Recent Advances in Fresnel Zone Plate Antenna Technology

This paper outlines some of the recent advances in Fresnel zone plate antenna technology. Sidelobe reduction and control over sidelobe location are two developments, which are useful for interference reduction. Another development is the focusing resolution of Fresnel zone plate antennas for sub-wavelength focal distances. Designs will be given for spatial resolutions of less than λ/2.

Introduction

The aperture of the conventional Fresnel zone plate antenna (FZPA) is planar and consists of circular zones which alternate between air and metal as shown in Fig. 1. The FZPA is illuminated by a feed antenna located along the zaxis at a distance F from the aperture plane and the overall diameter of the antenna is D. The metal zones represent the locations on the surface of the aperture where the electromagnetic waves from the source are 180o out of phase relative to the center of the aperture.

The Page 1 of 15 metal zones block the out of phase waves while the waves passing through the air zones combine constructively to collimate a beam in the far field. The waves that are blocked by the metal zones therefore do not contribute to the antenna radiation pattern.

Due to overcrowding problems in the lower frequency bands and to the ever-increasing demand for more bandwidth, the Ka-band (26 GHz – 40 GHz) has been drawing significant attention over the last few years for future wireless applications.