Baum-Liu-Tesche Research Articles

Fast prediction of the shielding effectiveness of heterotypic enclosures based on EMT theory

A fast analytical method for predicting the shielding effectiveness (SE) of heterotypic enclosures was proposed. By applying the concept of electromagnetic topology, the observation points and the walls are treated as nodes, and the space between them as tubes. Equivalent circuit models of the enclosures are derived in which the aperture on the front wall are considered as a two-port network and so is the shape of the discontinuous part, which resembles a window structure. Then, the expressions of the total voltage components can be obtained using the extended Baum–Liu–Tesche (BLT) equation. Three different types of heterotypic enclosures are proposed to validate the method. Compared with numerical simulation, the proposed method can reduce the computation time from 1000 s for numerical algorithms to a few hundred milliseconds while maintaining a very close accuracy.

A model for the prediction of the shielding effectiveness of cylindrical enclosure

This paper presents a model to predict the shielding effectiveness (SE) and resonant modes of cylindrical enclosure with apertures or dielectric substrate. In this model, the Robinson equivalent circuit model (RECM) is introduced to deal with aperture impedance, and the extended form of the Baum–Liu–Tesche equation is deduced to calculate the induced voltage in the enclosure. The electromagnetic topology (EMT) model is established to analyze the process of energy transmission inside the enclosure. The energy propagation coefficient matrix and the scattering coefficient matrix are calculated to deal with the SE results of the observation point. To quantify the efficiency of the proposed model, the calculation results are compared with the full-wave transmission line matrix method (TLM) and RECM through the Fréchet distance. The comparison results show that the accuracy of the proposed model is better over a wide frequency range compared with RECM, and meanwhile, it consumes less run time and fewer CPU resources than traditional numerical methods. The validity of the presented model is verified by TLM.

An Effective Method for Fast Evaluation of Lightning-Induced Voltages on the Overhead Transmission Lines Combining Electromagnetic Topology and Matrix Pencil Method

In this article, an effective method combining electromagnetic topology (EMT) and matrix pencil method (MPM) for the fast evaluation of the lightning-induced voltages on the overhead transmission line (TL) is proposed. First, the EMT of the TL network is established based on the structure characteristic of the TL network and the scattering hypermatrix is constructed according the information of the junctions and terminal loads. Then, the piecewise sampling is performed for the spectrum of lightning signal, and the calculation of the lightning electromagnetic fields (LEMFs) of all observation points along the TL at the sampling frequency point is accomplished. Next, the supervector of the excitation source is constructed to realize the generation of the Baum–Liu–Tesche matrix equation, and the results of the lightning-induced voltages of all junctions on the TL network at the sampling frequencies are obtained. Finally, the lightning-induced voltages at all frequencies are obtained by using MPM to fit the sampled results, and the time-domain results can be generated by inverse fast Fourier transform (IFFT). In the proposed method, the LEMFs above the lossy ground are solved by the C–R formula and those below the lossy ground are calculated by the Cooray formula. Moreover, the feasibility of using EMT to analyze the lightning-induced voltages of the junctions on the TL network and adopting MPM to fit the sampled values of the lightning-induced voltages is verified. The correctness and efficiency of the proposed method are validated and proved by several numerical examples.

An improved model for the analysis of the shielding performance of an apertured enclosure based on EMT theory and BLT equation

An improved model based on the electromagnetic topology (EMT) theory and Baum-Liu-Tesche (BLT) equation is presented to evaluate the shielding performance of an apertured enclosure. First, the total aperture impedance of arbitrarily positioned apertures can be easily obtained through the coupling factor. Then, the expression of the electric field components at any monitor point inside the enclosure is derived according to the relation between voltage response and field distribution, hence, the shielding effectiveness (SE) and resonances can be analyzed conveniently. Finally, the improved model is validated by the CST, showing high efficiency and accuracy for the prediction of the SE and resonant modes of an enclosure. The improved model is suitable for handling slots that have a large length-width ratio, irregularly arranged aperture arrays, multiple apertures with different shapes and dimensions, and cascaded triple enclosures with off-centered apertures, showing the wide application range of this model.

