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Summary Relying on its strong nonlinear mapping ability, machine learning is found to be efficient and accurate for production prediction of fractured wells compared with conventional analytical methods, numerical simulations, and traditional decline curve analysis. However, its application in forecasting future multistep time series production remains challenging, with complications of error accumulation, growing uncertainty, and degraded accuracy. To this end, we propose a novel multistep ahead production prediction framework based on a bidirectional gated recurrent unit (BiGRU) and multitask learning (MTL) combined neural network (BiGRU-MTL), which can improve prediction performance by sharing task-dependent representations among tasks of multiphase production prediction. The forecasting strategies and evaluation setups for multiple timesteps are elaborated to avoid unfair assessment caused by mixing different prediction confidences over several days. In this framework, BiGRU is in charge of capturing nonlinear patterns of production variation by utilizing both forward and backward sequence information. MTL methods including cross-stitch network (CSN) and weighting losses with homoscedastic uncertainty are incorporated to automatically determine the sharing degree of multiple tasks and the weight ratio of the total loss function. By this means, domain knowledge contained in tasks of multiphase production prediction is deeply leveraged, shared, and coupled to enhance multistep ahead prediction accuracy while meeting the need for multiphase production forecasting. The proposed framework is applied to a synthetic well case, a field well case, and a field multiwell case to progressively prove the feasibility, robustness, and generalization of the BiGRU-MTL model. Experiment results show that the proposed framework outperforms conventional single-task models and commonly used recurrent neural networks (RNNs), furnishing a reliable and stable tool for accurate multistep ahead production prediction. This work promises to provide insights into dynamic production optimization and management in oil- and gasfield sites.

In recent years, the development of electronic devices are trending to be smaller and lighter, the techniques for suppressing electromagnetic (EM) radiation need to comply with these trends. EM shields are widely used to suppress EM radiation from transmission lines. EM shield for interconnection cable such as flexible-printed-circuits (FPC) requires flexibility of shielding-material. Consequently, EM shield becomes much more thin metallic shield and may be implemented near the transmission lines in the future. However, frequency response of the transmission coefficients of the shielded-FPC has dispersion due to insufficient shielding performance for near magnetic field. Elucidating the relationship between dispersion of frequency response and time response of transmission characteristics of shielded-FPC turns to be an important indicator of shielding techniques. In this paper, experimental extraction has been proposed for detailed investigating the frequency dispersion of shielded-FPC by using the RLGC equivalent-circuit model. The experimental extraction method used S-parameters measured by using vector network analyzer. The unnecessary components such as connectors are compensated correctly by using proposed method. The frequency response of primary and secondary parameters extracted using the proposed method reproduces all the dispersion characteristics of shielded-FPC successfully. More importantly, quantitative evaluation using the RLGC equivalent-circuit model considering dispersion characteristics can be performed experimentally.

Summary Domestic and foreign scholars have conducted extensive research on applying machine learning to post-fracture production prediction in recent decades and made great achievements in Bakken, Eagle Ford, Marcellus, and other large-scale oil and gas fields. However, few studies focus on small-sample production prediction of fractured wells, which is urgently needed in small-scale and newly developed reservoirs. In this work, we propose a novel small-sample production prediction framework based on multitask learning (MTL), including multitype data collection, task selection, data preprocessing, model training, and multitask production prediction. As for the trained model, feature extraction is first used through the deep hybrid network (DHN) by fully leveraging available multitype data such as numerical, sequence, and image. Then a multitask module based on the cross-stitch network (CSN) is integrated to automatically determine the information sharing degree of multiple production prediction tasks. In this way, data augmentation and model regularization are indirectly realized to handle the overfitting problem caused by insufficient training data. Finally, the proposed framework is applied to a small-sample field case with 59 fractured horizontal wells in northwest China. The comparison results show that the developed MTL-based model performs better than traditional single-task models in both prediction accuracy and learning efficiency. It provides an accurate and efficient tool for small-sample production prediction and can be used for reference to other small-sample domains in the petroleum industry.

