Canonical and Quasi-Canonical Probability Models of Class a Interference

The earlier work of the author on Class A electromagnetic interference (EMI) (RF noise) models is further developed and extended to include "approximately canonical" and "quasi-canonical" cases, in addition to the earlier strictly canonical forms. Along with a general development of the first-order probability models of Class A noise here, which now include both scenario-implicit and scenario-explicit formulations, the following new and general results are obtained: 1) the demonstration that the Rayleigh pdf of received envelopes is the necessary and sufficient condition for the strictly canonical Class A model; 2) use of the EMI scenario in calculating the parameters of the model; 3) methods and conditions for determining approximately canonical cases; 4) specific exact characteristic functions (CF), pdf's, and APD's for some basic single-random-source scenarios; 5) general quasi-canonical forms and specific examples, showing acceptable agreement with corresponding results for closely related EMI scenarios determined by simulation; as well as 6) a general formulation of EMI first-order statistics for arbitrary (including small) numbers of potentially interfering sources. Another principal overill result is extended qualitative and quantitative insights into the Class A EMI model as a whole. Many special results are included, in addition.     

Multiple targets characterization of electromagnetic vulnerability

We use statistical selection methodology to characterize multiple targets in electromagnetic fields, which result from ground, weather, and sea clutter or internal electromagnetic interference due to the antenna subsystems. This electromagnetic interference occurs at the same frequencies as the target returns yet a specific statistical distribution in amplitude emerges over time. Holland and St. John [Statistical electromagnetics, Technical Report AFRL-DE-PS-TR-1998-1025, Air Force Research Laboratory, Direct Energy Directorate, Air Force Material Command, Kirtland Air Force Base, 1988] concluded that the observed EM field power fluxes and cable powers follow either a chi-square distribution or a log-normal distribution, which implies either distribution in all measurements due to internal electromagnetic interference (EMI) problems. That is such an EM field can be characterized by either an exponential distribution or a log-normal distribution. These cases exist also in a far field as a result of what the aircraft returns, while the distribution exists due to multiple reflecting surfaces instead of internal EM fields from radar subsystems previously mentioned. Clutter also produces these same distributions in the far field. For the exponential distribution case, we propose subset selection procedure to identify EM fields whose reference parameters are those of candidate targets rather than the interfering EM sources. We discuss the properties of our proposed procedure by numerical examples and give simulation examples to illustrate the procedure.     

多层介质中谱域格林函数的解析公式及在微带天线中的应用

首先假定平面电流源位于任一层介质中，然后利用谱域法和波矩阵技术，通过求解矢量电波场动方程，推导出了多层介质中谱域格林函数的解析公式，将所得公式应用于多层介质微带 天线的分析中，得 到了天线辐射场的理论计算公式，分析计算了一些工程实例，实验结果证实了理论计算的正确性。     

Time-domain study of half-space transmission problem with verticaland horizontal dipoles

The paper deals with the transient fields transmitted through the interface between the air and ground. Excitation for the electromagnetic fields is produced by a vertically or horizontally oriented impulsive dipole, which may be electric or magnetic. However, only electric sources are discussed, because the analog results for magnetic sources are obtained easily through the duality transform. The ground medium has arbitrary permittivity and permeability, but it is restricted to lossless, i.e. the conductivity is assumed to be zero. In this study simple integral expressions are derived for the time-dependent Hertz vector in the ground from which the propagating transient fields can be obtained through differentiation. In certain specific cases some components of electric or magnetic field have a closed-form solution in terms of elementary functions. All the nontrivial solutions of this type in the ground medium are given     

A Novel Approach for Target Detection and Classification Using Canonical Correlation Analysis

We present a novel detection approach, detection with canonical correlation (DCC), for target detection without prior information on the interference. We use the maximum canonical correlations between the target set and the observation data set as the detection statistic, and the coefficients of the canonical vector are used to determine the indices of components from a given target library, thus enabling both detection and classification of the target components that might be present in the mixture. We derive an approximate distribution of the maximum canonical correlation when targets are present. For applications where the contributions of components are non-negative, non-negativity constraints are incorporated into the canonical correlation analysis framework and a recursive algorithm is derived to obtain the solution. We demonstrate the effectiveness of DCC and its nonnegative variant by applying them on detection of surface-deposited chemical agents in Raman spectroscopy.     

