ON THE SUBZONE PHASE CORRECTION OF FRESNEL ZONE-PLATE ANTENNAS

Subzone phase correction is a practical technique to produce high-effi ciency Fresnel zone plate antennas. In this article a strict theory un derlying the technique is presented. A closed-form expression of the f ocal field for the subzone phase correcting Fresnel zone plate (FZP) i lluminated by a plane wave is given first. The subzone division and th e corresponding phase correction are then optimized to produce the max imum focal field intensity. To overcome the difficulty of placing many subzone phase shifters in the narrow outer full-wave zones, an aperio dic subzone phase correction technique is proposed. (C) 1993 John Wile y & Sons, Inc.