scholarly journals Reconfigurable Antenna Arrays with Multiple Requirements: A Versatile 3D Approach

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Massimiliano Comisso ◽  
Giulia Buttazzoni ◽  
Roberto Vescovo
Keyword(s):  
Antenna Arrays ◽  
Mutual Coupling ◽  
Dynamic Range ◽  
Near Field ◽  
Field Pattern ◽  
Deterministic Method ◽  
Iterative Minimization ◽  
Array Structures ◽  
Far Field Pattern ◽  
Ratio Reduction

This paper proposes a deterministic method for the 3D synthesis of antenna arrays that jointly accounts for far-field pattern reconfigurability, polarization setting, dynamic range ratio reduction, and near-field control. The conceived algorithm, which generalizes some existing solutions, relies on a weighted cost function, whose iterative minimization is accomplished by properly derived closed-form expressions. This feature, combined with the possibility of selecting the weighting parameters, provides a fast and versatile approach, whose capabilities are numerically checked by considering different synthesis problems and array structures in the presence of mutual coupling.

scholarly journals High-isolation antenna array using SIW and realized with a graphene layer for sub-terahertz wireless applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Alibakhshikenari ◽  
Bal S. Virdee ◽  
Shahram Salekzamankhani ◽  
Sonia Aïssa ◽  
Chan H. See ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Antenna Arrays ◽  
Integrated Circuit ◽  
Mutual Coupling ◽  
Near Field ◽  
Dielectric Substrate ◽  
Patch Antennas ◽  
Reference Array ◽  
Radiation Properties ◽  
Array Structures

AbstractThis paper presents the results of a study on developing an effective technique to increase the performance characteristics of antenna arrays for sub-THz integrated circuit applications. This is essential to compensate the limited power available from sub-THz sources. Although conventional array structures can provide a solution to enhance the radiation-gain performance however in the case of small-sized array structures the radiation properties can be adversely affected by mutual coupling that exists between the radiating elements. It is demonstrated here the effectiveness of using SIW technology to suppress surface wave propagations and near field mutual coupling effects. Prototype of 2 × 3 antenna arrays were designed and constructed on a polyimide dielectric substrate with thickness of 125 μm for operation across 0.19–0.20 THz. The dimensions of the array were 20 × 13.5 × 0.125 mm3. Metallization of the antenna was coated with 500 nm layer of Graphene. With the proposed technique the isolation between the radiating elements was improved on average by 22.5 dB compared to a reference array antenna with no SIW isolation. The performance of the array was enhanced by transforming the patch to exhibit metamaterial characteristics. This was achieved by embedding the patch antennas in the array with sub-wavelength slots. Compared to the reference array the metamaterial inspired structure exhibits improvement in isolation, radiation gain and efficiency on average by 28 dB, 6.3 dBi, and 34%, respectively. These results show the viability of proposed approach in developing antenna arrays for application in sub-THz integrated circuits.

scholarly journals Fast 3D Pattern Synthesis with Polarization and Dynamic Range Ratio Control for Conformal Antenna Arrays

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Massimiliano Comisso ◽  
Roberto Vescovo
Keyword(s):  
Antenna Arrays ◽  
Dynamic Range ◽  
Polarization State ◽  
Field Pattern ◽  
Pattern Synthesis ◽  
Conformal Antenna ◽  
Cpu Time ◽  
Conformal Arrays ◽  
Far Field Pattern ◽  
Joint Pattern

This paper proposes an iterative algorithm for the 3D synthesis of the electric far-field pattern of a conformal antenna array in the presence of requirements on both the polarization and the dynamic range ratio (DRR) of the excitations. Thanks to the use of selectable weights, the algorithm allows a versatile control of the DRR and of the polarization in a given angular region and requires a low CPU time to provide the array excitations. Furthermore, a modified version of the algorithm is developed to enable the optimization of the polarization state by phase-only control. Numerical results are presented to verify the usefulness of the proposed approach for the joint pattern and polarization synthesis of conformal arrays with reduced or even unitary DRR.

scholarly journals Reconstruction of the near-field distribution in an X-ray waveguide array

2017 ◽  
Vol 50 (3) ◽  
pp. 701-711 ◽  
Author(s):  
Qi Zhong ◽  
Lars Melchior ◽  
Jichang Peng ◽  
Qiushi Huang ◽  
Zhanshan Wang ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Field Distribution ◽  
Phase Retrieval ◽  
Near Field ◽  
Field Pattern ◽  
Waveguide Array ◽  
X Ray ◽  
Field Patterns ◽  
Thickness Variations ◽  
Far Field Pattern

Iterative phase retrieval has been used to reconstruct the near-field distribution behind tailored X-ray waveguide arrays, by inversion of the measured far-field pattern recorded under fully coherent conditions. It is thereby shown that multi-waveguide interference can be exploited to control the near-field distribution behind the waveguide exit. This can, for example, serve to create a secondary quasi-focal spot outside the waveguide structure. For this proof of concept, an array of seven planar Ni/C waveguides are used, with precisely varied guiding layer thickness and cladding layer thickness, as fabricated by high-precision magnetron sputtering systems. The controlled thickness variations in the range of 0.2 nm results in a desired phase shift of the different waveguide beams. Two kinds of samples, a one-dimensional waveguide array and periodic waveguide multilayers, were fabricated, each consisting of seven C layers as guiding layers and eight Ni layers as cladding layers. These are shown to yield distinctly different near-field patterns.

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.

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