Abstract
This paper examines the binary Fresnel zone plate (FZP) lens frequency-harmonic and space-resolution focusing, and its application as a FZP lens antenna. A microwave FZP lens antenna (FZPA) radiates both at design (90 GHz) and terahertz (THz) odd harmonic frequencies. Frequency and space domain antenna operation are studied analytically by use of the vector diffraction integral applied to a realistic printed FZPA. It is found that all harmonic gain peaks are roughly identical in form, bandwidth, and top values. At each harmonic frequency, the FZPA has a beamwidth that closely follows the Rayleigh resolution criterion. If the lens/antenna resolution is of prime importance and the small aperture efficiency is a secondary problem the microwave-design FZP lens antenna can be of great use at much higher terahertz frequencies. Important feature of the microwave FZP lens is its broader-zone construction compared to the equal in resolution terahertz-design FZP lens. Thus, unique and expensive microtechnology for the microwave FZP lens fabrication is not required. High-order harmonic operation of the FZP lens or lens antenna could find space resolution and frequency filtering applications in the terahertz and optical metrology, imaging tomography, short-range communications, spectral analysis, synchrotron facilities, and so on.
Highlights
During the last two decades, a rapid exploration of terahertz waves is taking place [1,2,3]
It is fascinating that the big microwave-design antenna FZP lens antenna (FZPA)-M-10 could operate at frequency harmonics much higher than the terahertz frequencies or in the infrared band, for instance, for which the antenna aperture efficiency will be really extremely low
The study exposes for the first time a number of intriguing features related to the binary microwave Fresnel zone plate (FZP) lens and antenna operating at harmonic terahertz frequencies
Summary
During the last two decades, a rapid exploration of terahertz waves is taking place [1,2,3]. If the high lens resolution and small thickness are of prime importance, the binary FZP lens consisting of freestanding or printed skinny metal rings would be preferable. Such lenses have found a lot of applications in the areas of 3D imaging tomography, electron microscopy, sensing and security systems, and synchrotron radiation facilities for beam focusing [11, 14,15,16,17,18,19]. The paper is completed by a general conclusion, acknowledgement, and list of references
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