Fast prediction of the shielding effectiveness and resonances of the heterotypic metallic enclosure with a built-in dielectric plate

On the basis of the characteristics of the heterotypic metallic enclosure with a built-in dielectric plate, this paper proposes an analytical method to evaluate the shielding performance of an apertured enclosure with convex or stepped structure under the plane wave illumination. First, the heterotypic enclosure is modeled based on the electromagnetic topology (EMT) theory, where the scattering parameter matrix at the discontinuous position can be derived according to the theory of microwave circuit. Then, the expressions of total voltage components can be obtained by using the extended Baum-Liu-Tesche (BLT) equation, which are convenient to calculate the SE at the monitor point. Finally, the effectiveness and accuracy of the proposed method in predicting the shielding effectiveness (SE) and resonances of heterotypic enclosure are verified by the computer simulation technology (CST) through several cases. Compared with the CST simulation, the proposed method is more efficient and takes up less memory.

Efficient analytical method for the shielding effectiveness of an apertured enclosure based on the BLT equation

An efficient analytical method based on the Baum–Liu–Tesche (BLT) equation has been developed for predicting the shielding effectiveness (SE) of an apertured enclosure excited by an external plane wave. First, the equivalent circuit and the signal flow graph are constructed, which helps understand the energy transmission of the enclosure. Then, the SE is obtained by using the generalised BLT equation, and the proposed analytical method is employed to analyse the effect of various parameters on the SE. Finally, the analytical method is extended to handle the enclosure with an aperture array, an enclosure with apertures at the opposing walls and two cascaded enclosures. The analytical method has been successfully verified by the CST over a wide frequency band of 0–3.0 GHz, which consumes less time than conventional numerical methods. Besides, whatever the condition of the enclosure or the aperture is, the analytical method can predict the SE and higher-order modes at higher frequencies accurately.

Propagation and Scattering Supermatrices Generation Algorithm for Implementation of Electromagnetic Topology Technique

This article proposes a method and algorithm to automatically generate the propagation supermatrix (PSM) and scattering supermatrix (SSM) from a desired topology network in order to calculate the Baum–Liu–Tesche (BLT) equation. Specific forms of the PSM, SSM, and analytical environment based on the definitions adapted by the standard electromagnetic (EM) topology (EMT) methods are proposed. The model is suitable for the EMT analysis with S-parameters and other various values for propagation and scattering situations. The EMT technique is implemented using variables and concepts such as the topology network matrix (TNM) and junction relation matrix (JRM). Additional required parameters are also defined and described. The flow of the whole algorithm and details are illustrated on a simple example for which S-parameters are calculated with the CST-MWS software. A validation of the proposed network formulation is compared to a network resolution made by the Agilent ADS circuit software.

BLT analysis method for a TWP over ground based on chain scattering parameters

This paper proposed the Baum–Liu–Tesche (BLT) method using chain scattering parameter to analyze electromagnetic coupling signals to a twisted pair over ground by HEMP. To analyze the various coupling effects between the ground and each twisted wire, Multi-conductor Transmission Line (MTL) analysis method was used. We made a TWP with many non-uniform pitch-lengths the simplified TWP-MTL model to be shown as one MTL, which reduced the calculation time and memory size when it was compared with the conventional BLT method. The results of the proposed method were compared with those of numerical analysis method and good agreements were obtained in both frequency and time domain.

Interference coupling analysis based on a hybrid method: application to a radio telescope system

Working in a way that passively receives electromagnetic radiation from a celestial body, a radio telescope can be easily disturbed by external radio frequency interference as well as electromagnetic interference generated by electric and electronic components operating at the telescope site. A quantitative analysis of these interferences must be taken into account carefully for further electromagnetic protection of the radio telescope. In this paper, based on electromagnetic topology theory, a hybrid method that combines the Baum-Liu-Tesche (BLT) equation and transfer function is proposed. In this method, the coupling path of the radio telescope is divided into strong coupling and weak coupling sub-paths, and the coupling intensity criterion is proposed by analyzing the conditions in which the BLT equation simplifies to a transfer function. According to the coupling intensity criterion, the topological model of a typical radio telescope system is established. The proposed method is used to solve the interference response of the radio telescope system by analyzing subsystems with different coupling modes separately and then integrating the responses of the subsystems as the response of the entire system. The validity of the proposed method is verified numerically. The results indicate that the proposed method, compared with the direct solving method, reduces the difficulty and improves the efficiency of interference prediction.

