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.

To investigate electrostatic discharge (ESD) immunity testing for wearable electronic devices, the worst scenario i.e., an ESD event occurs when the body-mounted device approaches a grounded conductor is focused in this paper. 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 in lieu of actual wearable devices are measured. As a result, it is found that at a human charge voltage of 1kV, the peak current from the semi-sphere metal is large in order of the attachment of the waist (15.4A), arm (12.8A) and head (12.2A), whereas the peak current (10.0A) from the hand-held metal bar is the smallest. It is also found that the discharge currents through the semi-sphere metals decrease to zero at around 50ns regardless of the attachment positions, although the current through the hand-held metal bar continues to flow at over 90ns. These discharge currents are further characterized by the discharge resistance, the charge storage capacitance and the discharge time constant newly derived from the waveform energy, which are validated from the body impedance measured through the hand-held and body-mounted metals. The above finding suggests that ESD immunity test methods for wearable devices require test specifications entirely different from the conventional ESD immunity testing.

Electrostatic discharge (ESD) generators cause electromagnetic (EM) noises not only at ESD tests but also even before and after the tests. This may provide inconsistent test results, but the mechanism has not been well examined. To explain the mechanism qualitatively, we investigated a generation source model of EM noises from an ESD generator in conjunction with the functional control sequences of built-in relay switches and the DC high voltage power supply. To validate this model, we used a magnetic field probe to measure the induced EM noises before, during, and after contact and air discharges in accordance with the corresponding timing of the functional control sequences. As a result, we confirmed that the EM noises are induced when the relay switches operate before and at ESD testing and after ESD tests for both contact and air discharges. In addition, we found that the noise peaks due to contact discharges increase with charge voltages, and the peaks just before and at the testing are relatively larger than the ones after the tests, while the peaks of the induced noises at the air discharge testing do not always increase with charge voltages, but reach a maximum at 3kV. In addition, the peaks of the induced noises at the air discharge testing become smaller than either the peaks just before the testing and those after the tests at charge voltages above 6kV. This suggests that the EM noises just before ESD testing and after the test may cause the EUT to malfunction when air discharge tests with charge voltages over 6kV are conducted. A new control sequence of the built-in relay switch was also proposed for reducing the EM noises after ESD tests, which was validated through noise measurements.

The coupling response of an external transient electromagnetic field to a transmission line is considered. An experiment has been conducted to verify the line equations for a transmission line excited externally by a transient near field. The model field is generated by a monopole antenna installed in the vicinity of the transmission line and driven by a step waveform. The waveform is analyzed into discrete spectrum components using a Fourier transform. The frequency-domain field components affecting the transmission line are estimated by the moment method, and then the induced frequency-domain voltage at the terminal load is converted into a time-domain voltage using an inverse Fourier transform. Comparison between the measured and the computed values provides verification of the line equations. The coupling mechanism is discussed from the experimental results. It seems equivalently that the transmission line picks up the field, generated at the feed point and the top point of the monopole antenna, at both terminal ends.

A novel method for the radiated immunity test is proposed. The method is to generate controlled electromagnetic fields applying in arbitrary directions to an under test. The fields rotate at a low speed controlled electrically so that the immunity characteristics may be known in more detail. The primal characteristics of the fields generated by a trial benchtop setup are 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.

The crosstalk phenomenon, wich occurs between transmission lines, is caused by electromagnetic fields of currents flowing through the lines. Crosstalk between two bent lines is studied by using a set of solutions of modified telegrapher's equations. By expressing electromagnetic fields in terms of voltages and currents in the line ends, the resultant network function in the form of an ABCD matrix is obtained. Electromagnetic fields caused by currents flowing in risers at transmission line ends are taken into account in addition to those fields in line sections. The validity of the proposed approach was confirmed by comparing experimental results with computed results and those simulated by a commercial electromagnetic solver for some bent-line models.

In this paper, an experimental method is proposed for extracting the primary and secondary parameters of transmission lines with frequency dispersion. So far, there is no report of these methods being applied to transmission lines with frequency dispersion. This paper provides an experimental evaluation means of transmission lines with frequency dispersion and clarifies the issues when applying the proposed method. In the proposed experimental method, unnecessary components such as connectors are removed by using a simple de-embedding method. The frequency response of the primary and secondary parameters extracted by using the method reproduced all dispersion characteristics of a transmission line with frequency dispersion successfully. It is demonstrated that an accurate RLGC equivalent-circuit model is obtained experimentally, which can be used to quantitatively evaluate the frequency/time responses of shielded-FPC with frequency dispersion and to validate RLGC equivalent-circuit models extracted by using electromagnetic field analysis.

