Application of Nonredundant Sampling Representations of Electromagnetic Fields to NF-FF Transformation Techniques

An overview of the application of the band-limitation properties and nonredundant sampling representations of electromagnetic fields to NF-FF transformations is presented. The progresses achieved by applying them to data acquired on conventional NF scanning surfaces are discussed, outlining the remarkable reduction in the number of needed NF samples and measurement time. An optimal sampling interpolation expansion for reconstructing the probe response on a rotational scanning surface from a non-redundant number of its samples is also discussed. A unified theory of the NF-FF transformations with spiral scannings, which allow a remarkable reduction of the measurement time, is then reviewed by describing a sampling representation of the voltage on a quite arbitrary rotational surface from its nonredundant samples collected on a proper spiral wrapping it. Some numerical and experimental results assessing the effectiveness of the considered NF-FF transformations are shown too

Near-Field/Far-Field Transformation with Helicoidal Scanning from Irregularly Spaced Data

A fast and accurate technique for the compensation of the probe positioning errors in the near-field/far-field transformation with helicoidal scanning is proposed in this paper. It relies on a nonredundant sampling representation using a spherical modelling of the antenna under test and employs an iterative scheme to evaluate the near-field data at the points fixed by the helicoidal nonredundant representation from the acquired irregularly distributed ones. Once these helicoidal data have been recovered, those required by a classical cylindrical near-field/far-field transformation are efficiently determined by using an optimal sampling interpolation algorithm. Some numerical tests assessing the effectiveness of the proposed approach and its stability with respect to random errors affecting the near-field data are shown

Izračun izračene snage iz rezulata mjerenja u bliskom polju dobivenih metodom uzorkovanja na planarnoj širokoj mreži

A full procedure is developed in this paper for evaluating the power radiated by an antenna under test from a nonredundant number of near-field measurements collected by the innovative planar wide-mesh scanning. It can be applied for the antenna directivity evaluation whenever the power radiated by the antenna in the backward half-space is negligible. Such a procedure makes use of a closed form formula for computing the total radiated power from the knowledge of the radiation intensity samples on the far-field sphere. These samples are determined via a probe compensated near-field — far-field transformation. An optimal sampling interpolation formula is also used for their evaluation. The effectiveness of the proposed procedure is assessed by numerical simulations.U radu je razvijena potpuna procedura za izračun snage koju zrači ispitna antena. Procedura je zasnovana na neredundantnim mjerenjima u bliskom polju na osnovi inovativnog uzorkovanja na planarnoj širokoj mreži. Metoda se može primijeniti za odredivanje usmjerenosti antene u slučajevima kada je zračenje u stražnji poluprostor zanemarivo. Metoda se zasniva na uporabi izraza za izračun ukupne izračene snage preko poznavanja izračene gustoće snage uzorkovane na sferi u dalekom polju. Ti uzorci su odredeni primjenom transformacije iz bliskog polja (kompeziranog zbog utjecaja mjerne sonde) u daleko polje. U predloženoj metodi takoder je rabljena optimalna interpolacijska formula za uzorkovanje. Efikasnost predložene metode razmatrana je numeričkim simulacijama

Whole Blood Transcriptome Characterization of 3xTg-AD Mouse and Its Modulation by Transcranial Direct Current Stimulation (tDCS)

The 3xTg-AD mouse is a widely used model in the study of Alzheimer’s Disease (AD). It has been extensively characterized from both the anatomical and behavioral point of view, but poorly studied at the transcriptomic level. For the first time, we characterize the whole blood transcriptome of the 3xTg-AD mouse at three and six months of age and evaluate how its gene expression is modulated by transcranial direct current stimulation (tDCS). RNA-seq analysis revealed 183 differentially expressed genes (DEGs) that represent a direct signature of the genetic background of the mouse. Moreover, in the 6-month-old 3xTg-AD mice, we observed a high number of DEGs that could represent good peripheral biomarkers of AD symptomatology onset. Finally, tDCS was associated with gene expression changes in the 3xTg-AD, but not in the control mice. In conclusion, this study provides an in-depth molecular characterization of the 3xTg-AD mouse and suggests that blood gene expression can be used to identify new biomarkers of AD progression and treatment effects

Wave Diffraction by Metamaterial-Coated Wedges: The UAPO Solution for Skew Incidence

The interaction between an electromagnetic plane wave and a metallic wedge coated with a uniform layer made of a double-negative metamaterial is studied by means of the uniform asymptotic physical optics method in the high-frequency range, e.g., at microwave and optical frequencies. The apex angle of the structure is arbitrarily chosen, and the wave is at a skew incidence with respect to the external edge, which is formed by the metamaterial layers covering the wedge faces. The proposed method is built on the scattering integral involving electric and magnetic surface currents as physical optics equivalent sources, and it takes advantage of analytic evaluations. The last step uses a uniform asymptotic procedure to obtain a closed form expression of the diffracted field to be added to the geometrical optics one for computing the total field at the observation point in the neighboring free space. The study also includes a numerical validation of the method