Design of a small-size, low-profile, and low-cost normal-mode helical antenna for UHF RFID wristbands

Emerging RFID applications in the UHF band in some cases require very specific antenna solutions. This letter considers the identification and tracking of patients inside hospital facilities using wristbands, which impose strict tag size and cost limitations. We propose a solution for passive tags based on a normal-mode helical antenna as an alternative to bulky and/or expensive solutions that can be found in the literature. The robustness of the resulting wristband will be assessed in a particular implementation by measuring the maximum read range for a variety of subjects with different physical constitutions

Performance assessment of a novel miniaturized RFID tag for inventorying and tracking metallic tools

This contribution proposes a novel radio frequency identification tag antenna operating in the EU UHF band (865-868 MHz). Miniaturization techniques have been used to achieve a reduced volume (20 × 2.56 × 3 mm 3 ) in order to make it suitable for labeling metallic tools. Simulations are used to assess the tag performance when operating on tools of different sizes. These simulations are validated through measurements in a reference scenario (anechoic chamber). Finally, a real scenario (tool hanging board) is considered in order to evaluate tag performance when interacting with other tags and tools

Integral equation mei applied to three-dimensional arbitrary surfaces

The authors present a new formulation of the integral equation of the measured equation of invariance (MEI) as a confined field integral equation discretised by the method of moments, in which the use of numerically derived testing functions results in an approximately sparse linear system with storage memory requirements and a CPU time for computing the matrix coefficients proportional to the number of unknowns.Peer ReviewedPostprint (published version

Analysis of microstrip antennas by multilevel matrix decomposition algorithm

Integral equation methods (IE) are widely used in conjunction with Method of Moments (MoM) discretization for the numerical analysis of microstrip antennas. However, their application to large antenna arrays is difficult due to the fact that the computational requirements increase rapidly with the number of unknowns N. Several techniques have been proposed to reduce the computational cost of IE-MoM. The Multilevel Matrix Decomposition Algorithm (MLMDA) has been implemented in 3D for arbitrary perfectly conducting surfaces discretized in Rao, Wilton and Glisson linear triangle basis functions . This algorithm requires an operation count that is proportional to N·log2N. The performance of the algorithm is much better for planar or piece-wise planar objects than for general 3D problems, which makes the algorithm particularly well-suited for the analysis of microstrip antennas. The memory requirements are proportional to N·logN and very low. The main advantage of the MLMDA compared with other efficient techniques to solve integral equations is that it does not rely on specific mathematical properties of the Green's functions being used. Thus, we can apply the method to interesting configurations governed by special Green's functions like multilayered media. In fact, the MDA-MLMDA method can be used at the top of any existing MoM code. In this paper we present the application to the analysis of large printed antenna arrays.Peer ReviewedPostprint (published version

On the testing of the magnetic field integral equation with RWG basis functions in method of moments

For electromagnetic analysis using method of moments (MoM), three-dimensional (3-D) arbitrary conducting surfaces are often discretized in Rao, Wilton and Glisson basis functions. The MoM Galerkin discretization of the magnetic field integral equation (MFIE) includes a factor Ω0 equal to the solid angle external to the surface at the testing points, which is 2π everywhere on the surface of the object, except at the edges or tips that constitute a set of zero measure. However, the standard formulation of the MFIE with Ω0=2π leads to inaccurate results for electrically small sharp-edged objects. This paper presents a correction to the Ω0 factor that, using Galerkin testing in the MFIE, gives accuracy comparable to the electric field integral equation (EFIE), which behaves very well for small sharp-edged objects and can be taken as a referencePeer Reviewe

Figure of merit for multiband antennas

This communication defines a figure of merit for multiband antennas that gives an objective quantification of the similarities between radiation patterns at the different antenna operating bands.Peer Reviewe

Method of moments enhancement technique for the analysis of Sierpinski pre-fractal antennas

