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Herein, A new differential magnetic-field probe with parasitic elements is presented. The proposed probe has two pairs of shorted differential loops as parasitic elements, which could enhance the detection sensitivity owing to the increased detection area. The proposed probe comprises a U-shaped loop with two outputs as the driven element, two pairs of shorted differential loops as parasitic elements, a pair of shorted via, a pair of connected via, and many shielded vias. First, the usual single-loop probe is theoretically studied. Second, a pair of shorted loops is inserted into the differential single-loop probe as a parasitic element to receive more magnetic flux. Third, another pair of shorted loops is etched into the probe to further improve the detection sensitivity. The corresponding simulation results are presented to prove the effectiveness of the design. Finally, the proposed probe with parasitic elements is designed, printed, and evaluated. Measurement results reveal that the designed probe has high detection sensitivity.

Summary: Printed circuit boards play an increasingly important role in modern electronic systems. Equivalent dipole moments are widely used to reconstruct the radiated fields of printed circuit boards in view of the extremely high complexity. In this paper, an improved source reconstruction method based on complex‐valued neural network is proposed to investigate the radiation properties of printed circuit boards working in microwave frequency band. Firstly, the magnetic field data obtained from the near‐field scanning are utilized to construct a matrix equation based on the source reconstruction theory. Secondly, the kernel of the complex‐valued neural network is constructed through the algorithm of complex numbers, which eventually end up with the novel neural network with the help of the principle of regression optimization. Thirdly, the data obtained from the near‐field scanning are fed into the neural network for effective training to get the equivalent dipole model. Finally, several numerical examples and available measurement results are given to validate the method. Compared with the commonly used Tikhonov regularization method, the proposed method possesses higher accuracy and better robustness in noise suppression. [ABSTRACT FROM AUTHOR]

This article presents a novel and efficient batch data selection method based on active and unsupervised learning in real-time near-field scanning. The new approach shows a remarkable advantage over random sampling in reducing the number of scanning data samples and the total scanning time. Moreover, careful hyperparameter tuning is unnecessary, as the performance is insensitive to the hyperparameter values. After randomly selecting some initial points, three key steps are sequentially and iteratively implemented. First, the query-by-committee (QBC) method is adopted to evaluate the uncertainties of the unobserved positions using different interpolation functions and select an “uncertain” group with the largest variances. Second, the weighted K-means clustering (WKMC) method divides the “uncertain” group into multiple clusters and selects the representative samples by choosing the most uncertain point in each cluster to ensure diversity. Finally, an estimated variance change (EVC) method is proposed to select the most representative samples to enhance diversity further. The proposed approach of this article, referred to as the QWE (QBC + WKMC + EVC) method, can well balance uncertainty and diversity with high efficiency. The newly proposed QWE approach is validated in both simulations and measurements of near-field scanning. The batch data selection method of this article can be extended to other multidimensional regression modeling problems in which data acquisition is expensive. [ABSTRACT FROM AUTHOR]

In this paper, the methods of determining the bistatic radar cross sections (RCSs) of objects by near-field measurements with the use of a cylindrical scanner and further electromagnetic far-field calculations with the use of mathematical modeling are studied. In this case, an important problem is the possibility of scanning over a truncated surface instead of scanning over the entire one. Under such conditions, the results given by the classic method [1] become poorly predictable and the application of an adapted method is required. This paper develops the method in [2] as applied to a vector three-dimensional case. Two methods based on the serial expansion in cylindrical waves in the case of scanning over a truncated surface are compared: the classic method applied for the measurement of antenna radiation patterns (when the field outside the scanning area is set equal to zero) [1] and the proposed method, which strictly takes into account a truncated character of the scanning surface by angle. The comparison of calculation results confirms the method proposed in this paper is promising for application. [ABSTRACT FROM AUTHOR]

Near-field mapping along the surface of an integrated circuit (IC) could reveal the radiated emission source inside by collecting the radiated electromagnetic field. In this article, the radiated emission source localization is first illustrated in a microstrip line model by analyzing the relationship between the physical position of the line and the hot spots of the electromagnetic field distribution along the line surface. The hot spot in each magnetic field distribution does not necessarily correspond to the physical position of the emission source due to the ground plane below. Furthermore, by analogy with the microstrip line model, the localization analysis is applied to a large-scale IC [field-programmable gate array (FPGA)] in a ball grid array package. For the demonstration, four operation states of the FPGA are designed with four general-purpose input–output (GPIO) pins outputting waveforms of different frequencies. By activating the sources in different operation states, it is found that the activated GPIO pins (as emission sources) can be located well by comprehensively analyzing the emission patterns of different components. The experimental results would be instructive to improve the understanding of IC near-field electromagnetic patterns and reasonable to localize an emission source. [ABSTRACT FROM AUTHOR]