ABSTRACT: Multi-cluster fracturing technology of horizontal wells is the main technical method for effective and economic development in tight reservoirs. The optimization of perforation location is the key to the simultaneous initiation of multiple clusters. Perforation locations are usually determined based on rock mechanics and in-situ stress conditions interpreted by logging and loboratory test. In this study, the parameters such as microscopic mineral composition , micropore and microfracture were introduced to establish a multi-scale data set. Besides, the equilibrium degree of fracture propagation is characterized by the multi-cluster uniform growth coefficient calculated by the perforation eroded area. Then, a fuzzy comprehensive evaluation was developed to analyze the influence of the multi-scale features on the uniform growth of fractures, and the mathematical relationship between them was established, the perforation location was optimized based on the relationship. Finally, the feasibility of the method is verified by case study. Our study results can provide us with more insights into the optimization of the multi-cluster fracture technology. 1. INTRODUCTION The development of a tight conglomerate reservoir is based on horizontal multi-cluster fracturing technology. In the process of treatments, multi-fractures often initiate and expand unevenly, which is directly due to the uneven flow distribution of each cluster. Scholars have conducted a large number of numerical simulation studies on the initiation and propagation mechanism of multiple fractures (Liu P. et al, 2016; Li L. et al, 2013; Wu K. et al, 2015; Fragacha et al, 2019). It is pointed out that the non-uniform propagation of multiple fractures is not only affected by reservoir heterogeneity and stress interference but also affected by perforation friction. Increasing perforation friction can promote fractures’ uniform initiation and propagation (Wu K. and Olson J. E., 2016). So, The behaviors of hydraulic fracture propagation are very complex. Hydraulic fracture field monitoring technology is an effective means to understand the shape of hydraulic fractures, which can be divided into indirect monitoring technology and direct monitoring technology. Indirect monitoring technology includes net pressure analysis, well test analysis, production analysis, etc. Direct monitoring technology can be subdivided into near-well zone monitoring technology and far-field zone monitoring technology. Near well zone monitoring technology includes radioactive tracer method, well temperature logging, well diameter logging, optical fiber monitoring (DTS/DAS), perforation imaging monitoring, etc (Barree R. et al, 2002; Roberts G. et al, 2018; Ugueto C. et al, 2016). Far-field zone monitoring technology includes microseismic monitoring, surface inclinometer monitoring, downhole inclination image monitoring of surrounding wells, deep shear wave imaging monitoring (DSWI), etc (Stolyarov S. et al, 2019; Xiu N. et al, 2020). Among them, perforation imaging monitoring technology can directly obtain a large number of high-definition perforation hole images. Calculating the eroded area of the perforation (the area change of the perforation pre-and post-fracturing) can reflect the abrasion degree of the perforation and judge the sand inflow of the fracture.

ABSTRACT: Accurate shear wave velocity (Vs) is essential for determining reservoir rock mechanical parameters and pore structure of tight oil, whereas it is usually not measured in well logging due to high costs. The simple conversion of compressional wave velocity (Vp) to Vs introduces significant uncertainty to calculation results. To this end, we propose to construct an efficient and robust Vs prediction model using Gated Recurrent Unit (GRU) network, which could deeply mine and connect the information in Vs sequence and other logging sequences (e.g., gamma ray, resistivity, neutron porosity and Vp). Based on the collected logging data set, the GRU prediction model for predicting Vs is trained, validated and tested, which can predict Vs in the missing sections according to synthetic logging data and depth correlation. The optimal hyperparameters of the proposed model, including the number of layers, the number of neurons, activation function and learning rate are explored via the Bayesian optimization algorithm. The field experiment shows that the proposed Vs prediction model outperforms the traditional conversion method and can be used as a promising tool for accurate Vs prediction. 1. INTRODUCTION The key to the successful development of shale gas and tight oil lies in horizontal drilling and hydraulic fracturing techniques that can break up tight reservoirs for effective connectivity (Junfeng et al., 2015; Longde et al., 2019; Ning et al., 2018; Wendong et al., 2013; Xiaoxia et al., 2014). Notably, rock elasticity, such as Young’s modulus and Poisson’s ratio, plays an important role in the fracturing and production effectiveness of fractured horizontal wells. Most of the parameters characterizing the elastic properties can be calculated from compressional wave velocity (Vp), shear wave velocity (Vs) and density. Currently, Vp and density can usually be easily obtained by conventional logging, but Vs are often missing due to the high cost of the dipole acoustic wave measurements (Gholami et al., 2014; X.-Y. Li & Zhang, 2011; Jun Wang et al., 2020). On the other hand, not only rock elastic properties but Vs is also important for prestack inversion (Pei-Jie & Xing-Yao, 2008), reservoir description (Wegener et al., 2006) and the identification of fluid distribution (Hamada, 2004). Therefore, the urgent need for accurate prediction of Vs has raised the wide interest of foreign and domestic researchers.

