Decoupling for Millimeter-Wave Array Antennas Using Near-Field Shrinking Dielectric Superstrate

Abstract

A decoupling concept of near-field shrinking dielectric superstrate (NFSDS) is proposed for large-scale, wideband, and dual-polarized mm-wave arrays. An NFSDS with a thickness of 4 mm ( $0.32 \lambda{0}$ at 24 GHz) is mounted seamlessly above the array, which shrinks the near field of the array elements to reduce the space wave coupling while slightly increasing the surface wave coupling of the arrays. By loading a superstrate with a certain thickness and low permittivity, the total coupling of the mm-wave arrays is reduced significantly. Periodic air holes are drilled through the superstrate to lower the NFSDS permittivity. An $8\times8$ mm-wave array is simulated, fabricated, and measured to verify the proposed decoupling concept. The simulated and measured coupling of the mm-wave array is reduced from -17 dB to lower than -23.2 dB from 24-29.5 GHz and lower than -25 dB in most of the band, respectively. The radiation patterns of the array before and after decoupling almost keep unchanged. Moreover, the NFSDS can efficiently improve the array beam scanning capability. The measured results align well with the simulated.