Despite their great potential in communication and sensing applications, printed leaky-wave antennas have rarely been reported at millimeter-wave (mm-wave) frequencies. In this article, tapered leaky-wave antennas operating at 80 GHz are designed, fabricated, and experimentally characterized. While many continuous leaky-wave antennas use subwavelength strips or other comparably small elements, in this work, the surface impedance is discretized very coarsely using only three square patches per period. With this architecture, a wide range of surface reactance can be achieved while maintaining a minimum feature size of the metallic pattern that is feasible for printed circuit fabrication. Another advantage of this approach over existing works in the mm-wave frequency range is that it allows precise engineering of the aperture illumination. We demonstrate this by applying amplitude tapering for sidelobe suppression. A comprehensive experimental study is presented, including near- and far-field measurements. Therewith, we verify the designed aperture illumination and reveal the origin of spurious far-field features. Sidelobes are effectively suppressed and spurious radiation is reduced to -18 dB compared to the main lobe. [ABSTRACT FROM AUTHOR]

Switched beam antennas provide an efficient and cost effective alternative to complex phased array and digital beam forming techniques. In this paper, we present the design and characterization of an electrically thin Huygens metasurface lens operating at 83GHz with high transmission efficiency and we demonstrate its applicability to switched beam antenna applications. We accurately characterize the 3D scattered field distribution and determine the focal length and transmission efficiency of the lens by near-field scanning. A model based on ideal Huygens sources is used to predict the focal performance, allowing the geometrical measurement parameters to be determined in advance. Finally, the ability of the lens to operate as a switched beam antenna is experimentally verified by exciting it with an omnidirectional waveguide antenna placed at different positions. The experimental results are in very good agreement with numerical simulations, showing steering angles up to 12° while keeping the side lobe level below -15dB.

The radiation emission from high-speed digital circuit may result in radio-frequency interference (RFI) problems in modern electronic devices. In this paper, an improved equivalent dipole source based on a new transfer model and a new regularization method is proposed. The equivalent source is obtained by solving an inverse equation with near-field data. The tangential component of electric field used in conventional equivalent source extraction is replaced by the normal component, which can reduce the test difficulty and enhance the measurement efficiency. The new regularization method based on Tikhonov and truncated singular value decomposition (TSVD) can enhance the stability and accuracy of the dipole solution. In addition, the new transfer model and regularization method are verified by simulations and measurements.

The electromagnetic interference (EMI) problems are crucial for system-in-package (SiP) due to the high demand of miniaturization and dense integration. Shielding methods are generally employed to protect SiP from EMI, through assessing the key performance index, i.e., shielding effectiveness (SE). In this article, the SE of a SiP is evaluated by using near-field scanning method. The SEs derived by using maximum near-field values and average near-field values are comparatively analyzed. The difference in near-field patterns of the unshielded and shielded SiPs may incur overestimation of the SE by using maximum field values. Both simulation and measurement results manifest that the gap between SiP and printed circuit board (PCB) will significantly change the radiation pattern of a shielded SiP, and thus has a great impact on the SE, especially when the frequency is above 1 GHz. However, a good correlation is found between the SE based on average near-field and the SE derived from the radiated power. This study has revealed the near-field shielding properties of SiP, which is helpful for building and analyzing the correlation among the SEs measured by different methods, including the near-field scanning, transverse electromagnetic (TEM) cell and reverberation chamber. [ABSTRACT FROM AUTHOR]

The conventional definition of shielding effectiveness (SE) is well suited for calculations of far-field electromagnetic shielding. However, in the near field, SE calculations are not as straightforward. In radio-frequency interference (RFI) problems, the majority of field coupling occurs in the near field. Thus, a well-defined method for calculating the near-field SE is needed to estimate the suppression of RFI achieved by shielding cans. In this study, a method based on near-field scanning is developed to extract the SE of board-level shielding cans. The SE is defined by modeling the shielded noise source as equivalent dipole moments. The accuracy of the equivalent source is analyzed via the least-square error and correlation coefficient as confidence verification parameters. By applying the reciprocity theorem, the voltage coupled on a planar inverted F antenna from an unshielded and a shielded source is calculated. The coupled voltage from a shielded noise source serves as a reference to validate the effectiveness of the proposed method. Practical shielding cans were used to develop and validate the SE extraction method using full-wave 3D simulations and measurements. [ABSTRACT FROM AUTHOR]