S-wave velocity (Vs) is a critical petrophysical parameter for reservoir characterization. It is desirable to predict Vs based on conventional logging data, but the logging cost is high. Therefore, a deep hybrid neural network coupling the convolutional neural network (CNN), Stacked gated recurrent unit (SGRU) is proposed to predict the Vs, where the inputs to the model are drill cutting features. In the proposed CNN-SGRU hybrid model, CNN is adopted to capture the spatial features from the input data, and SGRU is used to extract the temporal patterns of variation from both the forward and backward directions. To illustrate the prediction effect, the glutenite reservoir in the Baikouquan Formation of Mahu Sag, Junggar Basin is taken as an example. Mineral and pore information of drill cuttings, including siliciclastic content, clay content, quartz content, and void area ratio is chosen as the input data of the CNN-SGRU hybrid model. Three indices are used to quantitatively evaluate the prediction performance, including Mean absolute percentage error (MAPE), Root mean square error (RMSE), and Mean absolute error (MAE). The results show that the prediction accuracy of the proposed model is higher than that of the Xu-White model, CNN, and GRU. Furthermore, the results indicate that drill cuttings can replace logging data to predict Vs.

Production prediction plays an important role in decision making, development planning, and economic evaluation during the exploration and development period. However, applying traditional methods for production forecasting of newly developed wells in the conglomerate reservoir is restricted by limited historical data, complex fracture propagation, and frequent operational changes. This study proposed a Gated Recurrent Unit (GRU) neural network-based model to achieve batch production forecasting in M conglomerate reservoir of China, which tackles the limitations of traditional decline curve analysis and conventional time-series prediction methods. The model is trained by four features of production rate, tubing pressure (TP), choke size (CS), and shut-in period (SI) from 70 multistage hydraulic fractured horizontal wells. Firstly, a comprehensive data preprocessing is implemented, including excluding unfit wells, data screening, feature selection, partitioning data set, z-score normalization, and format conversion. Then, the four-feature model is compared with the model considering production only, and it is found that with frequent oilfield operations changes, the four-feature model could accurately capture the complex variance pattern of production rate. Further, Random Forest (RF) is employed to optimize the prediction results of GRU. For a fair evaluation, the performance of the proposed model is compared with that of simple Recurrent Neural Network (RNN) and Long Short-Term Memory (LSTM) neural network. The results show that the proposed approach outperforms the others in prediction accuracy and generalization ability. It is worth mentioning that under the guidance of continuous learning, the GRU model can be updated as soon as more wells become available.

This paper presents a method for evaluating the spatial resolution of an optical electric field sensor with a dipole element by measurement. The electromagnetic wave radiated from a standard horn antenna was applied perpendicularly to a flat metal surface, and the electric field distribution of the generated standing wave was measured while moving the optical electric field sensor with a step width smaller than the element length. It evaluated by calculating the theoretical value of ideal dipole element length dependence by 0.1mm step. As a result, it was found that a spatial resolution equivalent to the element length can be expected with a deviation within 2.15 dB when the element length is 1 cm and the frequency is 2.5 GHz.

With the gowning demand of improving quality and benefit of unconventional resources, time-series production prediction plays an increasingly essential role in economic investment, stimulation scale and decision making. However, due to the limitations of traditional model-driven methods and data-driven methods, production forecasting is still challenging. In this paper, we propose a novel framework using Bidirectional Gated Recurrent Unit (Bi-GRU) and Sparrow Search Algorithm (SSA) that improves the accuracy of oil rate forecasting. The Bi-GRU could make full use of both past and future information inside production sequences and related features. SSA is employed for hyperparameter tuning of the Bi-GRU model. To validate the feasibility, robustness and efficiency of the proposed method, three cases are carried out from the perspective of an ideal single well from the simulation model, an actual single well under variable production constraints and actual multiple wells. Model performance is compared with traditional decline curve analysis, conventional time series methods and one-way recurrent neural networks. The observations show that the proposed method performs better than the others in terms of accuracy and robustness.