A Fast and Efficient Analytical Modeling Approach for External Electromagnetic Field Coupling to Transmission Lines in a Metallic Enclosure

A fast and efficient analytical approach based on the extended Baum-Liu-Tesche (BLT) equation is proposed in this paper to evaluate the external electromagnetic field coupling to transmission lines (TLs) loaded in a metallic enclosure with apertures. The scattering matrix to describe the aperture coupling characteristics required in the BLT equation is effectively derived based on the equivalent circuit theory. The analytical modeling function for calculating internal modal fields coupling to TLs is investigated and developed. Thus, the extended BLT equation can be directly employed in the assessment of current induced at the loads of TLs in the enclosure, which is illuminated by external electromagnetic fields. Via different case studies, the results calculated using the proposed analytical approach have been validated and have been in a good agreement with those simulated by numerical methods. The computational efficiency, in terms of time and memory, has also been improved much for the electromagnetic interference problems.

Electromagnetic coupling to an apertured enclosure via a penetrated transmission line based on electromagnetic topology

An efficient analytical model based on electromagnetic topology (EMT) has been developed for predicting the electromagnetic (EM) field coupling to a rectangular enclosure with an electrically large aperture via a penetrated transmission line (TL), excited by an external plane wave of oblique incidence. First, the electric field in the enclosure is calculated based on the modified Bethe’s small holes theory and mirror procedure. Then, the topology networks of the EM interaction are constructed by analyzing the coupling paths and mechanism, and the electric current induced at the termination loads of the TL is obtained using the generalized Baum–Liu–Tesche equation combined with the Agrawal’s model. The analytical model has been successfully verified by the finite difference time domain method over a wide frequency band of 0.5~3 GHz, which consumes less time than numerical methods. Finally, the analytical model is employed to analyze the effect of various parameters on the induced current, including the length, the height, and the direction of the line.

Analysis of the wireless power transfer system using electromagnetic topology method

AbstractIn this article, a new approach is proposed to analyze a wireless power transfer (WPT) system using the electromagnetic topology (EMT) method. Characteristic parameters for the junction and tube in the EMT method are obtained from the equivalent circuit of the WPT system. The load voltage is computed using the Baum–Liu–Tesche equation, which is the solver for the EMT method. A simple WPT system is analyzed to confirm the validity of the proposed method by comparing it with the conventional full wave analysis method. The analysis results obtained by the proposed method are in good agreement with the results of the conventional method.

Impact evaluation of conducted UWB transients on loads in power-line networks

Abstract. Nowadays, faced with the ever-increasing dependence on diverse electronic devices and systems, the proliferation of potential electromagnetic interference (EMI) becomes a critical threat for reliable operation. A typical issue is the electronics working reliably in power-line networks when exposed to electromagnetic environment. In this paper, we consider a conducted ultra-wideband (UWB) disturbance, as an example of intentional electromagnetic interference (IEMI) source, and perform the impact evaluation at the loads in a network. With the aid of fast Fourier transform (FFT), the UWB transient is characterized in the frequency domain. Based on a modified Baum–Liu–Tesche (BLT) method, the EMI received at the loads, with complex impedance, is computed. Through inverse FFT (IFFT), we obtain time-domain responses of the loads. To evaluate the impact on loads, we employ five common, but important quantifiers, i.e., time-domain peak, total signal energy, peak signal power, peak time rate of change and peak time integral of the pulse. Moreover, to perform a comprehensive analysis, we also investigate the effects of the attributes (capacitive, resistive, or inductive) of other loads connected to the network, the rise time and pulse width of the UWB transient, and the lengths of power lines. It is seen that, for the loads distributed in a network, the impact evaluation of IEMI should be based on the characteristics of the IEMI source, and the network features, such as load impedances, layout, and characteristics of cables.

