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An investigation of curved contoured beam reflectarrays with reusable surface for multiple coverages is presented. The main advantage of curved reflectarrays over shaped reflectors is that they allow the possibility of reusing a standard parabolic mold for multiple missions. To demonstrate this, two curved reflectarrays are designed using the direct optimization technique to fulfill the requirements...
Two techniques are compared for the crosspolar optimization of reflectarray antennas using a full-wave analysis technique based on local periodicity directly in the optimization process within acceptable computing time. The first one is based on the Levenberg-Marquardt Algorithm (LMA) while the second technique is based on the generalized Intersection Approach framework using the LMA as backward projector...
A gradient index lens is designed by utilizing quasi-conformal transformation electromagnetics (QCTEM) to define the index distribution in a rotationally symmetric lens. The smooth and continuous nature of QCTEM is investigated and an analytical surrogate model is trained to replace the computationally intensive QCTEM procedure and ray trace simulations. The surrogate model is then incorporated into...
Future 5G backhaul networks in dense small cell deployments will require high gain antennas with beam- and null-steering capabilities. In this framework this paper analyzes the null-steering capabilities of reflectarray antennas, as a low cost alternative to traditional antenna arrays. In particular, a random search algorithm is used to show that null-steering can be performed even with 1-bit reflectarrays,...
This paper evaluates different analog-digital beam-forming solutions for future spectrum sharing mm-wave scenarios. In contrast to sub-6 GHz multiantenna schemes where all-digital solutions provide an excellent performance-cost tradeoff, in the mm-wave bands where a very large number of antennas is required, all-digital designs cannot be deployed due to their cost and complexity. In order to solve...
A reconfigurable over-the-air chamber represents a reverberation chamber whose walls are lined with antennas that are terminated in reconfigurable impedances, allowing synthesis of a wide range of channel conditions for over-the-air testing of mobile wireless devices. While these chambers have potential for practical device testing, finding the right impedances to achieve the desired channel characteristics...
3D field shaping is a canonical problem in wave physics that could impact next generation of therapeutic systems. In this framework, we present an innovative and effective strategy that relies on the convex relaxation of the original NP hard problem by taking inspiration from the optimal constrained power focusing method. The formulation presented in this paper in terms of convex programming allows...
In this work the problem of synthesizing the excitations of a linear array, clustered into contiguous sub-arrays of irregular length, is addressed. By suitably exploiting the behavior of clustered array aperture distributions (i.e., step-wise discrete functions), the problem has been formulated as the minimization of the total variation (TV) of the excitations, satisfying a matching condition on a...
Near-field shaping at microwave or millimeter wave frequencies is an emerging field of study, able to accelerate a variety of technologies. Applications from sensing to medical imaging will benefit from accurate near-field shaping methods. In this communication, the use of convex optimization to shape the near field of a flat radiating aperture is investigated. The proposed approach, that is known...
A position shift method (PSM) is presented for uniform planar array pattern synthesis in this paper. This method minimizes the sidelobe level (SLL) by searching the best position solution for every sensor and calculating the pattern with position offset factor. The position offset factor will be calculated by the position shift value without changing the physical geometry. Numerical examples show...
The design of an aperiodic frequency selective surface (FSS) for compact quasi-optical networks is presented in this paper. Using a newly developed Physical Optics (PO) method in conjunction with a direct optimisation approach where all elements are simultaneously optimised, an FSS with an aperiodic element layout operating in several discrete bands over the frequency range 23–230 GHz has been designed...
Frequency-diverse imaging is an all-electronic method, capable of sampling the scene to be imaged without the need for a mechanical scan or active circuit components. In order to optimize the imaging characteristics, such as imaging resolution and fidelity of the reconstructed images, the antennas used within this scheme need to be optimized. It is demonstrated that using a Mills-Cross iris distribution,...
A volume pixel subspace-based optimization method (SOM) is proposed to solve the electromagnetic imaging of the wave impenetrable objects/perfect electric conductor (PEC). In this proposed method, the PEC objects are approximated by highly lossy dielectric scatterers with pure imaginary permittivity and thus volume pixel SOM is successfully employed. There is no prior information such as the number...
The paper deals with the extensive use of optimization techniques at Space Engineering during the several phases of development of antenna sub-systems for satellite applications.
Cyber-Physical System (CPS) applications in lower-extremity bony-fracture rehabilitation systems require real-time biophysical data. Emerging and interesting solutions are microwave approaches that provide good contrast between hard and soft tissues and between local anomalies inside tissues. Preliminarily some contacting non-invasive planar methods have been investigated in their feasibility of detecting...
An ultra-wideband linear polarization converting metasurface is presented. The polarizer is based on a periodic arrangement of metallic elements printed on a grounded dielectric substrate. The element geometry of the metasurface is optimized with a genetic algorithm by discretizing the unit cell in a 16×16 pixel matrix. This polarization converter is able to work from 7.03 GHz to 29.01 GHz (121% of...
We present a new type of pixel antennas involving hexagonal unit cells that are suitable for fabrication in low-cost inkjet-printing setups. Antennas are optimized in a rigorous simulation environment based on the multilevel fast multipole algorithm integrated into genetic algorithms. Hexagonal cells are suitable for both the optimization environment and fabrication setup. Optimizations are performed...
This paper presents a study of the efficacy of different optimization strategies for location tracking on an Android App that is run on a smartphone. The basic algorithm determines the most probable path of the user within a WiFi network by comparing raw RSSI measurements at each location with values in a fingerprint database. The investigated optimization strategies include: accounting for previous...
Energy-efïîdent planning is a current challenge for heterogeneous 4g wireless networks, since ‘greener’ strategies typically act against the always growing traffic requirements. However, network-wide optimization of base station antenna patterns can be exploited to that end, leading the total transmit power of the network to a global minimum. This article formulates the coverage and capacity optimization...
A synthesis of a GA and an EM application to guide the design and optimisation of tightly coupled phased array antennas is proposed. Some analysis and tested results are provided. This technique is biased to satisfy certain desired specifications subject to the mid-frequency SKA radio astronomy. Tightly coupled arrays are a practical realisation of the current sheet model (CSA) for an array with a...
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