The coalbed methane blocks are always structurally and topographically complex, and there are no models to accurately predict the coalbed methane content in the southern Sichuan Basin, China. This study proposes a feasible machine learning model to achieve a more accurate estimation of coalbed methane content with a small data set. A revised estimate of depth (Z) based on hydrogeological grounds was used as a feature of the prediction model, which can resolve the errors introduced by using the commonly used measured depth as a feature in areas with drastic topographical and structural changes. The revised estimate of depth (Z) and the measured depth were applied for data analysis along with three machine learning algorithms (support vector regression, gradient boosting decision tree, and CatBoost) to obtain the optimized model for coalbed methane content estimation. Modeling results show that the coefficient of determination (R2), mean absolute error, and mean square error of all algorithms were improved after replacing the measured depth with the revised estimate of depth (Z). The Catboost algorithm performed better than the other two algorithms in this study. The prediction results based on CatBoost using the revised estimate of depth (Z) showed the highest accuracy among all the comparison models. The analysis results show that the R2 between Z and coalbed methane content was 150% higher than that between measured depth and coalbed methane content. This vast difference between measured depth and revised estimate of depth (Z) outputs was caused by drastic changes in topography and structure.

In the design of transmission line, sometimes it is required to pursue a solution which satisfies simultaneously multiobjective (electrical, mechanical, and thermal) performances even including conflicting requirements. This paper newly attempts to propose a multi-objective satisfactory design method, Preference Set-Based Design (PSD), to the design of a transmission line referenced to a meshed ground plane. This work demonstrates that PSD method is applicable for multi-objective design of transmission line from the viewpoint of SI and EMI performances. The design parameters of a simple transmission line referenced to the meshed ground plane, which satisfy required performance, are obtained successfully in ranges by PSD. The validity of the proposed method is demonstrated.

In the design of electric and electronic devices, it is required to pursue a solution which satisfies simultaneously multi-objective performances sometimes including conflicting requirements. This paper newly attempts to propose a concurrent design method in electrical and electronic engineering by applying a multi-objective satisfactory design method, Preference Set-Based Design (PSD), to differential-paired lines with meander delay line. The meander delay line for the equi-length routing are designed using PSD. The design parameters satisfying required performances are obtained in ranges successfully. The validity of the design parameters is demonstrated by numerical modeling. It was demonstrated that PSD is applicable for multi-objective design under the uncertainty problems.

Due to the fast spread of the electric cars and the advanced driver assistance systems in recent years, it is necessary to reduce the electromagnetic noise from the power electronics, which are usually in high speed and with large electricity, and in the meantime to improve the immunity performances of sensing apparatus and communication equipment. The electromagnetic environmental compatibility in the cars will be of more importance in future. In this work, the behavior of electromagnetic waves generated in automotive cabin was estimated by a use of simulation techniques for the case where electromagnetic waves were irradiated into the simple cabin from outside, and we propose a new method to analyze electromagnetic waves propagating in automotive cabin by using Poynting's theorem.

In the design of electric and electronic devices, it is required to pursue a solution which satisfies simultaneously multi-objective performances sometimes including conflicting requirements. This paper newly attempt to propose a concurrent design method for a multi-objective satisfactory design method, Preference Set-Based Design (PSD), to a transmission line (TL) with impedance resonators for realizing negative group delay and slope characteristics. The TL is consisted of four different resonators with different resonant frequency. The design parameters of the TL are obtained in ranges by PSD. The validity of the design parameters is demonstrated by numerical modeling.

An estimation method of the induced current of a transmission line under the bulk current injection (BCI) test is presented. In this method, the influence of the current injected by the BCI probe is expressed using the equivalent voltage and current sources. By modelling the transmission line loaded with the BCI probe as a 3-port network, an absolute value of the induced current of transmission line can be estimated analytically without using numerical simulation. To validate the proposed method, the calculated results are shown and compared with the experimental results.

