A low-profile tri-band shared-aperture antenna for Sub-6G wide-beam and millimetre-wave high-gain applications

To achieve multi-function integration and independent performance regulation of microwave and millimetre-wave (mm-Wave) shared-aperture antennas, a design method based on embedded structure fusion is proposed. In the Sub-6G band, a high-order mode annular-ring patch antenna is designed. To transform the non-broadside characteristics, the current distribution of TM₃₁ and TM₁₂ modes is reconstructed by slotting in the centre of the patch. Additionally, the electric field distribution is modified by loading shorting pins to achieve beam broadening. In the 5G mm-Wave band, a four-element high-gain substrate integrated waveguide (SIW) slotted cavity backed antenna array with low-sidelobe characteristics is obtained using the element interleaving technique. The SIW slotted cavity backed antenna array is integrated into the central area of the annular-ring patch to achieve aperture-sharing fusion. Experimental results demonstrate that the antenna operates in the Sub-6G dual-band of 2.1–2.2 GHz and 5.2–5.4 GHz, respectively. Furthermore, the widest half-power beamwidth measured in these two bands is 126° and 140°. In the mm-Wave band, the operating bandwidth is 26.5–29.5 GHz, with a gain of up to 18.8 dBi. Notably, the performance of different bands does not impact the other, and the measured isolation exceeds 40 dB. Furthermore, the antenna profile is only 0.008 λ₀. Therefore, an ultra-low-profile microwave and mm-Wave shared-aperture antenna with multi-function integration and independent performance control is realised, which has great potential for application in 5G intelligent connected vehicle communications.