Showing papers on "Fresnel zone antenna published in 2012"

Design Equation for Multidielectric Fresnel Zone Plate Lens

Abstract: A structural design equation for multidielectric Fresnel zone plate (ZP) lens is outlined in this letter Based on this equation, multidielectric ZP lenses/lens antennas are studied numerically in the 30-50 GHz microwave band and contrasted to an ordinary plano-convex lens/lens antenna Usually, the ZP lens is made half-wavelength thick but we discovered that a similar wavelength thick lens can be built with lower-permittivity dielectrics, and that this lens can focus more efficiently In a confined frequency band, the thin and light-weight multidielectric ZP lens of four or more dielectric rings per full-wavelength zone is comparable in focusing to the ordinary bulky lens

CP metasurfaced antennas excited by LP sources

Abstract: A metasurface which is considered as a polarizer for microwave antennas is proposed in this paper. Preliminary results have shown that circularly polarized (CP) radiation can be obtained from linearly polarized (LP) source antennas with the use of metasurface, antenna performance such as realized gain, efficiency and bandwidth are improved simultaneously. The metasurfaced antennas have a succinct non-resonant cavity in sub-wavelength (1/13 λ 0 ) format.

Printed Hybrid Lens Antenna

Abstract: A novel printed hybrid lens antenna made of a 2-layer phase shifting surface (PSS) has been developed. It is a hybrid lens because the required operation is achieved by a combination of true phase correction (similar to a conventional lens, and previously reported PSS phase-correcting lenses) and amplitude-only correction (similar to a Fresnel zone plate). A prototype is fabricated and measured, revealing that the hybrid lens antenna has roughly twice the aperture efficiency of a Fresnel zone plate, and half that of a conventional lens. It provides an attractive compromise between performance, fabrication complexity and cost.

Analysis of focal-shift effect in planar metallic nanoslit lenses.

Abstract: A theoretical analysis based on scalar diffraction theory about the recently reported focal-shift phenomena in planar metallic nanoslit lenses is presented. Under Fresnel approximation, an axial intensity formula is obtained, which is used to analyze the focal performance in the far field zone of lens. The relative focal shift is totally dependent on the Fresnel number only. The influences of the lens size, preset focal length and incident wavelength can be attributed to the change of Fresnel number. The total phase difference of the lens is approximately equal to the Fresnel number multiplied by π. Numerical simulations performed using finite-difference time-domain (FDTD) and near-far field transformation method are in agreement with the theoretical analysis. Using the theoretical formula assisted by simple numerical method, we provide predictions on the focal shift for the previous literatures.

A Novel Printed Wideband Dipole Antenna

Abstract: We present a novel technique to improve the input bandwidth of a conventional printed dipole antenna without actually increasing its size. We show that the proposed modification results in a considerable improvement in the input bandwidth. We also propose an equivalent circuit model for this antenna and describe a procedure to determine the values of the circuit elements. Finally, the performance of the antenna is demonstrated by a fabricated model and a comparison of experimental results with simulation.

The grooved-dielectric Fresnel zone plate: An effective terahertz lens and antenna

Abstract: A number of microwave and terahertz grooved-dielectric Fresnel zone plate (FZP) and ordinary lenses and antennas are studed and compared numerically. Although the microwave (38 GHz) eight-step FZP lens is certainly inferior, the corresponding terahertz (1.5 THz) FZP lens is comparable in focusing action to the ordinary one. By use of a new design approach to the terahertz FZP lens/antenna the typical unwanted focusing shift from the design frequency is removed and even better focusing performance is obtained within a limited frequency band. Thus, at terahertz frequencies the dielectric FZP lens or antenna is a lightweight and an effective option to the ordinary lens or antenna. V C 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1343- 1348, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26812

On-chip THz 3D antennas

Abstract: In this work a new class of integrated 3D antennas is presented: the u-helix antenna class. U-helix is a truncated conical helix built using a novel MEMS (micro electro mechanical systems) technology directly realized on a silicon substrate, extruded from a planar spiral. The antenna is characterized by high gain (>6 dBi) and wide fractional bandwidth (0.4) in the 100 GHz to 1 THz frequency range. Fabrication processes of the antenna and simulated performances are reported, and its possible use in a THz rectifying device is presented.