In a bulk current injection test (BCI test), an electric current is injected into a wire harness connected to an electronic equipment. Since this test setup can be considered as a transmission line exposed to an external electromagnetic field, the relation of the line voltage and current is expressed by a modified telegrapher's equation. This paper reveals an analytical method of the BCI-test system using the circuit concept approach, and its effectiveness is experimentally verif ed. Furthermore, the difference between the susceptibility of transmission line exposed to the plane-EM field and that under the BCI test is shown as an example.

It is notable that the air discharge method specified in the International Eelectrotechnical Commission (IEC) standard provides unstable testing reproducibility. In this paper, to achieve stable testing reproducibility, we proposed an alternative air discharge test method using an electrostatic discharge (ESD) generator in contact discharge mode. Measurements of air discharge currents through a fixed gap to sphere or conical electrodes in view of various metal curvatures inside equipment covered with a non-conductive case were conducted with respect to different gap lengths from 1 mm to 6 mm, and their current peaks and rise time were investigated in conjunction with the statistical variations. Comparison with air discharge current waveforms was also made to reveal better testing repeatability for the proposed method.

Multi-objective optimization methods are applied to solve various issues in fields of not only mechanical engineering but also management, medicine, etc. Preference set-based design (PSD) method is one of them and has been successfully applied in the mechanical engineering field. We have discussed the utility when applying the PSD method to solve various electrical and electronics problems. In this study, the layout design problem for microstrip line (MSL) placed on a board edge to satisfy required performances is investigated. When applying the PSD method to the problem, a meta-modeling with a response surface methodology (RSM) to determine RLGC parameters of the MSL is proposed, and then the validity is discussed.

In this work, based on the mode decomposition technique and the far-field Green's function, an analytical solution of the radiated electric field from coupled traces is formulated by taking both the common and differential-mode currents into consideration. The analytical solution of the radiated electric field is further used to predict the EMI from differential microstrip pairs with time-domain input signals having different slew rates and different amount of skew. From the results, it is possible to quantify the relative impact of these two sources of imbalance on EMI.

Crosstalk between lossless multiconductor lines is analyzed using a mode decomposition technique in the time domain. An approach that mode voltages and currents at an arbitrary point along the lines are expressed in terms of the initially incident mode sources and the mode reflection coefficients is proposed. The results obtained by the approach offer insight into how each mode component influences the crosstalk waveform. A SPICE equivalent circuit is also developed based on the approach. The validity of our approach and the SPICE model is investigated by comparing the results with those from fast Fourier transform simulations.

In this paper the time-domain analysis of two parallel traces is investigated. First, the telegrapher's equations for transmission line are applied to the parallel traces on printed circuit board (PCB), and are solved by using the mode decomposition technique. The time-domain solutions are then obtained by using the inverse Laplace transform. Although the Fourier-transform technique is also applicable for this problem, the solution is given numerically. Contrarily, the inverse Laplace transform successfully leads to an analytical expression for the transmission characteristics. The analytical expression is represented by series, which clearly explains the coupling mechanism. The analytical expression for the fundamental section of a meander delay line is investigated in detail. The analytical solution is validated by measurements, and the characteristics of the distortions in the output waveforms of meander delay lines due to the crosstalk are also investigated.

An analytical method for estimating coupling between microstrip lines in arbitrary directions on adjacent layers in multi-layer printed circuit boards is studied: one line is embedded and the other is on the surface layer. Coupling or crosstalk has been estimated by development of a circuit-concept approach based on modified telegrapher's equations of the Agrawal approach instead of the Taylor approach for some computational advantages. Electromagnetic fields from the embedded microstrip line and the microstrip line on the surface can be obtained by using the electric image method for dielectric substrates. To verify the proposed approach, we conducted some experiments and compared the results of our approach with those of measurement and a commercial electromagnetic solver.

