1,721,054 research outputs found
Near-field far-field transformation from nonredundant plane-polar data: Effective modellings of the source
No full textRepresentation of electromagnetic fields over arbitrary surfaces by a finite and non redundant number of samples
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Scattering from a 90◦ Metallic Wedge with One Face Coated by a Double Negative Metamaterial Layer
No full text—This manuscript refers to the electromagnetic scattering problem involving plane waves at skew incidence with respect to the edge of a right-angled metallic wedge having one face coated by a double negative metamaterial sheet. Its presence in the propagation scenario is properly accounted at high frequencies by considering the geometrical optics response of the structure and the diffraction contribution arising from the edge of the wedge. In particular, the reflection coefficients related to the coated surface are determined for both the polarizations by using the equivalent transmission line circuit, whereas the diffraction coefficients are obtained by applying the uniform asymptotic physical optics approach. This last is based on electric and magnetic equivalent surface currents under the physical optics approximation and permits to evaluate the diffraction contribution in the context of the uniform geometrical theory of diffraction. The resulting approximate solution is characterized by the same simplicity of use of the heuristic solutions and provides reliable field values as confirmed by the numerical tests carried out by a full-wave commercial software
Field reconstruction over a cylinder from a non-redundant number of samples over a non-uniform circular helix
No full textA Nonredundant Sampling Representation Managing an Offset Mounting of an Elongated Antenna in a Spherical Near-Field Facility
No full textAn efficient spherical near-field-to-far-field transformation (NFTFFT), which takes into account the offset mounting of an elongated antenna and employs the same nonredundant (NR) amount of near-field (NF) data as in the onset mounting case, is presented. The interest for this NFTFFT is due to the fact that, for practical reasons, a mounting where the antenna and the scan sphere centers coincide is not always possible. In this case, the amount of NF measurements required by the traditional spherical NFTFFT can significantly increase. In the developed NFTFFT, this drawback has been overcome by accurately recovering these NF data from the gathered NR probe voltage samples through a sampling expansion, attained by suitably using the NR sampling representations and assuming the antenna as enclosed in a prolate spheroid. Numerical and experimental results are reported in order to assess the efficacy of the developed technique
A Non-Redundant Hemi-Spherical Scanning for Automotive Antenna Near-Field Measurements
No full textA non-redundant sampling representation of the probe voltage is proposed to reduce the number of needed near-field data for hemi-spherical antenna measurements in an automotive testing set-up with a flat metallic ground. This last is taken into account by employing the image principle. The approach benefits from a useful modeling of the radiating system including many RF sub-systems and the host vehicle. An adaptable convex surface containing the entire radiating system and its image is chosen as source modeling and the optimal parameters are determined for applying the corresponding sampling and interpolation algorithms. Accordingly, the procedure allows one to reconstruct the voltage values on the near-field hemi-sphere from the knowledge of a minimum number of data. It is obvious that the reduction of the collected data implies a saving of the acquisition time in the testing process
NF-FF transformation with cylindrical scanning: an effective technique for elongated antennas
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An effective iterative algorithm to correct the probe positioning errors in a non-redundant plane-rectangular near-field to far-field transformation
No full textAn algorithm for the effective compensation of known positioning errors, affecting the samples acquired by the probe in a non-redundant plane-rectangular (PR) near-field to far-field (NFFF) transformation, is presented and fully assessed by experimental tests. This transformation adopts a non-conventional PR scan, named planar wide-mesh scan (PWMS), characterized by meshes widening more and more as their distance from the measurement plane center increases, and uses a nonredundant sampling representation of the probe voltage. Such a representation is obtained by considering the antenna as contained in an oblate spheroid, to precisely determine the input NF data for the traditional PR NFFF transformation from the PWMS samples. These samples are unavailable in presence of positioning errors, but, as it will be shown, can be effectively retrieved from the errors affected ones by applying an iterative procedure
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