The numerical analysis of highly iterated Sierpinski microstrip patch antennas by method of moments (MoM) involves many tiny subdomain basis functions, resulting in a very large number of unknowns. The Sierpinski pre-fractal can be defined by an iterated function system (IFS). As a consequence, the geometry has a multilevel structure with many equal subdomains. This property, together with a multilevel matrix decomposition algorithm (MLMDA) implementation in which the MLMDA blocks are equal to the IFS generating shape, is used to reduce the computational cost of the frequency analysis of a Sierpinski based structure.Peer Reviewe

Star-shaped wheel for mechanical micro-Doppler modulation

This letter investigates the possibility of using deliberated geometries for rotating targets, which may improve the detectability and classification by means of its micro-Doppler signature. Beyond the signature provided by the rotation rate of the target, every particular geometry leads to specific and unique modulation waveforms that increase the information related to this target. Different star-shaped wheels with particular geometries have been designed demonstrating different reflection characteristics and modulation waveforms. The signature of these rotating star-shaped wheels has been measured in an anechoic chamber using a general-purpose 24 GHz frequency-modulated continuous wave (FMCW) radar platform and a detection algorithm based on the derivative of the cross-correlation is proposed to validate the proposed approach

Fast direct solution of method of moments linear system

A novel algorithm, the compressed block decomposition (CBD), is presented for highly accelerated direct (non iterative) method of moments (MoM) solution of electromagnetic scattering and radiation problems. The algorithm is based on a block-wise subdivision of the MoM impedance matrix. Impedance matrix subblocks corresponding to distant subregions of the problem geometry are not calculated directly, but approximated in a compressed form. Subsequently, the matrix is decomposed preserving the compression. Examples are presented of typical problems in the range of 5000 to 70 000 unknowns. The total execution time for the largest problem is about 1 h and 20 min for a single excitation vector. The main strength of the method is for problems with multiple excitation vectors (monostatic RCS computations) due to the negligible extra cost for each new excitation. For radiation and scattering problems in free space, the numerical complexity of the algorithm is shown to be N2 and the storage requirements scale with N3/2.Peer Reviewe

Modelado circuital de diferentes configuraciones de antenas microstrip

L'objectiu del projecte es facilitar el disseny i la modificació d'antenes microstrip utilitzant models circuitals. En el document s'exposa conjuntament la teoria de vàries configuracions d'antenes microstrip dispersa en varis documents i les equacions més rellevants per l'anàlisi dels fenòmens que es produeixen en cada model d'antena amb l'objectiu de realitzar un estudi detallat de les tendències dels components de cada configuració. L'estudi de les tendències es realitza per obtenir una relació entre els paràmetres físics i els components dels models circuitals proposats per a cada configuració d'antena microstrip. Utilitzant la teoria exposada en el document i l'estudi realitzat es comprova que és possible facilitar i realitzar modificacions en el disseny d'antenes microstrip mitjançant els models circuitals proposats.El objetivo del proyecto es facilitar el diseño y la modificación de antenas microstrip utilizando modelos circuitales. En el documento se expone conjuntamente la teoría de varias configuraciones de antenas microstrip dispersa en varios documentos y las ecuaciones más relevantes para el análisis de los fenómenos que se producen en cada modelo de antena con el objetivo de realizar un estudio detallado de las tendencias de los componentes de cada configuración El estudio de las tendencias se realiza para obtener una relación entre los parámetros físicos y los componentes de los modelos circuitales propuestos para cada configuración de antena microstrip. Utilizando la teoría expuesta en el documento y el estudio realizado se comprueba que es posible facilitar y realizar modificaciones en el diseño de antenas microstrip mediante los modelos circuitales propuestos.The goal of this project is to facilitate the design and modification of microstrip antennas using circuit models. The document presents together the theory of various configurations of microstrip antennas scattered in various documents and relevant equations for the analysis of the phenomenon that occur in each antenna model in order to realize a detailed study of the trends of the components of each configuration. The study of the trends is made to obtain a relationship between the physical parameters and components of the proposed circuit models for each microstrip antenna configuration. Using the exposed theory in the document and the realized study it is proved that it is possible to facilitate and make changes in the design of microstrip antennas using the proposed circuit models