Dual-Band Shared Aperture Reflectarray and Patch Antenna Array for S- and Ka-Bands

In this communication, a dual-band shared aperture antenna is presented. The proposed antenna achieves dual-band operation by housing both a low-frequency patch antenna array and a high-frequency reflectarray in the same aperture area. The two different antenna types are combined into a single-antenna product without any significant performance loss. The antenna has a layered structure that allows the low-frequency antenna array to have both a sufficient impedance bandwidth and realized gain. The antenna has a shared aperture since the high-frequency reflectarray has unit elements within the area of the low-frequency patch antenna array. This allows the antenna to achieve a good realized gain in the high-frequency band. The proposed antenna is fabricated and measured. The prototype is designed for S- and Ka-bands resulting in a frequency ratio of 7.37. The shared aperture size is 156 mm <tex-math notation="LaTeX">×156 </tex-math> mm <tex-math notation="LaTeX">×4.624 </tex-math> mm ( <tex-math notation="LaTeX">1.82λ × 1.82λ × 0.05λ </tex-math> at S-band and <tex-math notation="LaTeX">13.4λ × 13.4λ × 0.40λ </tex-math> at Ka-band). Measurements show the impedance bandwidth to be 200 MHz (6%) and 5.1 GHz (20%) and the peak realized gain to be 13.70 and 27.65 dBi at 3.5 and 25.8 GHz, respectively. A very good agreement between the simulated and measured results is observed.