高速PCB近区场电磁骚扰研究

分析了高速电子电路产生的电磁干扰(EMI)及相关印刷电路板(PCB)上电磁骚扰源的模型特征。利用电偶极子与磁偶极子模型分别对PCB上的共模辐射源和差模辐射源建模,着重探讨近区场辐射特征。以一种500MHz的高速电路为例,在MATLAB平台上分别对其电场与磁场进行仿真。结果表明,其近区场电场与磁场强度最高分别可达5×1011μV/m和9×1011μA/m。依据所使用模型及其仿真结果,有针对性地提出几种降低高速PCB电磁骚扰的方案,并比较了这几种方案的优劣。     

Electromagnetic interference (EMI) of system-on-package (SOP)

Electromagnetic interference (EMI) issues are expected to be crucial for next-generation system-on-package (SOP) integrated high-performance digital LSIs and for radio frequency (RF) and analog circuits. Ordinarily in SOPs, high-performance digital LSIs are sources of EMI, while RF and analog circuits are affected by EMI (victims). This paper describes the following aspects of EMI in SOPs: 1) die/package-level EMI; 2) substrate-level EMI; 3) electromagnetic modeling and simulation; and 4) near electromagnetic field measurement. First, LSI designs are discussed with regard to radiated emission. The signal-return path loop and switching current in the power/ground line are inherent sources of EMI. The EMI of substrate, which work as coupling paths or unwanted antennas, is described. Maintaining the return current path is an important aspect of substrate design for suppressing EMI and for maintaining signal integrity (SI). In addition, isolating and suppressing the resonance of the DC power bus in a substrate is another important design aspect for EMI and for power integrity (PI). Various electromagnetic simulation methodologies are introduced as indispensable design tools for achieving high-performance SOPs without EMI problems. Measurement techniques for near electric and magnetic fields are explained, as they are necessary to confirm the appropriateness of designs and to investigate the causes of EMI problems. This paper is expected to be useful in the design and development of SOPs that take EMI into consideration.     

Decomposition of electromagnetic boundary conditions at planarinterfaces with applications to TE and TM field solutions

Electromagnetic fields in homogeneous source-free regions can be decomposed into fields that are TE and TM with respect to a particular reference direction (e.g., the z direction). If transverse sources exist, both TE and TM fields may be excited simultaneously. This paper considers the case of two infinite regions having a common planar interface and prescribed sources (surface currents) on the interface. The source currents are decomposed in a manner consistent with the decomposition of the fields. Accordingly, a procedure is established for describing the boundary conditions at the interface in terms of the longitudinal field components E_z, H_z and the surface currents J¯_s. The development is unique in that the continuity of the transverse field components at the boundary are not explicitly considered but interpreted in terms of z-directed fields. This boundary condition approach is shown to give results consistent with those obtained by matching the tangential fields at the interface using vector transforms. A simple example illustrating the procedure using a ring of current in free-space is presented     

EMI characteristics of distribution lines located in desert lands

Results are reported of a two-year field study carried out to determine the electromagnetic interference (EMI) characteristics of distribution lines located in a hot, dry desert environment with high amounts of airborne particulates. Typical characteristics such as EMI frequency spectrum, EMI lateral profile, and statistical scatter in EMI levels were investigated. The results show that unlike distribution lines located in wet climates, the lines located in dry, desert regions do not generate appreciable levels of radio interference (RI). Details are provided about the lines, environment conditions, measurement procedures, and EMI characteristics. The results of the field study have been verified in the laboratory by determining the characteristics of typical EMI sources that can occur on distribution lines     

The radiation operator

The concept of the radiation operator is introduced to assist in the analysis of various problems involving sources and their radiation fields. It gives the field outside the source region as operating on the field of a point source. Because there is a simple connection between the radiation vector describing the far-field and the radiation operator, it can be used to define fields anywhere outside the source region from their values in the far-field zone. Another important properly of the radiation operator is its ability to express sources of fields given their radiation pattern and polarization in the far zone. The source of such a field can be written in the form of radiation operator operating on a current element, the delta function source. To interpret this in terms of computable functions, existing tables of operational rules for different classes of operators can be applied. Examples of radiation operators corresponding to different sources are given together with examples of sources corresponding to given radiation field patterns. Finally it is shown that the radiation operator allows a considerable simplification to the derivation of the multipole expansion theory when compared to the classical recursion-formula derivation through spherical harmonic eigenfunctions     