In this article, an ultrawideband magnetic probe with high electric field suppression ratio (EFSR) is proposed. The probe has three parts: the loop part, the transmission part, and the head part. Shield metal sheets are designed in the loop part to enhance EFSR. The tapered transmission line in the transmission part and the quasi coaxial transition in the head part are adopted for impedance matching between the induction loop and the grounded coplanar waveguide (GCPW) in the head part. Then, segmented resistance–inductance–capacitance (RLC) equivalent circuit models of the probe are proposed for magnetic field coupling and electric field coupling, which are suitable for accurate modeling and efficient optimization of the magnetic probe. In addition, the coupling capacitors between the shield metal sheets and the device under test (DUT) are extracted utilizing the conformal transforming method with analytical formulas. Finally, this magnetic probe is fabricated under printed circuit board (PCB) technology and used in measuring the magnetic field distribution. The measurement and simulation results agree well. The probe has a bandwidth of 100 MHz–30 GHz and an EFSR of higher than 21 dB. Compared with the conventional probe with similar bandwidth, the proposed probe can improve the EFSR by 9 dB. [ABSTRACT FROM AUTHOR]

System-level electrostatic discharge (ESD) noise due to electromagnetic fields radiating from an ESD generator were measured and analyzed in a solid-state drive (SSD) storage system. The field sources of an ESD generator were efficiently modeled from the measured tangential magnetic fields in front of a ESD generator. The extracted field sources were incorporated into a full-wave solver, and the fields inside the disk-array enclosure (DAE) were simulated and validated by comparing to measured fields. The field source models of the ESD generator were then also utilized to predict transient ESD-induced noise voltages in a simplified SSD. Finally, the coupling mechanism and the effects of the DAE geometry were investigated. [ABSTRACT FROM AUTHOR]

This article proposes and analyzes two possible methods to compensate the raw near-field data obtained with an array of near-field probes. The first method is based on the spatial compensation procedure for a single probe and is modified toward an array of probes. The second method is to use standard spectral (plane wave) single-probe compensation. To use the latter, guidelines on how to design an array and modify the overall measurement procedure such that mutual coupling and edge effects have less influence are given. The different methods are tested in simulation and compared with the performance of compensation on a single probe. It is shown that the standard spectral single-probe compensation, in combination with proper array design, will result in an error as low as the same compensation technique used on a single probe. It is also shown that the spatial compensation improves the results in comparison with regular calibration. However, the error is not low enough to be used for postprocessing due to ill-conditioning. This article shows the path to much needed, fast, and accurate near-field measurements. [ABSTRACT FROM AUTHOR]

Methods for measuring the bistatic RCS of objects using near-field scanning and near-field to far-field transformation by mathematical modeling are analyzed. A model two-dimensional problem of diffraction by extended scatterers is considered. A cylindrical scanner is used. One important issue in this case is the possibility of scanning on a truncated surface rather than on the full scanning surface in order to reduce the cost of measurements. Under such conditions the results of the classical method become poorly predictable and an adapted method is required. Two methods based on the expansion in cylindrical waves when scanning on a truncated surface are compared: the classical one, used to measure antenna radiation patterns (the field outside the scanning area is assumed to be zero) [1] and the method proposed by Kim, which allows one to strictly take the truncation of the scanning surface by angle into account [2]. Comparison of the obtained results of both methods confirms the prospects of using the second method. [ABSTRACT FROM AUTHOR]

In this article, we present an efficient phaseless inverse source method (PISM) to reconstruct equivalent sources on a printed circuit board (PCB) using magnitude-only single-plane near-field scanning. The equivalent source distribution reconstructed by the conventional source reconstruction method requires accurate near-field magnitude and phase information, but phase measurement is difficult in many cases due to inaccuracy and complexity. In order to describe the inverse problem between phaseless fields and radiation sources, a nonlinear cost function based on surface integral equations is established. The cost function of the PISM is rapidly minimized by an iterative optimization and regularization technique for nonlinear ill-posed systems. The proposed method gives the characterization of PCBs both for diagnostic tasks of radiation sources and the near-field radiation behavior prediction when the phase information is missing. It also shows excellent robustness in tackling with various near-field data and noises. Both numerical examples and laboratory experiments are given to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This proposal is devoted to a collaborative approach dealing with microwave microscopy experiments. The application is dedicated to an electromagnetic field cartography above circuits and the influence of nanometric material layer deposition on the circuits. The first application is associated to a microstrip ring resonator. The results match with the simulated fields. The second application is focused on the effects of a dielectric layer deposited on the circuit and its impact in terms of electromagnetic propagation.

