The 2D Linearly Polarized Near-Field Focusing Based on Angularly   Discretized Slot Arrays
  A 2-D near-field focusing design is proposed based on the circular slot array waveguide structures, synthesized using the array-factor theory, and demonstrated by full-wave simulations. The principle of beam-focusing is extended to the 2-D angularly discretized configuration using regular center-fed linear slots arranged in a circular pattern. By the mirror image arrangement of the slots, a linearly polarized focus in the near-field of the antenna, with negligible cross-polarization is achieved. Its beam-focusing properties are discussed in details and demonstrated by simulations. 
Menglin Chen, Shulabh Gupta, Zilong Ma and Lijun Jiang
physics.optics