Variable Reference Phase in Diffractive Antennas: Review, Applications, New Results
We review a free parameter in the design of Fresnel-zone-plate antennas. Historically, zone-plate antennas have been designed with a specific choice for this parameter. Two methods of interpreting the parameter have been identified, either in terms of a reference radius or, equivalently, a reference phase. For simplicity, here we treat this variable parameter as a reference phase. Importantly, the reference phase can be chosen to have non-standard values, which have been shown to improve important aspects of antenna performance and to add a new functionality to zone-plate antennas. In particular, a nearly linear one-to-one relationship between reference phase and the phase of the main-lobe beam exists, which is not present in the phase of sidelobes. This difference in phase response between main lobe and sidelobes is present independently of phase in feed circuitry: a zone-plate phase shift is fundamentally different from a feed phase shift. Frequency modulation of the reference phase thus appears as strong modulation of the main-lobe signal, but not of the signals through the sidelobes. This difference in frequency and phase response allows sidelobe signals to be discriminated against, making new applications possible. We review applications that exploit these features, including multipath-fading reduction, radar sidelobe-clutter reduction, and enhanced security in communications.
Available from: Germán Leon
- "These lenses keep on being of interest in antenna applications, both in Far Field (FF)4567 and in Near Field (NF) , due to their simplicity to manufacture and lower weight and profile when compared to classical dielectric lenses. "
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ABSTRACT: Fresnel Zone Plate Lenses (FZPLs) are transparent-opaque lenses that filter the desirable phase. The centred Fresnel lenses have a strong back radiation towards the feed. In order to solve this drawback, offset feeding or offset pointing lenses are used. In this work, both offset FZPLs are studied using an optical physics method and experimentally characterized in the millimeter band. Two prototypes have been manufactured and measured, presenting a narrow beamwidth. The characteristics of pointing of this beam are studied depending on the feed gain. This work shows the pointing characteristics of the lenses, simply moving the lens in a plane.
Available from: V.P. Yakubov
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ABSTRACT: The research of various parameters influence on the Fresnel reflector focusing properties in particular spatial sizes, the focal point position, etc. is conducted. The version of using a flat Fresnel reflector for receiving ultra-wideband signals with the use of Wiener filtering is suggested.
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