New channel path loss model for near-ground antenna sensor networks

Abstract: The problem of very-near-ground path loss has been recently addressed via measurements in the literature. This study proposes a novel theoretical insight into the very-near-ground path loss problem. Here, the principles of Fresnel zone are used to develop an innovative theoretical model. It is depicted that part of the Fresnel zone is abstracted by the ground for very-near-ground antennas. This work shows that Fresnel zone abstraction creates an excess path loss when the heights of transmit and receive antennas are less than a `critical value`. The study theoretically derives this critical value in terms of the geometric mean of the transmitter and receiver heights. In addition, the study proposes a model for the path loss when antennas` heights meet this condition. Measurements are used to verify the proposed model.

Optoelectronic modulation of mm-wave beams using a photo-injected semiconductor substrate

Abstract: This thesis discusses optoelectronic devices at mm-wave frequencies, focusing on optoelectronic beamforming and non-mechanical beam steering based on an optically excited Fresnel zone plate plasma. The optically controlled zone plate, termed the photo-injected Fresnel zone plate antenna (piFZPA) within this work, is introduced and a comprehensive theoretical framework developed. The design and optimisation of Fresnel zone plates are detailed, which determine the inherent performance of the piFZPA. A range of zone plates were designed, fabricated, and characterised at 94 GHz with up to 46 dBi gain, -26 dB sidelobe levels, and 67% aperture efficiency being measured for a quarter-wave design. The control of (sub) mm-wave beams by optical modulation of the complex permittivity of a semiconductor substrate is discussed. The significance of the free-carrier plasma dynamics, the effective lifetime, surface recombination, and the limits of the substrate which are imposed by the spatial resolution of the free-carrier plasma are highlighted, with the optimisation of these parameters discussed. The passivation quality of high-resistivity silicon wafers were characterised using a mm-wave photoconductance decay method, which yielded lifetime improvements from τeff = 60μs up to τeff ≈ 4, 000 μs, resulting in lowered recombination velocities (S = 15 cm/s). W-band characterisations of the passivated wafers illustrate the significance of surface recombination, with measured attenuations of up to 24 dB.

First high dynamic range and high resolution images of the sky obtained with a diffractive Fresnel array telescope

Abstract: This paper presents high contrast images of sky sources, obtained from the ground with a novel optical concept: Fresnel arrays. We demonstrate the efficiency of a small 20 cm prototype Fresnel array for making images with high brightness ratios, achieving contrasts up to 4 × 105 on sky sources such as Mars and its satellites, and the Sirius A–B couple. These validation results are promising for future applications in space, for example the 4 m array we have proposed to ESA in the frame of the “Call for a Medium-size mission opportunity for a launch in 2022”. Fresnel imagers are the subject of a topical issue of Experimental Astronomy published in 2011, but only preliminary results were presented at the time. Making images of astronomical bodies requires an optical component to focus light. This component is usually a mirror or a lens, the quality of which is critical for sharp and high contrast images. However, reflection on a mirror and refraction through a lens are not the only ways to focus light: an alternative is provided by diffraction through binary masks (opaque foils with multiple precisely etched sub-apertures). Our Fresnel arrays are such diffractive focusers, they offer weight, price and size advantages over traditional optics in space-based astronomical instruments. This novel approach requires only void apertures of special shapes in an opaque material to form sharp images, thus avoiding the wavefront distortion, diffusion and spectral absorption associated with traditional optical media. In our setup, lenses and/or mirrors are involved only downstream (at small sizes) for focal instrumentation and chromatic correction. Fresnel arrays produce high contrast images, the resolution of which reaches the theoretical limit of diffraction. Unlike mirrors, they do not require high precision polishing or positioning, and can be used in a large domain of wavelengths from far IR to far UV, enabling the study of many science cases in astrophysics from exoplanet surfaces and atmospheres to galaxy evolution.

