Far-field pattern determination from the near-field amplitude on two surfaces

1990 ◽  
Vol 38 (11) ◽  
pp. 1772-1779 ◽  
Author(s):  
O.M. Bucci ◽  
G. D'Elia ◽  
G. Leone ◽  
R. Pierri
Keyword(s):  
Near Field ◽  
Field Amplitude ◽  
Field Pattern ◽  
Far Field ◽  
Pattern Determination ◽  
Far Field Pattern

scholarly journals Scattering centers modeling of non-anechoic measurement environments

2012 ◽  
Vol 10 ◽  
pp. 69-73 ◽  
Author(s):  
K. A. Yinusa ◽  
C. H. Schmidt ◽  
T. F. Eibert
Keyword(s):  
Near Field ◽  
Field Measurements ◽  
Field Pattern ◽  
Far Field ◽  
Scattering Centers ◽  
Field Transformation ◽  
Field Radiation ◽  
Echo Suppression ◽  
Multipath Signals ◽  
Far Field Pattern

Abstract. Near-field measurements are established techniques to obtain the far-field radiation pattern of an Antenna Under Test via near-field measurements and subsequent near-field far-field transformation. For measurements acquired in echoic environments, additional post-processing is required to eliminate the effects of multipath signals in the resulting far-field pattern. One of such methods models the measurement environment as a multiple source scenario whereby the collected near-field data is attributed to the AUT and some scattering centers in the vicinity of the AUT. In this way, the contributions of the AUT at the probe can be separated from those of the disturbers during the near-field far-field transformation if the disturber locations are known. In this paper, we present ways of modeling the scattering centers on equivalent surfaces such that echo suppression is possible with only partial or no information about the geometry of the scatterers.

scholarly journals Progress towards the realization of an optical Far-Field Superlens

2021 ◽  
Author(s):  
◽  
Farzaneh Fadakar Masouleh
Keyword(s):  
Zinc Oxide ◽  
Near Field ◽  
Diffraction Gratings ◽  
Evanescent Waves ◽  
Field Pattern ◽  
Far Field ◽  
Potential Candidate ◽  
Plasmonic Material ◽  
Far Field Pattern ◽  
The Impact

<p>Conventional optics suffer from a fundamental resolution limit due to the nature of light. The near-field superlens concept was introduced two decades ago, and its theory for enabling high resolution imaging is well-established now. Initially, this superlens, which has a simple setup, became a hot topic given the proposition of overcoming the diffraction limit. It has been demonstrated that a near-field superlens can reconstruct images using evanescent waves emanating from small objects by means of resonant excitations on the surface of the superlens. A modified version of the superlens named the far-field superlens is theorized to be able to project the near-field subwavelength information to the far-field region. By design, the far-field superlens is a near-field superlens with nanostructures added on top of it. These nanostructures, referred to as diffraction gratings help couple object information available in the evanescent waves to the far-field. Work reported in this thesis is divided to two major sections. The first describes the modelling technique that investigates the performance of a far-field superlens. This section focuses on evaluating the impact of the diffraction gratings geometry and the object size on the far-field superlens performance as well as the resulting far-field pattern. It was shown that a far-field superlens with a nanograting having a duty cycle of 40% to 50% produces the maximum intensity and contrast in the far-field interactions. For periodic rectangular objects, an inverse-trapezoidal nanograting was shown to provide the best contrast and intensity for far-field interactions. The minimal simulation domain to model a symmetric far-field superlens design was determined both in 2D and 3D. This input reduced the required modelling time and resources. Finally, a 3D far-field superlens model was proposed, and the effect of light polarization on the far-field pattern was studied. The second section of this thesis contains the experimental study that explores a new material as a potential candidate for the construction of far-field superlens. The material conventionally used for superlens design is silver, as its plasmonic properties are well-established. However, scaling down silver features to the nanoscale introduces fundamental fabrication challenges. Furthermore, silver oxidizes due to its reactions with sulphur compounds at ambient conditions, which means that operating a silver far-field superlens is only possible in a well-controlled environment. This disagrees with our proposed concept of a low-cost and robust superlens imaging device. On the other hand, highly doped semiconductors are emerging candidates for plasmonic applications due to the possibility of tuning their optical and electrical properties during the fabrication process. While the working principle of a superlens is independent of the plasmonic material of choice, every plasmonic material has a particular range of operating wavelengths. The pros and cons of each plasmonic material are usually identified once used experimentally. In this work, aluminium-doped zinc oxide was the proposed material of choice for the far-field superlens design. The second part of this thesis details the characterization results of the optical, electrical and structural properties of this proposed alternative. Our aluminium-doped zinc oxide samples were highly transparent for large parts of the spectrum. Their carrier concentration was of the order of 10+20 cm-3, and a resistivity of about 10-3 Ω.cm was achieved. The modelled dielectric permittivity for the studied samples showed a cross-over frequency in the near-infrared region, with the highest plasma frequency achieved in this study being 4710 cm-1.</p>