The human vector magnetogastrogram and magnetoenterogram

Electrical activity in the gastrointestinal system produces magnetic fields that may be measured with superconducting quantum interference device magnetometers. Although typical magnetometers have detection coils that measure a single component of the magnetic field, gastric and intestinal magnetic fields are vector quantities. We recorded gastric and intestinal magnetic fields from nine abdominal sections in nine normal human volunteers using a vector magnetometer that measures all three Cartesian components of the magnetic field vector. A vector projection technique was utilized to separate the magnetic field vectors corresponding to gastric and intestinal activity. The gastric magnetic field vector was oriented in a cephalad direction, consistent with previously observed data, and displayed oscillatory characteristics of gastric electrical activity (f = 3.03 +/- 0.18 cycles/min). Although the small bowel magnetic field vector showed no consistent orientation, the characteristic frequency gradient of the small bowel electrical activity was observed. Gastric and intestinal magnetic field vectors were oriented in different directions and were thus distinguished by the vector projection technique. The observed difference in direction of gastric and intestinal magnetic field vectors indicates that vector recordings dramatically increase the ability to separate physiological signal components from nonphysiological components and to distinguish between different physiological components.     

Analysis of an infinite current source above a semi-infinite lossyground using fictitious current auxiliary sources in conjunction withcomplex image theory techniques

The canonical problem of an infinitely long electric current line radiating above a lossy infinite half space is examined. The solution is based on the method of auxiliary sources (MAS). In this method one can, in general, apply a numerical solution by introducing sets of fictitious current sources whose fields are elementary analytical solutions to the boundary value problem, in order to approximately describe the actual electromagnetic (EM) fields in each domain. In general, the convergence rate and the accuracy of the MAS solution depend on the spatial distributions of the fictitious current sources sets and their locations in regard to the singularities of the actual EM field simulated by each set. Here, both the accuracy and the convergence rate of the method are examined, investigating complex image approximations in order to optimally choose the auxiliary sources placements. It is proved that the convergence rate and the accuracy of the method are significantly improved by utilizing the complex images as locations of the auxiliary sources. The main contribution of the paper consists in the application of MAS to an open structure, which involves lossy dielectrics excited by a nonuniform EM field, as well as in the optimal choice of the locations of the fictitious current sources according to complex image techniques     

Nodal-based finite-element modeling of Maxwell's equations

Weak forms are derived for Maxwell's equations which are suitable for implementation on conventional C⁰ elements with scalar bases. The governing equations are expressed in terms of general vector and scalar potentials for the electric field intensity vector. Gauge theory is invoked to close the system and dictates the continuity requirements for the potentials at material interfaces as well as the blend of boundary conditions at exterior boundaries. Two specific gauges are presented, both of which lead to Helmholtz weak forms which are parasite-free and enjoy simple, physically meaningful boundary conditions. A general and numerically efficient procedure for enforcing the jump discontinuities on the normal components of vector fields at dielectric interfaces and boundary conditions on curved surfaces is also given     

Stretchable EMI Measurement Sheet With 8 $times$ 8 Coil Array, 2 V Organic CMOS Decoder, and 0.18$ mu$m Silicon CMOS LSIs for Electric and Magnetic Field Detection

A stretchable 12 × 12 cm² electromagnetic interference (EMI) measurement sheet is developed to enable the measurement of EMI distribution on the surface of electronic devices by wrapping the devices in the sheet. The sheet consists of an 8 × 8 coil array, a 2 V organic CMOS row decoder and a column selector, 40% stretchable interconnects with carbon nanotubes, and 0.18 ?m silicon CMOS circuits for electric and magnetic field detection. The sheet detects the total power of an electric field in the band up to 700 MHz and that of a magnetic field up to 1 GHz. The minimum detectable powers of the electric and magnetic fields are -60 and -70 dBm, respectively.     