Electromagnetic patterns in near field scanning usually give important information about the source inside an device under test. In this paper, we develop a postprocessing technique, including standard-deviation-based method, principal component analysis, and K-means method, so that the electromagnetic patterns in near field scanning can be extracted fast and grouped automatically and efficiently. The postprocessing techniques are applied to experimental near-field scanning of ICs, such as a microcontroller unit (MCU) and a field programmable gate array (FPGA). The grouping on the electromagnetic patterns of the MCU is in good agreement with the published grouping result, and the grouping on the electromagnetic patterns of the FPGA can find out the additional cluster responsible for additional circuit. [ABSTRACT FROM AUTHOR]

In this paper, an electromagnetic probe is proposed for the near-field scanning. Its detection section is made of a miniature loop-wire hybrid structure, which can measure ${H} _{x}$ , ${H} _{y}$ , and ${E} _{\textit {z}}$ simultaneously. It is optimized to achieve a wide working band from 0.1 to 15 GHz. The calibration and measurement error of the probe are discussed in detail. The probe is fabricated as a four-layer printed circuit board (PCB) with the RO4350B dielectric. A near-field scanning system with the manufactured probe is set up to test the near fields above a Z-type microstrip line and an inverted-F antenna. By comparing the measurement and simulation results, the accuracy of the proposed multi-component probe is verified. It greatly improves the near-field scanning efficiency compared to the traditional single-component probe. [ABSTRACT FROM AUTHOR]

In this paper, a simple and accurate equivalent circuit of the magnetic probe is proposed. Based on the equivalent circuit, a high-frequency probe for near-field measurements is proposed, manufactured, and tested. To increase its working frequency, its parasitic inductance and capacitance are reduced by using a small loop aperture and a tapered transition. The working frequency of the probe is up to 30 GHz. At the same time, sidewall metallization and bottom-vias are used in the probe, which result in a good performance of electric field suppression. The transmission section of the probe is optimized at high frequencies by using via fence and coax-thru-hole vias. The magnetic field probe is built on a four-layered printed circuit board with Rogers substrate. The loop aperture size of the probe is $250\,\,\mu \text{m}\,\,\times 250\,\,\mu \text{m}$ , so it has a high spatial resolution and is helpful to measure the detailed magnetic field from a small device. The probe is calibrated by a standard coplanar waveguide with a backside ground (CPWG). Finally, a near-field scanning system with the fabricated probe is set up to test the magnetic field above an unknown CPWG and microstrip line. From the near-field scanning results, it can be concluded that the probe can accurately measure the magnetic field over a wide frequency band. [ABSTRACT FROM AUTHOR]

A microwave ultrawideband (UWB) radar system is developed and used for non-destructive testing (NDT) of multilayered structures. The effectiveness of this approach lies in the choice of critical parameters such as waveform type, operational frequency range, and stand-off distance. Matched filtering of the received waveform with a replica of the transmitted signal is used to locate hidden anomalies or flaws within a multilayered structure, most of which are not apparent through common visual-inspection techniques. Due to the impulse-like autocorrelation properties of white noise, noise waveforms provide the ability to locate material discontinuities as well as, or better than, other common waveforms such as Gaussian-modulated sinusoidal pulses (GMSP) or linearly frequency modulated chirp signals. Experimental data are gathered using a specially developed microwave imaging system which operates in the X-band frequency range. Subsequently, two-dimensional (2-D) and three-dimensional (3-D) images are rendered following a raster scanning approach to reveal internal boundaries, hidden inclusions, and defects due to impact damages or corrosion in fiber-reinforced polymer (FRP) materials and other dielectric materials. [ABSTRACT FROM AUTHOR]