Linear Fresnel reflector (LFR) technology

Abstract: A single-axis linear Fresnel reflector (LFR) system is composed of many long row reflectors that together focus sunlight images that overlap on an elevated linear tower receiver running parallel to the reflector rotational tracking axis. This allows a large size array to be constructed inexpensively using very similar or identical long focal length (and therefore almost flat) glass mirror elements. The chapter reviews the historical and recent technical development of LFR technology. Thermal performance trade-offs and future trends are also examined.

Experimental Study on the Dependence of Antenna Type and Polarization on the Link Reliability in On-Body UWB Systems

Abstract: An experimental study on the use of ultra-wideband antenna systems (3.5–4.5 GHz) on the human body for wireless body area network (WBAN) applications is conducted. It has been found that the link reliability can be improved and transmit power can be reduced by properly selecting the transmit and receive antennas with different radiation properties (omni-directional, directional, pattern diversity) and polarizations (vertical and horizontal) at each location on the body. Moreover, when there is blockage by the body, it may be possible to achieve better transmission when the antennas are horizontally polarized. Also, antennas with pattern diversity can be used to enhance the overall reliability of the communication system. In order to eliminate the use of cables in the measurements, an on-body UWB system has been developed and the reliability can be assessed more practically in terms of the peak amplitude of the received waveform and the bit error rate. It has been observed that when the link quality is improved, the transmit power can be reduced by more than 20 dB without compromising on the reliability, which will conserve the battery power.

Computer simulation of Fresnel diffraction from double rectangular apertures in one and two dimensions using the iterative Fresnel integrals method

Abstract: We have applied the iterative Fresnel integrals method for the computation and simulation of the Fresnel diffraction images created by double apertures in one and two dimensions. Necessary formalism has been derived and the relevant computation algorithms have been developed for this application. The computer simulated images show an interesting combination of Fresnel diffraction images with mutual interference effects between the light diffracted from the two apertures. Transition to the expected Fraunhofer diffraction pattern for double apertures or slits is also observed by the simulations.

The efficiency of relief-phase diffractive elements at a small number of Fresnel zones

Abstract: A technique and investigation results are presented on the effect of the number of Fresnel zones on the diffraction efficiency and quality of the wave front formed by a diffractive optical element. Equations are presented for the microstructure reliefs of diffractive optical elements making (regardless of the number of Fresnel zones) the wavefront shape coinciding with the calculated one and ensuring 100% diffraction efficiency at a single wavelength and, in the case of two-layer structures, almost 100% diffraction efficiency in a wide spectral range.

Fresnel field to far field transformation using sparse field samples

Abstract: A method of antenna pattern reconstruction using sampling field data in sparse grid of points in Fresnel zone is presented. According to this method, antenna far field pattern in a desired section is reconstructed from several sections of the field in Fresnel region. Fresnel field to far field transformation is based on two-dimensional Fourier series expansion. Main features of the method are discussed. Computer simulation results are given.

Directional in-quadrature orthogonal-coil antenna and an array thereof for localization within a human body in a Fresnel region

Abstract: Body Area Networks (BANs) at a center frequency of 400MHz are not subject to the quasi-static limit, σ ≫ eω This makes it possible to capitalize on established theoretical results for small antennas Though the bulk of the body volume at 400MHz is still within the Fresnel region, major features of the classic far-field solutions may be readily applicable to BANs In this study, we introduce the concept of a small directional receiving/transmitting antenna comprised of two small orthogonal coils (magnetic dipoles) driven/acquired in quadrature to create a highly-directional single-lobe beam into the body An array of such radiators operating in the Fresnel region makes it possible to develop a simple yet effective localization algorithm within the body using RSS (Received Signal Strength) estimates for each individual element and superior to a receiving array of single-coil antennas

