The focal properties of microwave lenses with F-numbers of the order of unity have been experimentally investigated. The intensity and phase distributions in the focal region have been studied for several systems of polystyrene lenses utilizing microwave frequencies between 9.2 GHz and 70 GHz. The results have been compared with theoretical predictions based on scalar diffraction theory. An assessment of the useful values of beam width and depth of field is given.
A. I. Carswell and C. Richard, "Focal Properties of Microwave Lenses with Small F-Numbers," Appl. Opt. 10, 346-357 (1971)