A new equivalent dipole model hybrid with artificial neural network (ANN) is proposed in this paper for electromagnetic interference (EMI) estimation. Equivalent dipole method, based on the free-space Green’s function, is usually used to model unknown EMI sources on printed circuit boards. For high-speed and dense circuits, there may be multi-reflection and/or diffraction between the EMI source and its nearby components. Traditional dipole model usually omits such effects and leads to an inaccurate result in some cases. In our proposed method, the Green’s function of dipole is taken as input and the radiated EMI field is taken as the output of ANN. We use the powerful mapping ability of ANN to modify the matrix–vector multiplication between free-space Green’s function and dipole moments in the traditional dipole model, so that a new mapping between equivalent dipoles and their radiated fields is established. The near field of the EMI source is obtained by planar scanning, and is used for ANN training. After training, the ANN is used to predict the EMI field at the region of interest. Both numerical example and measurement example are given to show the effectiveness of the proposed ANN method. This paper provides a novel source reconstruction solution for the EMI problems. [ABSTRACT FROM AUTHOR]

A near-field scanning is usually time-consuming to map the electromagnetic field along the surface of a device. In this communication, a dual probe is proposed with a U-shaped loop to sense radio frequency (RF) magnetic and electric fields simultaneously, so that the one-time scanning by the dual probe can replace the two-time scanning by single-detector probes. Different from the traditional near-field scanning by using a single-detector probe and spectrum analyzer, the proposed scanning can be achieved by the two-output probe and a two-port vector network analyzer connecting to the probe. The efficient near-field scanning measurements of the electric and magnetic field on a conductor-backed coplanar waveguide transmission line and an RF power divider by using the dual probe are in agreement with those by using two single-detector probes. [ABSTRACT FROM AUTHOR]

In near-field scanning, the model parameters for the antenna under test can be determined from measured probe outputs by solving a linear system of equations in the least-squares sense. The model parameters are far-field pattern values, cylindrical or spherical-wave expansion coefficients, or equivalent surface-source values. The normal matrix of this linear system of equations is sometimes extremely ill-conditioned. This occurs when certain sets of model parameters lie outside the spatial bandwidth of the operator that computes the probe output. One remedy is to restrict the sets of model parameters allowed and perform upsampling if needed to achieve the desired accuracy. These ideas are illustrated through analysis and examples that involve both 2-D and 3-D scanning geometries. [ABSTRACT FROM AUTHOR]

In this paper, a method is proposed to calibrate a probe by placing it into a known field and referencing its output voltage to the known field. A transmission line is a convenient structure for creating such a known field. This paper presents the effect of the inhomogeneous medium on the near-field generated over a grounded coplanar waveguide (GCPW) printed circuit board (PCB) and reports the field pattern over the GCPW. GCPW PCBs are used to determine the probe factor for near-field scanning applications. A near-field scan is performed to visualize the near-field sources over a device under test (DUT). The near-field is measured by using E- and H-field electromagnetic interference probes. The output of these probes is a voltage and using the probe factor, the field present over the DUT can be determined. To calculate the probe factor, the near-field strength needs to be known using the 3-D simulation. GCPW creates a quasi-TEM field. The effect of non-TEM modes is easily underestimated, such that non-TEM fields prevent the user from determining the unwanted field suppression of probes at higher frequencies. [ABSTRACT FROM AUTHOR]

This paper presents a detailed treatment of modeling of noisy electromagnetic field propagation as well as a formulation for its numerical implementation along with numerical and experimental examples. Modern electromagnetic interference measurement systems operate in time domain (TD) and exhibit gigahertz bandwidths together with short measurement times. Two-point near-field scanning with two field probes allows recording of near-field autocorrelation and cross correlation data as a basis for the TD simulation of noisy electromagnetic (EM) field propagation, also in complex environments. TD modeling yields results for the whole frequency band under consideration with a single computational run and is advantageous if results for a broad frequency range are of interest. We introduce a correlation dyadic-based approach for noisy EM field modeling using analytic TD Green’s functions. For experimental validation of the method, we have computed spatial cross correlations in the far field from experimental near-field scanning data of a digital circuit board under test. The propagated results are compared to cross correlations obtained from measurements performed directly in the far field. [ABSTRACT FROM AUTHOR]

