Phase-correcting Fresnel Zone Plate Research Articles

Using Rotatable Planar Phase Shifting Surfaces to Steer a High-Gain Beam

Phase shifting surface (PSS) technology has been used to develop a 30 GHz beam steering antenna. The concept is similar to that of a pair of dielectric wedges placed in front of a primary antenna for beam steering. The initial prototype antenna is made of a horn-fed PSS phase-correcting Fresnel zone plate above which are placed two rotatable circular linear phase progression PSSs. These PSSs have rotation capability along their planes. Their rotation allows for achieving beam steering in the upper hemisphere. An additional prototype antenna makes use of a rotatable offset-beam PSS phase-correcting Fresnel zone plate and a single linear phase progression PSS to achieve beam steering with a higher aperture efficiency. These prototypes confirm the feasibility of using PSS technology for achieving a lightweight, low-cost and efficient beam steering antenna.

Thin microwave phase-shifting surface lens antenna made of square elements

A 90° phase-correcting Fresnel zone plate (FZP) antenna has been realised at 30°GHz using a thin three-layer microwave phase-shifting surface (PSS) with square conducting shapes as the unit cell elements. These square elements allow dual-polarisation or circular-polarisation capabilities, which could not be achieved by the previously reported PSS structures the unit cell elements of which were strip-based. This new PSS lens was compared with the previously reported strip-element version. The square element PSS lens has slightly higher gain, but a small degradation to cross-polarisation level and gain bandwidth. The effect of altering the roll angle of the lens with the feed kept fixed was also investigated. This revealed that gain bandwidth is unchanged, but there is a marginal gain degradation and increase in the cross-polarisation level (albeit still well within an acceptable range) for certain roll angles.

Design of mm-wave phase-correcting fresnel zone plate reflector antenna with continuous structure

Based on scalar diffraction optics theory, a new type of mm-wave antenna(diffraction antenna) phase-correcting Fresnel zone plate with continuous structure is described in this paper. It has the advantages of thinner thickness, lighter weight and design flexibility. The design theory and space shadow are discussed in details, and the measured results are presented. The results show that the properties of this kind of antenna is closed to paraboloid reflector.

Multilayer offset Fresnel zone plate reflector

An offset phase-correcting Fresnel zone plate (FZP) reflector antenna based on the multilayer configuration is presented. The reflector consists of a conducting ground and four layers of conducting patterns separated by four dielectric substrates. An experimental prototype designed at 10.39 GHz was fabricated and tested. With a 0.32 m by 0.34 m elliptical reflector aperture and a pyramidal feedhorn, the antenna achieved -20-dB sidelobe level and 61% maximum efficiency. Compared with a phase reversal FZP of the same size, a 3.3-dB gain improvement and significant sidelobe reduction were obtained. >

Millimeter-Wave Characteristics of Phase-Correcting Fresnel Zone Plates

A focusing element called the phase-correcting Fresnel zone plate is described, and its characteristics are given when used in the millimeter-wave region for imaging or frequency filtering in place of a lens. Two versions are discussed, one where alternate concentric annular grooves are cut in a single piece of low-loss dielectric, and a second where two (or more) dielectrics are used in alternate concentric rings. For the latter case, an appropriate choice of parameters produces a design of constant thickness (i.e., a flat disk), named the "planar lens." Design formulas and curves, as well as measured results, are given for both types, and an analytical description is derived for the far-field patterns. Compared with lenses, zone plates are simpler to construct and have lower absorption loss, thickness, and weight.