Does somebody know what is structure of metamaterial unit cell used in Metawave's radar provided on the image below?
Is it metamaterial radiating element + varactor diode, or it is metamaterial phase shifting layer with some patch radiators underneath?
Found something similar (maybe) in article "Design of High-Gain and Beam Steering Antennas Using a New Planar Folded-Line Metamaterial Structure, Minh Thuy Le, Quoc Cuong Nguyen, and Tan Phu Vuong"
As you can see, there is actual patch antenna underneath, and some metamaterial layer on top.
Frequency is 5GHz, distance between patches and metamaterial surface is h=30mm, which is approximately half-wavelength at 5GHz. 30mm is huge, but Metawave's radar frequency is 76GHz to 81GHz. At 76GHz wavelength is around = 3.9mm. Then similar distance between metamaterial surface to patch array will be around 0.5*3.9= approx 2mm. This is tiny distance and actually both layers may be placed on a single multi-layer PCB (similar to image of Metawave's radar)
metamaterials are useful for slowwave structures. It is possible that they are using that property to make the antenna "look" like the antenna elements are spaced out further electrically, than they physically are.