Electromagnetic interference (EMI) source reconstruction typically requires accurate measurements of both near-field magnitude and phase information. In some cases, an accurate phase measurement may not be practically feasible. A phase-retrieval method based on phaseless and single-plane near-field scanning is presented in this paper. By using an interpolation technique, the original data of field magnitude used for reconstruction can be divided into two groups: the sampling and interpolation groups. Subsequently, iteration algorithm together with the singular value decomposition method is employed to reconstruct the equivalent dipole model of the EMI source. Both numerical example and measurement example are given to verify the effectiveness of the proposed algorithm. The major advantage of the proposed method is that it can save a half scanning time and still produces a valid EMI source model. It also shows an ability to reduce some measurement errors. [ABSTRACT FROM PUBLISHER]

In this letter, near-field scanning technology is utilized to analyze the shielding effectiveness (SE) of the system-in-package (SiP) module at the frequency of 1–6 GHz. Different definitions of the near-field SE are explored and analyzed. The SE is defined by using values of the radiated magnetic near-field from the SiP module, including the maximum value, the spatial averaged value, and the value at the same observation point, respectively. The SE defined by the spatial averaged value is a reasonable method to represent the overall SE of a well-shielded SiP module especially at low frequencies. Besides, a comparison of the SE between the reverberation chamber measurement and averaged magnetic near field is carried on. Good consistency is obtained, which confirms the reliability and efficiency of the near-field scanning method. [ABSTRACT FROM AUTHOR]

Time-domain near-field scanning is gaining more and more interest within EMC engineering to analyze electromagnetic near-fields of, e.g., quasi-stationar devices. When using a digital oscilloscope to scan the near-fields of an electronic device, the oscilloscope measures time-domain signals that comprise in most cases a large number of frequency components. For many of these components, noncoherent sampling occurs, resulting in spectral leakage when calculating the frequency spectrum of the time-domain signals with the discrete Fourier transform. This paper proposes an improved method to detect the presence of such noncoherently sampled signals as well as an iterative algorithm to obtain accurate approximations of all the frequency components with their accompanying amplitudes and phase angles. The algorithm excels over existing algorithms in obtaining these values especially in situations where several sinusoidal components are close to each other in the spectrum. This is achieved, thanks to an iterative process of removing the influence of the multiple sinusoidal components on each other. This paper contains the mathematical description of the algorithm and a numerical example evaluating the accuracy of the algorithm. The algorithm has a higher accuracy than the existing approaches, e.g., multipoint Interpolated Discrete Fourier Transform (IpDFTs), with only a slight increase of the computational cost. [ABSTRACT FROM AUTHOR]

Near-field coupling in mixed digital/RF circuit design is critical to system sensitivity for modern high speed electronic systems. This paper presents radiation noise source modeling methods and applies equivalent noise source models to near-field coupling estimations. The noise source can be either modeled by physics-based dipole moment model or Huygens's equivalent model with data obtained from near-field scanning. The fundamental principles of both methods are first studied by simulation. A clock buffer integrated circuit is first modeled as a dipole moment model. The tangential fields on Huygens's box can be calculated by a dipole moment model with negligible multiple scattering effect assumption. The noise coupling then can be obtained by surface integration of Poynting vector at the RF antenna receiving port by full-wave simulation. [ABSTRACT FROM AUTHOR]

For large, complex systems with multiple sources at the same frequency, localizing the sources of radiation often proves difficult. This paper presents an emission source microscopy (ESM) technique derived from synthetic aperture radar (SAR) to localize radiating sources on a PCB. Near-field scanning provides limited information about the components contributing to far-field radiation. This paper presents the source localization methodology, supported by simulation and measurement results. After localizing the sources, the far-field contribution and the total radiated power from each individual source can be estimated. The results show that the proposed method can distinguish between multiple radiating sources on a complex PCB. [ABSTRACT FROM AUTHOR]

This paper describes the application of a new and easy to implement algorithm to EMI near-field scanning measurement results obtained with a time-domain-based measurement system. The algorithm aims to reduce the effect of spectral leakage on amplitude and phase of the measured field components. The proposed algorithm significantly increases the accuracy of the measured electromagnetic near field with a limited extra computational cost. The versatility and effectiveness of the proposed algorithm is shown on both simulated and measured data. It is shown that for situations with one single frequency component or with several well-separated frequency components, the algorithm is as performant as the application of a flat top window and outperforms other types of windows. However, as soon as the frequency components approach each other implying their spectral leakage patterns overlap, the proposed algorithm outperforms the application of a flat top window. [ABSTRACT FROM AUTHOR]