Effect of Periodicity in Frequency Responses of Networks From Conducted EMI

In this paper, we consider different types of networks, and investigate the characteristics of the frequency responses of loads, which are distributed in the networks. Without loss of generality, both frequency-independent and frequency-dependent loads are discussed, respectively. Beginning with a transmission-line (TL) network with frequency-independent loads, via the TL theory and Baum–Liu–Tesche equation, we demonstrate that the frequency responses are periodic in the frequency domain, where the periodicity is derived and verified. Subsequently, our study is extended to the complex networks that consist of multiple junctions and branches. By using the statistical method, we generate random loads with different attributes, i.e., resistive, inductive, or capacitive, and mainly study the effect of the number of branches and junctions on the frequency response of targeted load in various networks. From the perspective of protections for the targeted load in networks, results indicate that, for lossless and good dielectric (i.e., low-loss) media, it is crucial to consider the frequency responses at the critical frequencies in a periodical manner, rather than at a single frequency. Furthermore, it is worth noting that, the frequency response of targeted load behaves differently when varying the attributes of other loads in the network. The variation of network topology, i.e., increasing the number of junctions or branches, also influences the frequency response.

A numerical algorithm to evaluate the transient response for a synchronous scanning streak camera using a time-domain Baum–Liu–Tesche equation

The transient response is of great influence on the electromagnetic compatibility of synchronous scanning streak cameras (SSSCs). In this paper we propose a numerical method to evaluate the transient response of the scanning deflection plate (SDP). First, we created a simplified circuit model for the SDP used in an SSSC, and then derived the Baum–Liu–Tesche (BLT) equation in the frequency domain. From the frequency-domain BLT equation, its transient counterpart was derived. These parameters, together with the transient-BLT equation, were used to compute the transient load voltage and load current, and then a novel numerical method to fulfill the continuity equation was used. Several numerical simulations were conducted to verify this proposed method. The computed results were then compared with transient responses obtained by a frequency-domain/fast Fourier transform (FFT) method, and the accordance was excellent for highly conducting cables. The benefit of deriving the BLT equation in the time domain is that it may be used with slight modifications to calculate the transient response and the error can be controlled by a computer program. The result showed that the transient voltage was up to 1000V and the transient current was approximately 10A, so some protective measures should be taken to improve the electromagnetic compatibility.

Electromagnetic topology based fast algorithm for shielding effectiveness estimation of multiple enclosures with apertures

Shielding effectiveness (SE) estimation for an enclosure with apertures has been an attractive issue in electromagnetic compatibility (EMC) research area. Though many fast algorithms are developed for SE calculation, they mainly focus on the case of single cavity. Moreover, most of these methods neglect the wave coupling through apertures from enclosure to outside. A fast algorithm based on electromagnetic topology is proposed for calculating the SE of cascading multiple enclosures with apertures. In this algorithm, the wave coupling through apertures in both directions is taken into consideration. Firstly, the equivalent circuital model of cascading double enclosures and its signal flow graph of electromagnetic topology are given, followed by the derivation of scattering matrix of apertures node. Then propagation relationships at tube level and reflection relationships at node level are derived. As a result, the general BLT (Baum-Liu-Tesche) equation for voltage calculation at each node is established. Two major categories of cascading three enclosures with apertures are investigated. For serially cascading three enclosures, the general BLT equations are extended on the basis of BLT equations for cascading double enclosures, since the structures are a simple extension of them. For hybrid serially-parallelly cascading three enclosures, the common walls between the main enclosure and two sub-enclosures are considered as a topological node represented by a three-port network, whose scattering matrix is derived according to the definition of scattering parameters. Consequently, the general BLT equations for hybrid serially-parallelly cascading three enclosures are developed. Compared to the algorithms presented in the relevant literature, the topology-based algorithm proposed in this paper can not only calculate the shielding effectiveness for cascading multiple enclosures, but also lead to more accurate results in that the impedance of apertures is obtained through using diaphragms model. In order to validate the proposed method, a cascading double enclosures from a literature is chosen as an example. Calculated SE results are in good agreement with those in the literature. Then, three enclosures with different configurations and dimensions are also designed to validate the proposed method. Results from the proposed method are compared with those from the finite difference time domain (FDTD) method, and they are found to be in good agreement with each other. Experimental results also demonstrate the validation of the proposed method. Especially, the proposed method takes far less time to calculate SE than for FDTD method.

