A high gain circularly polarised magnetoelectric dipole antenna array with metallic radiating structures for millimetre-wave applications

An antenna array design method of trade-off between high gain and low profile is proposed. A high-gain circularly polarised (CP) substrate integrated waveguide (SIW)-fed magnetoelectric dipole (ME-dipole) antenna array with metallic radiating structures is presented for millimetre-wave (MMW) applications. The CP antenna element comprises a set of horizontally and vertically metal plates and a metallic cavity that is excited by an X-shaped coupling slot etched on the broader side of SIW. The metallic cavity is designed to improve the gain and axial ratio (AR) performances. Utilising this antenna element, a proof-of-concept is established through the design of a 2 × 2 subarray and a 4 × 4 array. The fabricated 4 × 4 CP antenna array has a measured impedance bandwidth of 6.1% (36.4–38.7 GHz), with |S₁₁| ≤ −10dB. The measured 3dB AR bandwidth is 5.4% (36.0–38.0 GHz). The measured maximum gain achieved is 19.1 dBic. The height of the proposed array is 0.74λ₀ which is larger than the heights of typical SIW-based microstrip arrays (0.1–0.4λ₀) and lower than the heights of metallic arrays (larger than 2λ₀).