Determination of Far-Field Pattern of Rigid Scatterers Using Independent Finite Element Method and Eigenfunction Expansion, Part 1: Axisymmetric Scattering

1996 ◽  
Vol 118 (4) ◽  
pp. 575-582 ◽  
Author(s):  
C. P. Vendhan ◽  
C. Prabavathi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Eigenfunction Expansion ◽  
Near Field ◽  
Prolate Spheroid ◽  
Field Pattern ◽  
Far Field ◽  
Outer Domain ◽  
Far Field Pattern ◽  
Element Method

The near-field steady state scattered potential around a rigid scatterer subjected to plane incident wave is computed using the finite element method with radiation boundary dampers on a finite truncation boundary. Then the solution in the outer domain is sought in the form of an eigenfunction expansion and the expansion coefficients are obtained using the finite element solution on the truncation boundary as Dirichlet boundary condition. The scattered far-field pattern is derived from this solution for prolate spheroid and hemispherically capped cylinder problems.

Far-field pattern reconstruction directly from a minimum number of helicoidal near-field data

2012 ◽  
Author(s):  
Francesco D'Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Field Data ◽  
Near Field ◽  
Field Pattern ◽  
Far Field ◽  
Minimum Number ◽  
Pattern Reconstruction ◽  
Far Field Pattern

scholarly journals Short-Range Wireless Transmission in the 300 GHz Band Using Low-Profile Wavelength-Scaled Dielectric Cuboid Antennas

2021 ◽  
Vol 2 ◽  
Author(s):  
Kazuki Yamada ◽  
Yuto Samura ◽  
Oleg V. Minin ◽  
Atsushi Kanno ◽  
Norihiko Sekine ◽  
...  
Keyword(s):  
Short Range ◽  
Transmission Rate ◽  
Near Field ◽  
Error Rates ◽  
Wireless Transmission ◽  
Field Pattern ◽  
Far Field ◽  
Low Profile ◽  
Antenna Type ◽  
Far Field Pattern

A short-range terahertz (THz) wireless transmission in the 300 GHz band is demonstrated using low-profile wavelength-scaled dielectric transmitting and receiving cuboid antennas (DCAs). These dielectric cuboid antennas are made of polytetrafluoroethylene with dimensions of approximately 1.2 mm × 1.2 mm × 1.3 mm. The near-field pattern of a DCA at 300 GHz was measured using an electro-optic sensing technique, and its far-field pattern characterization was based on the near-field to far-field transformation. The measured antenna gain was 15.06 ± 0.06 dBi. By employing DCAs as transmitting and receiving antennas, a 17.5 Gbps data transmission rate at distances of approximately 200 and 50 mm with bit error rates of 3.31 × 10–3 and 7.51 × 10–7 respectively, is demonstrated. The proposed mesoscopic scale DCA is a promising antenna type in intra-device communications and Kiosk download applications for future mobile devices operating in the 300 GHz band.

Experimental Testing on an Effective Technique to Reconstruct the Far- Field Pattern of a Long Antenna from Near-Field Measurements Acquired via Spherical Spiral Scan

2014 ◽  
Vol 8 (1) ◽  
pp. 1-9 ◽  
Author(s):  
F. D’Agostino ◽  
F. Ferrara ◽  
C. Gennarelli ◽  
R. Guerriero ◽  
M. Migliozzi
Keyword(s):  
Experimental Testing ◽  
Near Field ◽  
Field Measurements ◽  
Field Pattern ◽  
Far Field ◽  
Positioning Systems ◽  
Spiral Scanning ◽  
The University ◽  
Far Field Pattern ◽  
Spiral Scan

In this paper, the experimental validation of a fast and accurate near-field – far-field (NF–FF) transformation with spherical spiral scanning for elongated antennas is provided. Such a transformation relies on a nonredundant sampling representation of the voltage measured by the probe, obtained by using the unified theory of spiral scans for nonspherical antennas and adopting a cylinder ended in two half-spheres to model long antennas. It allows a remarkable reduction of the measurement time due to the use of continuous and synchronized movements of the positioning systems and to the reduced number of needed NF measurements. In fact, the NF data required by the classical spherical NF–FF transformation are efficiently and accurately recovered from those collected along the spiral, by using an optimal sampling interpolation expansion. Experimental results, obtained at the Antenna Characterization Lab of the University of Salerno and assessing the effectiveness of such a NF–FF transformation, are shown.

Near-field to far-field pattern measurements for a low-frequency FR-ORA

2015 ◽  
Author(s):  
Eman O. Farhat ◽  
Kristian Z. Adami ◽  
Anthony K. Brown ◽  
Yongwei Zhang ◽  
Charles V. Sammut
Keyword(s):  
Near Field ◽  
Low Frequency ◽  
Field Pattern ◽  
Far Field ◽  
Far Field Pattern
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