An averaged estimation of field strength into an enclosed large cavity with PCB board

ABSTRACTIn this article, two analysis methods, which are called as one is the combination of coplanar strip line analysis and Baum–Liu–Tesche (BLT) equation and the other combination of PoWer Balance (PWB) method and BLT equation, are used to predict the field strength level from the plane wave outside into an large enclosure with aperture and PCB boards inside. In realistic situations, an electrically large enclosure with an aperture has a drawback in calculating the field distribution inside the cavity precisely because of multiple reflections and resonance phenomena. Commercially available software based on the previously well‐established algorithms such as finite difference time domain (FDTD), finite element method (FEM), method of moment (MOM), and so on require much time consumption to carry out the field analysis within a limitation of accuracy, especially in the regime of high frequency. However, to overcome these resource and time‐consumption problem, PWB method based on statistical theory and BLT equation applying topological method are introduced and combined to give a reasonably good field estimation result. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2029–2031, 2015

Analysis of Shielded Twisted Pair Cable to External Field Coupling by Expanded Chain Matrix Modeling

In this paper, a numerical method for analyzing coupling between high-altitude electromagnetic pulse (HEMP) as external field and a shielded twisted pair (STP) cable is proposed, which is based on an expanded chain matrix. Load responses of electromagnetic (EM) field excitation in uniform transmission line (TL) are solved by Baum-Liu-Tesche (BLT) equations in frequency domain, however, it is difficult to apply BLT equations to solve load responses of STP cable because the iteratively changing configuration of each twisted pairs are involved in cable. To avoid this problem and decrease memory and CPU time, we proposed the expanded chain matrix modeling method that is calculated using ABCD parameters, and applied multi-conductor transmission line (MTL) theory to consider the EMP coupling effectiveness of each twisted pairs. The results implemented by the proposed method are presented and compared with those obtained by the finitedifference time domain (FDTD) method as a kind of 3D full wave analysis.

확률론과 위상학적 모델링을 이용한 이중 공진구조 내의 PCB 주파수 응답해석

Abstract In recent, the requirements for the safety to the effects of high power electromagnetic wave have been increased along with the development of electricity and electronic equipments. The small sized electronic devices and the various components have been analyzed by using the full-EM simulation and solving a complete set of Maxwell equation. However, the deterministic approach has a drawback and much limitation in the electromagnetic analysis of an electrically large cavity with a high complexity of the structure. In this paper, statistical theory and topological modeling method are combined to analyze the large cavity with a complex structure. In particular, the PWB(Power Balance) method and BLT(Baum-Liu-Tesche) equation are combined and employed to solve the frequency response to the large-scaled cavity with remarkably reduced time-consumption. For instance, a PCB substrate inside box of box are considered as a large structure with a complexity.Key words: Power Balance Method, Electromagnetic Compatibility, BLT Equation, Topological Analysis, Full Wave Analysis rsiJtsi!puviJ#(Department of Electronics, Telecommunication and Computer Engineering, Korea Aerospace University) *ru vOw(Electronics and Telecommunications Research Institute)Manuscript received July 7, 2014 ; Revised September 5, 2014 ; Accepted September 11, 2014. (ID No. 20140707-09S)Corresponding Author: Jae-Wook Lee (e-mail: jwlee1@kau.ac.kr)

Propagation and Responses of EMP on Transmission-Line Networks

This paper discusses the use of Baum-Liu-Tesche (BLT) equation for analyzing and calculating the propagation and load responses of transmission-line networks in frequency domain and time domain. The derivation and each parameters of BLT equation is introduced, and using BLT equation, two examples of specific coaxial cable networks are established, and the propagation and responses of networks are analyzed and calculated. The responses of networks terminals are measurement, and calculation results and measurement results are compared. The results show the excellent agreement between measurement and calculation results. The study results of this paper can be used for cable networks design and protection against EMP.