1,721,039 research outputs found
Sparsity of the Field Signal-Based Method for Improving Spatial Resolution in Antenna Sensor Array Processing
Full text linkThe goal of array processing is to gather information from propagating radio-wave signals, as their Direction Of Arrival (DOA). The estimation of the DOA can be carried out by extracting the information of interest from the steering vector relevant to the adopted antenna sensor array. Such task can be accomplished in a number of different ways. However, in source estimation problems, it is essential to make use of a processing algorithm which feature not only good accuracy under ideal working conditions, but also robustness against non-idealities such as noise, limitations in the amount of collectible data, correlation between the sources, and modeling errors. In this work particular attention is devoted to spectrum estimation approaches based on sparsity. Conventional algorithms based on Beamforming fail wherein the radio sources are not within Rayleigh resolution range which is a function of the number of sensors and the dimension of the array. DOA estimation techniques such as MUSIC (MUltiple Signal Classifications) allow having a larger spatial resolution compared to Beamforming-based procedures, but if the sources are very close and the Signal to Noise Ratio (SNR) level is low, the resolution turns to be low as well. A better resolution can be obtained by exploiting sparsity: if the number of sources is small, the power spectrum of the signal with respect to the location is sparse. In this way, sparsity can enhance the accuracy of the estimation. In this paper, an estimation procedure based on the sparsity of the radio signals and useful to improve the conventional MUSIC method is presented and analyzed. The sparsity level is set in order to focus the signal energy only along the actual direction of arrival. The obtained numerical results have shown an improvement of the spatial resolution as well as a reduced error in DOA estimation with respect to conventional techniques
Non-Invasive Reflectometry-Based Detection of Melanoma by Piezoelectric Micro-Needle Antenna Sensors
Full text linkThe electromagnetic characterization of piezoelectric micro-needle antenna sensors for fully non-invasive detection of cancer-related anomalies of the skin is presented. To this end, a full-wave finite-difference time-domain procedure is adopted to analyze the performance of the considered class of devices in terms of circuital characteristics and near-field radiation properties as a function of the curvature radius of the relevant sensing probe. This analysis is, in turn, useful to gain a physical insight into the processes which affect the behavior of the structure and, hence, the accuracy in the detection of possible malignant lesions of the skin. In particular, by using the mentioned modeling approach, an extensive parametric study is carried out to analyze the effect produced on the sensor response by variations of the complex permittivity of the skin due to the presence of anomalous cells and, in this way, obtain useful discrimination diagrams
for the heuristic evaluation of the exposure level to the cancer risk
Solution of the Dirichlet problem for the Laplace equation in general cylinder.
No full textWe consider the Dirichlet problem for the Laplace equation in a bounded cylindrical domain C:=D , where D is a starlike domain of the (x,y)-plane. We show how to construct the solution by using the Fourier series method. We derive some numerical results defining by means of the so called “superformula” introduced by J.Gielis. By using a computer algebra system we find a quite rapid convergence of the approximate solutions to the real one, with only possible exceptions corresponding to singular points in which oscillations recalling Gibbs’ phenomenon appear. Our findings are in agreement with the theoretical results on Fourier series due to L.Carleson
Design and Full-Wave Analysis of Piezoelectric Micro-Needle Antenna Sensors for Enhanced Near-Field Detection of Skin Cancer
Full text linkThe design and full-wave analysis of piezoelectric micro-
needle antenna sensors for minimally invasive near- ̄eld detection of cancer-related anomalies of the skin is presented. To this end, an accurate locally conformal ̄nite-di®erence time-domain procedure is adopted. In this way, an insightful understanding of the physical processes detecting the characteristics of the considered class of devices is achieved. This is important to improve the structure reliability, so optimizing the design cycle. In this regard, a suitable sensor layout is described, and discussed in detail. The major benefit of the proposed system stems from the potential for obtaining a superior performance in terms of input impedance matching and efficiency, in combination with an electronically tunable steering property of the near-field radiation intensity which can be profitably used to
enhance the illumination and, hence, the localization of possible
malignant lesions in the host medium. By using the detailed modeling approach, an extensive parametric study is carried out to analyze the effect produced on the sensor response by variations of the complex permittivity of the skin due to the presence of anomalous cells, and thus useful heuristic discrimination formulas for the evaluation of the exposure level to cancer risk are derived
Fourier solution of the wave equation for a starlike shaped vibrating membrane
No full textAbstractThe Fourier solution of the wave equation for a circular vibrating membrane is generalized to a star-like-shaped structure. We show that the classical solution can be used in this more general case, provided that a suitable change of variables in the spherical co-ordinate system is performed
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