A Low-Profile Shared-Aperture Patch Antenna With 2-D Scanning Capability

This letter presents a novel low-profile patch antenna with shared aperture and two-dimensional scanning capability. Compared with the state-of-the-art designs, the proposed antenna offers low cost and easy integration due to its simple structure. The millimeter-wave (MMW) stacked patch antenna array is embedded in the weak electric-field (E-field) region of the antiphase TM₂₀ mode and TM₁₂ mode of the microwave (MW) dual-patch antenna. This design interleaves two antenna types within the same aperture, achieving natural isolation. Slots on the MW patch modify the current path of the antiphase TM₂₀ mode and the TM₁₂ mode, enabling dual-mode operation with low profile. The stacked patches provide wideband operation in MMW frequency band. Additionally, periodic slots on the MW patch facilitate MMW beam scanning, achieving ±45° beam scanning at both E- and H-planes. For demonstration, a prototype of the proposed MW and MMW shared-aperture patch antenna is fabricated and measured, which has a total size of 0.38λ_L × 0.48λ_L × 0.022λ_L (λ_L is the operating wavelength at 4.6 GHz in free space). Measurements show a 10 dB impedance matching bandwidth of 6.6% and 27.1% and a peak gain of 7.2 dBi and 15.5 dBi in MW and MMW bands, respectively.