A Dual-Band Shared-Aperture Antenna for Microwave and Millimeter-Wave Applications in 5G Wireless Communication

The shared-aperture integration of microwave (MW) and millimeter-wave (MMW) band antennas has attracted lots of attention and interests recently. However, few designs, to date, can simultaneously satisfy the requirements of compact size for MW antenna, beam steerable array for MMW antenna, appreciable bandwidths for both bands, and high isolation between the two bands. In this communication, a dual-band 3.5/28 GHz shared-aperture antenna is proposed to solve this issue. By embedding two MMW <inline-formula> <tex-math notation="LaTeX">$1\times $ </tex-math></inline-formula> 2 subarrays to the MW perforated patch antenna, the two antenna types can be accommodated in a shared volume and integrated into the same structure. The shared-aperture antenna, which has a very compact size of <inline-formula> <tex-math notation="LaTeX">$0.4\times 0.26\times 0.04\,\,\lambda ^{3}_{01}$ </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">$\lambda _{01}$ </tex-math></inline-formula> is the wavelength in the vacuum at 3.5 GHz), can be used as an array element to form the MW MIMO system and MMW beam-steering array. A validation array model with two cells is fabricated and measured. Measured results show that the antenna can cover a dual band of 3.38–3.64 GHz (7.4%) and 26.4–29.8 GHz (12.1%). The peak gains of 6.9 and 14.6 dBi are obtained by the single MW element and <inline-formula> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> 2 MMW array, respectively. The MMW array can support ±30° beam scanning in the H-plane. The channel isolation between the two bands can be more than 45 dB at 3.5 GHz and 40 dB at 28 GHz.