In this paper, an approach is proposed to predict the maximum far-field radiated emission based on phaseless near-field scanning. The maximum radiated emission from printed circuit boards is assumed to be produced by dominant magnetic dipoles located by the near-field measurement. The particle swarm optimization technique is then employed to identify the complex moment components of the dipoles. Once the dominant dipoles at each emission frequency are determined, the maximum far-field radiated emission in the interested frequency range can be calculated using the method of moments. The proposed approach allows a quick assessment of far-field radiated emission precompliance in a wide frequency range by near-field scanning. Experimental results are presented to show its feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

For radiation source locating above a ground plane, its far field can be predicted by only the magnetic near field through the method proposed in this paper. This method applies the finite element method to get the equivalent current sources from the tangential magnetic near fields. With the equivalent current sources, the far-field radiation can be calculated based on Huygens's principle and image theory. The magnetic near field is scanned on a Huygens's surface that encloses the source with its ground. In this paper, this Huygens's surface was first proposed as a five-surface cube on the ground. Then, the Huygens's surface was further simplified by using four lines instead of four side walls to make the proposed method easier in regards to practical near-field scanning. Several numerical examples were tested to validate the proposed method. In addition, the proposed method was validated experimentally by using a patch antenna. The performance of using only the top plane near fields was also investigated and discussed. By using only the magnetic near fields on the simplified Huygens's surface, the proposed method significantly saves measurement time and cost while also retaining good far-field prediction. [ABSTRACT FROM AUTHOR]

In this paper, an efficient method for the numerical simulation of near- and far-field propagation of stochastic electromagnetic (EM) fields is presented. The method is based on the transformation of field correlation dyadics using Green's functions or the field transfer functions computed for deterministic fields. The method accounts for arbitrary correlations between the noise radiation sources and allows to compute the spatial distribution of the spectral energy density of noisy electromagnetic sources. The introduced methodology can be combined with available electromagnetic modeling tools. It is shown that the method of moments can be applied to solve noisy electromagnetic field problems by network methods applying correlation matrix techniques. Examples demonstrating the strong influence of the correlation between the sources on the spatial distribution of the radiated noise field are presented. [ABSTRACT FROM PUBLISHER]

Near-field scanning can be used to determine the far-field emissions of electronic devices. In general, this requires phase-resolved electric and magnetic near-field data. To capture a broad frequency range relatively quickly, a multichannel oscilloscope can be used for data capture. The phase relationship of the fields between different space points and between the electric and the magnetic field needs to be known. Consequently, it is required to determine the complex-valued probe factor (PF) of the probe, cable, and amplifier chain. This paper presents a fast and efficient calibration method which uses the same setup and instruments during calibration and measurement, and it allows for easy and economical integration of the calibration hardware and software into the scanning system. Known fields are created by a microstrip trace driven with a comb generator. By referencing measured data to this known field, the PF is obtained over a broad frequency range by capturing one time-domain waveform. [ABSTRACT FROM PUBLISHER]

Electromagnetic field coupling and radiation from a heat sink is a challenging issue in the electromagnetic compatibility design of high-speed circuits. In order to accurately predict the fields excited by a heat sink, an approach is proposed in this paper to include the equivalent excitation of the heat sink, which is described by some dipole moments constructed from the near-field scanning of the integrated circuit beneath the heat sink. With both the dipole moments and the passive heat-sink structure incorporated in a full-wave model, near-field coupling and far-field radiation can be estimated, and the heat-sink structure can be optimized for mitigating unintentional interferences. Two examples are used to validate and demonstrate the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, an improved dipole-moment model for characterizing near-field coupling and far-field radiation from an IC based on near-field scanning is proposed. An array of electric and magnetic dipole moments is used to reproduce the field distributions in a scanning plane above an IC. These dipole moments can then be used as noise sources for the IC. In order to ensure the accurate prediction of the near-field coupling from the IC, the regularization technique and the truncated singular-value decomposition method are investigated in this paper, together with the conventional least-squares method, to reconstruct the dipole moments from the near-field scanning data. A simple example is used to demonstrate the approach. The improved dipole-moment model is particularly useful for addressing radio-frequency interference issues where near-field noise coupling needs to be accurately analyzed. [ABSTRACT FROM AUTHOR]

We discuss the error that results when the far field is reconstructed from spatially truncated near-field samples and present an effective mitigation technique based on the Slepian sequence for acoustic spherical near-field scanning. We show that the truncation error is inevitable whenever the far field is reconstructed using the classical near-field-to-far-field transformation. After discussing the Slepian sequence for a truncated spherical surface and its analytic and numerical properties, we apply it to expand truncated NF samples and derive the near-field-to-far-field transformation of the resulting expansion coefficients, from which the far field can be computed. We demonstrate the efficacy of this transformation by applying it to near-field scanning for bistatic scattering from a sphere and radiation from a current distribution. [ABSTRACT FROM AUTHOR]