A new radio-frequency (RF) radiated immunity/susceptibility test method using four-septum TEM cell is proposed. A rotating-EM field can be generated inside the cell by feeding four-different RF DSB-SC signals to four septa arranged in the cell. Since a polarization plane of the rotating-EM field rotates in a low speed, the immunity/susceptibility test for the EM field with various polarizations can be conducted more easily. In this paper, a technique for generating the rotating-EM field in the cell is investigated. The basic characteristics of the cell and the rotating-EM field by using the technique are clarified. To verify the validity of this test method, a RF radiated susceptibility of a printed circuit board is measured. The measured results are verified by comparing with the theoretical results based on modified telegrapher's equations.

We propose a method of crosstalk analysis for two bent transmission lines with vias at both ends on a PCB using a circuit-concept approach in the quasi-static condition. In this condition, the electromagnetic fields can be approximately estimated by the quasi-static terms of the accurate Green's function in an inhomogeneous medium. Thus we obtain a circuit model in an ABCD matrix by taking account of the fields generated by a longitudinal line and a vertical via on a PCB. To verify the proposed approach, we conducted some experiments and compared our approach's results with measured results and a commercial electromagnetic solver's results.

The crosstalks between a single-ended line and a differential pair in parallel are analyzed using telegrapher's equations for multiconductor lines. The crosstalk from the single-ended trace to the differential pair is estimated at shunt-arm resistors in T or π termination networks. The analysis is conducted by incorporating the termination conditions with the solution of the telegrapher's equations. The time-domain characteristics of the crosstalk are obtained by using the fast inverse Laplace transform. The measurements are conducted easily by using a single-ended digital oscilloscope since the crosstalk is evaluated on the shunt-arm resistors. Both the calculated and measured results are presented, and the characteristics of the crosstalk are also investigated qualitatively.

The crosstalk between a single-ended line and a differential pair, and between differential pairs are investigated in this paper. First, the telegrapher’s equations for multiconductor line are applied. Then the telegrapher’s equations are solved by using the mode decomposition technique. Finally the mixed-mode S-parameters are derived to investigate the crosstalk and mode conversion.

Crosstalk and its reduction by using stitching capacitors for traces crossing split ground plane are investigated in this paper. While two traces cross the same slot in the ground plane, the crosstalk between them will be of very high level, even if they are far apart. By examining the measured S-parameter and near-magnetic field, we concluded that the crosstalk is due to magnetic or inductive coupling between the trace and the slot in the ground. We therefore developed an equivalent circuit model for characterizing the crosstalk. The validity of the equivalent circuit model is verified by comparison with measurement results. The reduction of crosstalk by stitching the split ground plane with capacitors is discussed on the basis of the developed equivalent circuit model. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(8): 26– 34, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20338

Wearable electronic devices have proliferated in recent years. Since such devices are used by attaching to a human, every time the human is electrically charged or discharged, the electric potential of such a wearable device abruptly changes. Thus the device is exposed in close proximity to the resultant transient electromagnetic fields, which may cause malfunctions in the device. Electrostatic discharge (ESD) immunity test methods that assume this situation are not yet developed in the present international standards. In this study, to investigate such ESD immunity testing, we considered the worst case as an ESD event which occurs when the body-mounted wearable device approaches a grounded conductor. In lieu of actual devices, we measured discharge currents caused by air discharges from a charged human through a hand-held metal bar or through a semi-sphere metal attached to the head, arm or waist. As a result, we found that at a human charge voltage of 1 kV, the peak current from the semi-sphere metal is large in order of the attachment of the waist (15.4 A), arm (12.8 A) and head (12.2 A), whereas the peak current (10.0 A) from the hand-held metal bar is the smallest. It was also found that the discharge currents from the semi-sphere metal decrease at around 50 ns regardless of the attachment positions, however, the current from the handheld metal bar continues to flow at over 90 ns. This suggests that ESD immunity testing for wearable devices needs different specifications of test equipment and test method from the conventional testing.