Tomographic reconstruction of vector fields

The application of tomography to the reconstruction of vector fields is considered. Two different types of interaction between the radiation used for measurement and the investigated vector fields are discussed. A complete reconstruction of a vector field can only be obtained if measurements based on both types of interaction are available. Otherwise, only curl-free or source-free components of the field can be reconstructed. In the case of nonhomogeneous boundary conditions, additional harmonic field components occur. Some experimental results are presented showing the reconstruction of flow velocity fields based on ultrasonic time-of-flight measurements     

Cross-borehole sensing: identification and localization ofunderground tunnels in the presence of a horizontal stratification

This paper addresses the detection and localization of a buried two-dimensional (2D) dielectric object in the presence of an air-Earth interface. The techniques used are modifications of the well-known backpropagation operator, including plane-wave angular spectral filtering and detection of the cross-polarized scattered field. Cross-correlation of the received signal with a known target signature is included for comparison and found to be useful for detection. It is shown that use of the positive spatial frequency components of the fields scattered by the buried target, together with the backpropagation of vertical cross-polarized fields, yield results that are relatively insensitive to the presence of the horizontal stratification. Examples illustrate that backpropagation can be used for detection and localization purposes in a cross-borehole configuration. Some experimental results utilizing a 2.5 GHz laboratory scale model and a tunnel-like target are also included for comparison     

Theoretical and measured electric field distributions within anannular phased array: Consideration of source antennas

A detailed calculation of sources and electric fields associated with a prototype annular phased array for clinical hyperthermia is presented. Two antenna current distributions are used as field sources. One is based on a linear dipole model. The second models the thin strip antenna elements in detail, and the current is derived using the theory of a microstrip transmission line. These currents are then used to calculate the magnetic vector potential and the electric field. To verify the theoretical simulations, the magnitude of the electric field is measured under the same conditions as those used in the theoretical simulations. The comparison between measured and calculated fields demonstrates better convergence of theory and experiment when the antenna sources are modeled in detail. Thus, the use of these results for an improved incident-scatter model that will allow more general calculations of E fields in inhomogeneous media with irregular geometries is anticipated     

Coupling reduction in enclosures and cavities using electromagnetic band gap structures

The physical mechanism behind electromagnetic interference (EMI) is the coupling of energy between different primary and secondary sources of radiation and components within the package or chassis. This coupling can be either through conduction or radiation. However, regardless of the coupling mechanism, surface currents are needed to support the electromagnetic fields that eventually cause radiation, which in turn, constitute the EMI in the victim component. Minimizing these surface currents is considered a fundamental and critical step in minimizing EMI. In this work, we address novel strategies to confine surface currents. Unlike the traditional use of lossy materials and absorbers, which can be costly and can suffer from considerable disadvantages including mechanical and thermal reliability leading to limited life time, we consider the use of electromagnetic band gap (EBG) structures. These structures are inherently suited for surface current suppression. Their design is straightforward, and they are inexpensive to implement and do not suffer from the limitation of the previous methods used for the type of EMI suppression previously described. The effectiveness of the EBG as an EMI suppresser will be demonstrated using numerical simulations and measurements.     

FDTD modeling incorporating a two-port network for I/O line EMIfiltering design

Electromagnetic interference (EMI) filters are often utilized on I/O lines to reduce high-frequency noise from being conducted off the printed circuit board (PCB) and causing EMI problems. The filtering performance is often compromised at high frequencies due to parasitics associated with the filter itself, or the PCB layout and interconnects. Finite difference time domain (FDTD) modeling can be used to quantify the effect of PCB layout and interconnects, as well as filter type, on the EMI performance of I/O line filtering. FDTD modeling of a T-type and π-type filter consisting of surface-mount ferrites and capacitors is considered herein. The FDTD method is applied to model PCB layout and interconnect features, as well as the lumped element components, including the nonlinear characteristics of ferrite surface-mount parts. The EMI filters with ferrites; are included in the modeling by incorporating the time-domain Y-parameters of the two-port network into the FDTD time-marching equations. Good agreement between the FDTD modeling and S-parameter measurements supports the new FDTD algorithm for incorporating two-port networks     

Design and analysis of six port-TEM cell for generating standardelectromagnetic fields

The authors report the design and analysis of a six port-TEM cell. The cell is especially useful for EMI/EMC testing since it maximises the test area with high field uniformity in the transverse section and changes the polarisation of fields easily. The measured electric fields inside the cell agree well with the calculated results