Efficient Sampling of the Near Field Radiated by a Planar Source: Numerical Results

2019 ◽  
Author(s):  
M. A. Maisto ◽  
R. Solimene ◽  
R. Pierri
Keyword(s):  
Near Field ◽  
Numerical Results ◽  
Efficient Sampling ◽  
Planar Source

Near-Field Transverse Resolution in Planar Source Reconstructions

2021 ◽  
pp. 1-1
Author(s):  
Maria Antonia Maisto ◽  
Rocco Pierri ◽  
Raffaele Solimene
Keyword(s):  
Near Field ◽  
Planar Source ◽  
Transverse Resolution

RADIATED ACOUSTIC PRESSURE FROM A MOVING, NONUNIFORMLY VIBRATING CYLINDER WITH TWO SPHERICAL ENDCAPS

1994 ◽  
Vol 02 (01) ◽  
pp. 71-82 ◽  
Author(s):  
ZHAOXI WANG ◽  
SEAN F. WU
Keyword(s):  
Near Field ◽  
Translational Motion ◽  
Normal Component ◽  
Forward Direction ◽  
Numerical Results ◽  
Surface Velocity ◽  
Reverse Direction ◽  
Far Field ◽  
Field Source ◽  
Sound Diffraction

This paper presents numerical results of radiated acoustic pressures from a moving, nonuniformly vibrating cylinder with two spherical endcaps, based on an extended Kirchhoff integral formulation. Specifically, we consider cases in which the normal component of the surface velocity is nonzero on a portion of the surface, and zero elsewhere. Numerical results demonstrate that the radiation patterns depend critically on the frequency and source dimensions. For a noncompact source, the strongest radiation may not necessarily stem from a vibrating surface, but rather from a nonvibrating surface due to the effect of sound diffraction. The more noncompact the source is, the larger the number of side lobes in the near field and the more concentrated these side lobes will be. In the far field, however, the side lobes become smeared and less distinguishable. In other words, the effect of sound diffraction is greatly reduced in the far field. Source translational motion induces sound radiation in the perpendicular direction and enhances the radiated acoustic field in general. Enhancement in the forward direction is much greater than in the reverse direction.

scholarly journals A Generalized case of Electromagnetic Scattering from a finite number of Ferromagnetic cylinders

2015 ◽  
Vol 4 (3) ◽  
pp. 8 ◽  
Author(s):  
T. Kumar ◽  
N. Kalyanasundaram ◽  
B. K. Lande
Keyword(s):  
Finite Number ◽  
Electromagnetic Scattering ◽  
Scattered Field ◽  
Near Field ◽  
Scattering Problem ◽  
Normal Incidence ◽  
Generalized Solution ◽  
Numerical Results ◽  
Infinite Length ◽  
Angle Of Incidence

A generalized solution of the scattering problem from an array containing a finite number of axially magnetized ferromagnetic cylinders of infinite length placed in free space is presented in this paper. The analysis is carried out by matching the tangential boundary conditions at the surface of each cylinder to find the unknown expansion coefficients of the scattered field. Planar arrays consist of a finite number of ferromagnetic microwires are considered to obtain the numerical results for TMz and TEz polarizations in terms of the variation in scattered field components of the near field and scattering cross section (SCS) with respect to angle of incidence, radius of microwires, spacing among the microwires and operating frequency. For validation purpose, numerical results of the proposed analysis specialized for the case of single microwire and normal incidence for TMz polarization are compared with the results available in the literature for the specialized case and both are found to be matched completely.

scholarly journals Design and Study of a Wide-Band Printed Circuit Board Near-Field Probe

Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2201 ◽  
Author(s):  
Pedro A. Martinez ◽  
Enrique A. Navarro ◽  
Jorge Victoria ◽  
Adrian Suarez ◽  
Jose Torres ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Interference ◽  
Printed Circuit Board ◽  
Transmission Loss ◽  
Near Field ◽  
Fem Simulation ◽  
Numerical Results ◽  
Circuit Board ◽  
Frequency Range ◽  
Printed Circuit