Dielectric Tube Antennas for Industrial Radar Level Gauging

Abstract: This paper concerns dielectric tube antenna design in the frequency range from 85 to 105 GHz for the use in the field of industrial radar level gauging for process automation industry The application is based on monostatic radar configurations, which thus demands for highly directive endfire antennas made of chemically inert dielectrics, such as polytetrafluoroethylene (PTFE) or polypropylene (PP) Herein, the antennas consist of solid and tubular waveguides with cylindrical cross sections as well as transitions among these sections In order to approach the promising theoretical directivity limits of thin-walled dielectric tubes at small aperture diameters, a fundamental HE11 mode-preserving waveguide transition forms the core element of the antenna This yields compact dielectric antennas with directivity levels of around 20 dBi By this means, a significant improvement in comparison to a circular metallic horn aperture of the same outer diameter as the radiating tube and a length reduction with regard to dielectric rod antennas is achieved Finally, prototypes of the proposed antennas are manufactured and verified by measurements

Dual-Band Dielectric Resonator Reflectarray for C/X-Bands

Abstract: A dual-band reflectarray antenna composed of notched rectangular dielectric resonators (NR-DR) of variable height is introduced in this letter. A single unit cell is designed to operate for C-band and X-band. All the elements are effectively used for dual-band operation. The proposed reflectarray provides wider bandwidth for both bands (C/X bands) when compared to conventional microstrip-based reflectarray antennas. Furthermore, the notch creates some space that can be used to incorporate active elements, RF/MEMS switches to achieve reconfigurable characteristics.

Monolithic integration of binary-phase Fresnel zone plate objectives on 2-axis scanning micromirrors for compact microscopes.

Abstract: We demonstrated a unique monolithic integration of Fresnel elliptical zone plate (EZP) objective on a 2-axis staggered vertical comb-drive micromirror with 500μm by 800μm surface area via direct patterning of reflective binary phase modulation elements on a silicon chip. The need for focusing optics is thus obviated, simplifying the micro-endoscope assembly and improving its form factor. The design of binary phase EZP was guided by simulations based on FFT based Rayleigh-Sommerfeld diffraction model. For dual-axis scanning angles up to 9o by 9o at the image plane, the simulated diffracted Airy disks on a spatial map have been demonstrated to vary from 10.5μm to 28.6μm. Micromirrors scanning ±9o (optical) about both axes are patterned with elliptical zones designed for 7mm focal length and 20þ off-axis 635-nm illumination using 635nm laser. Videos of samples acquired with ~15μm lateral resolution over 1mm × 0.35mm field of view (FOV) at 5.0 frames/second using the device in both transmission and reflectance modes bench-top single-fiber laser scanning confocal microscope confirmed the applicability of the device to micro-endoscopy.

Beam-steering antennas at millimeter wavelengths

Abstract: In many emerging applications of millimeter waves, electronic focusing and beam steering is needed. We present a survey of mm-wave beam steering antennas, where the necessary phase change for antenna elements is achieved using various electronically tuneable elements, e.g. microelectromechanical systems (MEMS), such as tuneable leaky-wave antennas, shaped lens antennas with integrated switched feed array, active reflectarray, tuneable high-impedance surface, and dielectric rod waveguides with integrated phase shifters. Some early results of our own relevant investigations are also presented.

The iterative Fresnel integrals method for Fresnel diffraction from tilted rectangular apertures: Theory and simulations

Abstract: We applied the iterative Fresnel integrals method for the numerical computation of Fresnel diffraction patterns from rectangular apertures tilted at an arbitrary angle to the optical axis. Detailed theoretical formalism is developed and discussed, and then is applied for the numerical computation and simulation of the actual diffraction patterns for an arbitrary optical configuration. The generated intensity distributions (images) show distortion and stretching in the direction of the tilt, but not in the other orthogonal direction. Significant decrease of the intensity is also predicted and observed, the decrease being proportionate with the tilt angle. The simulated images qualitatively resemble those published in the literature. In addition to single-axis tilts, simultaneous rotations (tilts) of the aperture in two orthogonal coordinate axes were also briefly considered and simulated.

