beamwidths due to the sin (φ) circumferential illumination of the x-directed dipole, resulting in a low aperture efficiency. Two novel scalar HS designs using loop-wire configuration in square lattice and hexagonal lattice are proposed which exhibit the polarization-insensitive property with nearly circularly symmetric E- and H-plane beamwidths when illuminated by an x-directed dipole. Both simulations and measurements are carried out in this paper, which agree well with each other.