A single-layer dual-band shared-aperture antenna for vehicular communications is proposed in this article, which adopts a coplanar millimeter-wave (mm-Wave) band antenna embedded in a microwave band antenna. In the microwave Vehicle-to-Everything (V2X) band (5.905–5.925 GHz), an annular-ring patch antenna based on the TM ₁₂ mode is designed. A pair of slots are etched out on the radiating patch to reshape the current distribution of the TM ₁₂ mode, making it more codirectionally distributed. The sidelobe level can be completely suppressed from −5.2 dB, thus achieving better broadside radiation characteristics. In the 5G mm-Wave n257 band (26.5–29.5 GHz), a substrate integrated waveguide (SIW) slotted cavity backed antenna based on TE ₄₄₀ mode is designed, which achieves high gain and low sidelobe performance. Experimental results show that the impedance bandwidth of the microwave band is 3.7% (5.74–5.96 GHz), and that of the mm-Wave band is 10.9% (26.66–29.72 GHz). The mutual performances of the two antennas are hardly affected, and the measured isolation of both ports is greater than 45 dB. The measured gain reaches 10.8 dBi and 13.7 dBi, respectively, while maintaining sidelobe levels below −14.8 dB. At the same time, the antenna profile is only 0.015 λ ₀ ( λ ₀ is the wavelength in free space at low frequency). Therefore, a microwave and mm-Wave dual-band shared-aperture antenna with a compact structure and independently controllable performance is realized, which provides a promising candidate for different vehicular communication application scenarios.

Yangkun Zhu

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