Hybridization band gap based smart antennas: Deep subwavelength yet directional and strongly decoupled MIMO antennas

Abstract: In this paper, we show how the concept of hybridization band gaps can be utilized to create antennas for MIMO applications. Those strongly decoupled antennas present at the same time a very small form factor and a very low correlation. To that aim, we first explain briefly the concept of hybridization between a resonator and the free space waves continuum. Then we expose the methodology we use to design multi-ports antennas based on that concept. We present numerical and experimental results of 2 ports MIMO antennas at 2.45 GHz, printed on a PCB, whose areas are smaller than 2.6∗2.6 cm2. The two ports display experimentally peak gains of a about 4 dB, efficiencies of 80%, a coupling lower than −30 dB and a correlation lower than 0.1.

Recent achievements and future trends for multiple beam telecommunication antennas

Abstract: This paper describes a summary of THALES ALENIA SPACE France background in the field of space multibeam antennas for telecommunication applications. It starts with CIEL 2 Spacebus antenna subsystem operational in orbit since 2008. Then the main trends and antenna developments for Ka-band mission are addressed. A focus is made on KISS/ARTES3 EQM antenna that consists of a 2m full carbon reflector and very compact Tx/Rx dual polarization feeds. Finally recent achievements on YAHSAT 1B, ATHENA FIDUS and ARABSAT 5C are presented.

Fast numerical method for Focal Plane Array simulation of 3D Vivaldi antennas

Abstract: This paper presents the design and analysis of large Focal Plane Arrays (FPA) of thick Taper Slot Antennas (TSA). This communication extends the application of fast numerical method based on Macro Basis Functions (MBF) produced by Array Scanning Method (ASM) to the simulation of planar array of 3D Vivaldi antennas. This simulation technique is validated through the comparison with the brute force solution of a planar array containing 31 thick bowtie antennas. We also studied an array of 71 thick Vivaldi antennas in which we investigated the truncation effects at the array borders. Finally, the manufacturing feasibility of this type of thick Vivaldi antennas is verified by the development and measurement of an array of 4 thick metal only Taper Slot Antennas.

Active region and higher-order modes of spiral antennas

Abstract: The paper discusses characteristics of radiation, current distribution and excitation of the higher-order modes of the typical self-complementary spiral antennas. The investigated antennas are some of the leaky-wave antennas where the energy leaks during propagation through the spiral arms to produce radiated field. Radiation of the dominant first mode is formed in the specific area described as "the active region". This area depends on the rate of “wrap of the arms”. The investigated log-spiral and spiral Archimedean antennas have expansion of the arms exponential and linear, respectively. Expansion of the arms is only the function of angle and therefore these antennas belong to the class of frequency independent antennas.

Beam steering device

Abstract: An electrically variable lens comprising a variable Fresnel lens and a variable phase corrector plate. A liquid crystal variable Fresnel lens and liquid crystal phase corrector plate are varied in concert to compensate for wavefront discontinuities that would otherwise be produced by the Fresnel lens. The same principle is also used to provide a device capable of imposing an arbitrary spatial and temporal phase modulation on a wavefront.

High-gain beam-scanning reflectarray antennas using an active-feed scheme

Abstract: Beam scanning performance of active-feed reflectarray antennas are studied in this paper. The advantages of active-feed systems for high-gain beam scanning are delineated and bifocal reflectarray systems are investigated. It is shown that a conventional bifocal reflectarray cannot achieve a good performance over a wide angular range. The particle swarm optimization is then implemented to optimize the phase of the bifocal reflectarray system. A Ka-band reflectarray antenna designed for 60° beam scan and optimized for two beams at ±30° is demonstrated. Within the scanning range, the gain variation is smaller than 1.6 dB and the side lobe is lower than −15 dB.

Wideband unit-cell based on liquid crystals for reconfigurable reflectarray antennas in f-band

Abstract: A reconfigurable reflectarray-cell has been designed to provide a large tunable phase range in the frequency band 117–130 GHz. The unit-cell comprises three parallel dipoles printed on a quartz-wafer and a tunable liquid crystal (LC) placed on a cavity between the dipoles and a ground plane. The simulation results show a tunable phase-shift in a range larger than 300 degree for a 10% bandwidth and low sensitivity to the angle of incidence.