We introduce a near-field to far-field transformation for two-dimensional cylindrical/spherical scanning that significantly reduces angular-truncation errors. After examining the limitations of the traditional multipole-based expansion of truncated scan data, we consider an alternative expansion based on Slepian functions and show how far-field values can be extracted from the resulting expansion coefficients. We compare the performance and computational cost of the new transformation with those of the traditional one. [ABSTRACT FROM AUTHOR]

In this paper, a method for representing electromagnetic emissions from a printed circuit board (PCB) using an equivalent dipole model deduced from near-field scanning is proposed. The basic idea is to replace the PCB with a set of infinitesimal dipoles that generate the same radiated fields. Parameters of the equivalent dipoles are determined by directly fitting to the measured magnetic near fields. In closed-environment simulations, the equivalent method is extended to a dipole-dielectric conducting plane model to account for the interactions between the PCB and enclosure by including the basic physical features of the PCB. The electromagnetic emissions can then be predicted by solving the equivalent model with numerical methods, thereby, significantly reducing the simulation time and storage costs. A basic test board and a more complex practical telemetry PCB are modeled in different configurations and compared with measurements and full-field simulations, confirming the validity and efficiency of the model. [ABSTRACT FROM AUTHOR]

This paper presents an electromagnetic noise source approximation method based on a 2-D array of electric dipoles for use in finite-difference time-domain simulations. The currents (both magnitude and phase) of these dipoles are optimized via a particle swarm algorithm so as to minimize the difference between the magnetic near-field produced by the dipole array and the magnetic near-field produced by the device under test. The method presented requires only the magnitude of the magnetic field to be measured, simplifying the measurement process. The new noise source modeling method has been applied to a transmission-line test case, demonstrating the performance and accuracy of the method. [ABSTRACT FROM AUTHOR]

The paper presents an original methodology to characterize electromagnetic disturbances radiated from power electronic devices. The approach is based on the substitution of an equivalent set of elemental dipoles for the real system; this set radiates the same near-field. The dipoles are determined from a near-field cartography of the fields obtained with a measurement bench. The parameters of the dipoles are determined by solving an inverse problem. The efficiency of the approach is demonstrated for a 3-D case and for a practical dc-dc converter. [ABSTRACT FROM AUTHOR]

Abstract: A transformation linking spherical multipole fields with generalized spheroidal multipole fields is derived. Applications including the inverse diffraction problem for spherically scanned near-field data for sources that due to conformal considerations are efficiently described using spheroidal (either oblate or prolate) volume support regions are discussed with the aid of numerical illustrations. [Copyright &y& Elsevier]

A theory is presented for computing scattered far fields of targets from cylindrical near-field measurements. The targets are illuminated by plane waves and measured in a radio anechoic chamber on a cylindrical scan surface. The scattered field on the scan cylinder is obtained by background subtraction. The near-field data is truncated at the top, bottom, and angular edges of the scan cylinder. These truncation edges can cause inaccuracies in the computed far fields. Correction techniques are developed for the top and bottom truncation edges. The cylindrical wave expansions automatically apply angular tapers to the near-field data that reduce the effect of the angular truncation edges. The taper functions depend on the angular sample spacing and are related to the currents induced on perfectly electrically conducting PEC cylinders in related scattering problems. The method of stationary phase is employed with asymptotic expressions for the taper functions to determine the area on the scan cylinder that is most important for computing the far field in a given direction. The theory is validated through numerical examples involving electrically large scatterers. The edge-correction techniques significantly increase the accuracy of the computed far field. A companion paper presents experimental results. [ABSTRACT FROM AUTHOR]

A procedure for the calibration and compensation of near-field scanning is described and demonstrated. Ultimately, the objective is to quantify the individual field components associated with electromagnetic interference (EMI) from high speed circuitry and devices. Specific examples of these methods are shown. The effects of compensation are small but noticeable when the uncompensated output signal from near field scanning is already a very good representation of the field being measured. In other cases, the improvement provided by compensation can be significant when the uncompensated output signal bears little resemblance to the underlying field. [ABSTRACT FROM AUTHOR]