Electrical design is usually made with the concepts based on electric circuit theory. Nowadays it needs to consider the electromagnetic (EM) field generated in devices, components, and equipment to achieve their expected performances and satisfy the electromagnetic compatibility (EMC) regulations as well. In such kind of design, EM-fiel simulators are often used to estimate EM-fieIl effects to circuit performances. In this paper, the application of a multi-objective satisfactory design method to electrical design is discussed. The method, named preference set-based design (PSD), is developed as a concurrent design method in a fiel of mechanical engineerings. The PSD method is a sort of synthesis technique to optimize multi purposes concurrently. As a firs model to electric and electronics fields the method is applied to filte designs and its usefulness is discussed. Applied filter are an ordinary f ve-order low-pass filte and an electromagnetic interference (EMI) filte composed of plural element parameters and objectives or performances of attenuation characteristics. In practical cases, some unclear parameters should be taken into account, for example a terminal load in some range, and a coupling coefficien in a common-mode chock for EMI filte. Such an uncertainty problem is treated in this study. By using the resultant parameter sets, the attenuation characteristics are analyzed and confirme whether the performances are satisfie with the required performances.

As automotive electronics have increased, models for predicting the transmission characteristics of wiring harnesses, suitable for the automotive EMC tests, are needed. In this paper, the repetitive structures of the cross-sectional shape of the twisted pair cable is focused on. By taking account of RLGC parameters, a theoretical analysis modeling for whole cables, based on multi-conductor transmission line theory, is proposed. Furthermore, the theoretical values are compared with measured values and a full-wave simulator. In case that a twisted pitch, a length of the cable, and a height of reference ground plane are changed, the validity of the proposed model is confirmed.

Nowadays differential traces as interconnects are extensively used since the electromagnetic radiation can be ideally cancelled by the out-of-phase and same amplitude signals on the two tightly coupled differential traces. However, the ability of differential pair in mitigating EM interference (EMI) may be seriously jeopardized by possible unbalance of the excitation, since both the common mode and the differential mode current may introduced to the differential pair. In this work, based on the mode decomposition technique and the far-field Green's function, an analytical solution of the radiated electric field from coupled traces is formulated by taking both the common and differential-mode currents into consideration. Thus the radiated electric field from any arbitrary excitation can be easily calculated. The validity of the analytical formulation is verified by comparing the calculated results with the full-wave simulation results.

The four-septum transverse electromagnetic (TEM) cell is like the traditional TEM cell but has four plate-like septa in the internal space. A slowly rotating field can be easily generated in the four-septum TEM cell, thus radiated immunity/susceptibility characteristics of an EUT under arbitrary specific polarizations can be measured without rearranging the test setup. A design approach for the four-septum TEM cell is discussed in this paper. The characteristics of the cell are analyzed based on the telegrapher's equation and decomposition of the transmission mode into four independent modes. Then a design approach is given based on the analytical results. A prototype of the four-septum TEM cell based on the design is constructed and the characteristics of the prototype cell are experimentally evaluated. The validity and effectiveness of the design approach are confirmed.

Crosstalk or coupling phenomenon between two parallel conductors with a ground or reference conductor is well known in electromagnetic compatibility and microwave circuit fields. In this paper we consider the characteristics of a long two-conductor line embedded in an inhomogeneous medium while taking account of the difference between two phase constants in independent propagation modes of two parallel lines. The characteristics of near-end and far-end crosstalk and of through-end transmission are discussed for frequencies up to more than the frequency where the line length is 10 times the wavelength. Interesting properties, such as very strong and null crosstalk phenomena that occur at the far end and non-transmission at the through end, appear in the envelope characteristics. The reason for these properties is clarified by making theoretical and experimental investigations.

A seven-port wave-correlator based vector network analyzer is proposed. The seven-port wave-correlator is a combination of two six-port wave-correlators which share common components. Furthermore, the complex wave ratio measurement accuracy is improved since the input signals can be directly detected by the side-arm ports. A seven-port wave-correlator is fabricated using microstrip branch line couplers. The performance of the wave-correlator and the constructed network analyzer are evaluated, and the measurement accuracy is confirmed.

An immunity/susceptibility test method using electromagnetic waves of rotating polarization is described and test results are discussed. Low-rate rotation of the field polarization is controlled electrically and continuously in a two-dimensional plane, so that radiated immunity/susceptibility characteristics that are three-dimensionally depicted can be obtained by using a turntable together with this method. This paper explains how the rotating fields are generated, and discusses experimentally measured characteristics of several test examples. The results show the effectiveness of the proposed method for quickly visualizing the weak/strong immunity/susceptibility directions, demonstrating its usefulness for application in the trial phase of a product development.