The phase-correcting zone-plate

TLDR: In this article, the use of the zone plate as a focusing or a frequency-filter device at millimeter wavelengths is described, and sample design data are given, as well as references to prior results.

Abstract: A description is given of the use of the zone plate as a focusing or a frequency-filter device at millimeter wavelengths. Sample design data are given, as well as references to prior results. A newer type of zone plate is discussed which employs two dielectrics of equal thickness to produce a flat or planar zone plate.