Magnetic near-field probes (NFP) represent a suitable tool to measure the magnetic field level from a small electromagnetic interference (EMI) source. This kind of antenna is useful as a magnetic field probe for pre-compliance EMC measurements or debugging tasks since the user can scan a printed circuit board (PCB) looking for locations with strong magnetic fields. When a strong H-field point is found, the designer should check the PCB layout and components placement in that area to detect if this could result in an EMI source. This contribution focuses on analyzing the performance of an easy to build and low-cost H-field NFP designed and manufactured using a standard PCB stack-up. Thereby, the frequency range and sensitivity of the NFP-PCB are analyzed through a Finite Element Method (FEM) simulation model that makes it possible to evaluate its sensibility and effective frequency range. The numerical results obtained with the FEM models are validated against measurements to verify the design and performance of our NFP. The FEM model reproduces the experimental procedure, which is used to evaluate the performance of the NFP in terms of sensitivity by means of the simulated near-field distribution. The NFP-PCB has almost a flat response from 180 MHz to 6 GHz, with an almost perfect concordance between numerical and experimental S21 results. The numerical results show an average transmission loss of −27.9 dB by considering the flat response bandwidth, whereas the experimental one is −29.7 dB. Finally, the designed NFP is compared to two high-quality commercial probes in order to analyze its performance.

scholarly journals Near-Field Warping Sampling Scheme for Broad-Side Antenna Characterization

Electronics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1047
Author(s):  
Maria Maisto ◽  
Rocco Pierri ◽  
Raffaele Solimene
Keyword(s):  
Near Field ◽  
Singular Values ◽  
Sampling Theorem ◽  
Sampling Scheme ◽  
Limited Function ◽  
Field Radiation ◽  
Planar Source ◽  
Standard Sampling ◽  
Band Limited ◽  
Band Limited Function

In this paper the problem of sampling the field radiated by a planar source observed over a finite planar aperture located in the near-field is addressed. The problem is cast as the determination of the spatial measurement positions which allow us to discretize the radiation problem so that the singular values of the radiation operator are well-approximated. More in detail, thanks to a suitably warping transformation of the observation variables, the kernel function of the relevant operator is approximated by a band-limited function and hence the sampling theorem applied to achieved discretization. It results in the sampling points having to be non-linearity arranged across the measurement aperture and their number can be considerably lowered as compared to more standard sampling approach. It is shown that the proposed sampling scheme works well for measurement apertures that are not too large as compared to the source’s size. As a consequence, the method appears better suited for broad-side large antenna whose radiated field is mainly concentrated in front of the antenna. A numerical analysis is included to check the theoretical findings and to study the trade-off between the field accuracy representation (over the measurement aperture) and the truncation error in the estimated far-field radiation pattern.

Phaseless Synthetic Aperture Radar With Efficient Sampling for Broadband Near-Field Imaging: Theory and Validation

2015 ◽  
Vol 63 (2) ◽  
pp. 573-584 ◽  
Author(s):  
Jaime Laviada ◽  
Ana Arboleya-Arboleya ◽  
Yuri Alvarez-Lopez ◽  
Cebrian Garcia-Gonzalez ◽  
Fernando Las-Heras
Keyword(s):  
Synthetic Aperture Radar ◽  
Near Field ◽  
Synthetic Aperture ◽  
Near Field Imaging ◽  
Efficient Sampling ◽  
Imaging Theory ◽  
Field Imaging ◽  
Aperture Radar

Extended Kirchhoff Integral Formulations for Sound Radiation from Vibrating Cylinders in Motion

1993 ◽  
Vol 115 (3) ◽  
pp. 324-331 ◽  
Author(s):  
S. F. Wu ◽  
Z. Wang
Keyword(s):  
Acoustic Pressure ◽  
Near Field ◽  
Translational Motion ◽  
Sound Radiation ◽  
Forward Direction ◽  
Numerical Results ◽  
Rectilinear Motion ◽  
Dimensionless Frequency ◽  
Translational Speed ◽  
Kirchhoff Integral

This paper presents numerical results of sound radiation from vibrating cylinders in rectilinear motion at constant subsonic speeds by using the extended Kirchhoff integral formulations recently derived by Wu and Akay (1992). In particular, the effects of the interaction between the turbulent stress field and the vibrating surface in motion are examined. Numerical results demonstrate that this interaction is significant in the near-field when the dimensionless frequency ka > 2 and the dimensionless source translational speed M > 0.1. If this interaction is completely neglected, the predicted acoustic pressure is underestimated by as much as 10 to 20 percent in the near field. The effects of this interaction, however, decrease in the far-field. The effects of surface translational motion on the resulting sound radiation are also examined. It is found that the surface translational motion has a significant effect on the resulting sound generation in both near- and far-fields. The amplitude of the acoustic pressure is approximately doubled in the forward direction when ka > 2 and M > 0.2, which corresponds to at least a 5 dB increase in the SPL value.

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