Mechanism for radiation phenomenon caused by a finite-length transmission line is discussed. Coupling of an external wave to a transmission line has been studied by using a circuit concept because of a TEM transmission. Since the relationship between coupling and radiation is reciprocal, radiation can be treated by using the circuit concept. It is shown that the equations obtained by using the field theory are quite coincident with those by the circuit theory. From the resultant, it can be concluded that the radiated fields are composed of those by the line current of TEM and the terminal currents. A method for an application of the circuit concept to radiation due to a trace on a printed circuit board is studied by comparing the experimental results.

A radiated immunity test method using fields in a three-dimensional Helmholtz-coil set is described. The incident field to equipment under test (EUT) is generated by an orthogonally structured three sets of Helmholtz coil. Using this structure, the resultant field can be generated with arbitrary amplitude and direction. Therefore, the three dimensional immunity characteristics of an EUT can be cleared. The resultant field is calculated numerically and it is established that the field distribution is uniform inside the three dimensional Helmholtz-coil set. This is also confirmed through comparison with measured results. As an example, the immunity test of a cathode ray tube (CRT) display is made and the immunity map of CRT is obtained without reseting placement of EUT. Such map makes us understand the physical meaning and weak points.

For actual multi-channel differential signaling system, the ideal balance or symmetrical topology cannot be established, and hence, an imbalance component is excited. However a theoretical analysis method of evaluating the voltage and current distribution on the differential-paired lines, which allows to anticipate EM radiation at the design stage and to study possible means for suppressing imbalance components, has not been implemented. To provide the basic considerations for electromagnetic (EM) radiation from practical asymmetrical differential-paired lines structure with equi-length routing used in high-speed board design, this paper newly proposes an analytical method for evaluating the voltage and current at any point on differential-paired lines by expressing the differential paired-lines with an equivalent source circuit and an equivalent load circuit. The proposed method can predict S-parameters, distributions of voltage and current and EM radiation with sufficient accuracy. In addition, the proposed method provides enough flexibility for different geometric parameters and can be used to develop physical insights and design guidelines. This study has successfully established a basic method to effectively predict signal integrity and EM interference issues on a differential-paired lines.

Fuzzy inference abilities were implemented to electromagnetic problems for the first time by the authors. After very successful results of applying the developed fuzzy modeling method to input impedance of a general monopole antenna, in this paper classifying the engineering electromagnetic problems simply, we apply the abilities of the proposed fuzzy inference method to make a qualitative model for transmission lines as a general example for a certain category of problems. The proposed approach starts from observing the problem through the window of human direct understandings and uses some parameters (as calculation base) evaluated basic for modeling process. It is shown that because of using this novel view point, a very simple fuzzy system based on new parameters may model the behavior of a transmission line in general form. The knowledge of each variable can be extracted and saved as simple curves individually, through continuing to make several models considering the desired variable as parameter. Finally, it is shown that the proposed method works even in highly nonuniform transmission line cases without changing in structure and complexity.

Common-mode excitation caused by an imperfect ground plane on a printed circuit board (PCB) has been conventionally explained with the 'current driven' scheme, in which the common-mode current is driven by the ground voltage across the unintentional inductance of the ground plane. We have developed an alternative method for estimating common-mode excitation that is driven by the difference of the common-mode voltages for two connected transmission lines. A parameter called current division factor (CDF) that represents the degree of imbalance of a transmission line explains the common-mode voltage. In this paper, we calculate the CDF with two-dimensional (2-D) static electric field analysis by using the boundary element method (BEM) for asymmetric transmission lines with an arbitrary cross-section. The proposed 2-D method requires less time than three-dimensional simulations. The EMI increase due to a signal line being close to the edge of the ground pattern was evaluated through CDF calculation. The estimated increase agreed well--within 2 dB--with the measured one.

This paper analyzes mechanisms of radiated emissions from multilayer printed circuit boards (PCBs) and presents a model to describe the characteristics of such radiation. The radiation mechanism from a four-layer PCB, including the internal power and ground planes, is investigated using a time-domain magnetic field measurement near the PCB. Measurement of the waveform indicates that the main source of radiation is in the power distribution planes. To investigate the characteristics of the radiation from the power distribution, the S21s of the board are measured; the board impedance and the transmission characteristics of the power distribution planes are found to be directly related to the S21 between the two points in the board. The results indicate that the power distribution acts as a transmission line at frequencies higher than 100 MHz. A model that can explain well the radiation properties of these planes treats them as a parallel-plate transmission line interconnected by decoupling circuit comprising a decoupling capacitor and interconnect inductance. From the transmission line theory it is deduced that the line resonance gives rise to strong radiated emissions. The interconnect inductance is an important factor in determining the radiation characteristics.

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.

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.

To evaluate frequency-domain interference between orthogonally intersecting stripline geometries, a lumped mutual capacitance was incorporated into a circuit model, and then a simplified circuit was proposed in the previous paper. The circuit model was approximated from an investigation of the distribution of mutual capacitance but it has remained how the capacitance is approximated. In this paper, a technique using an error function is proposed for the problem. Then, the time-domain response in an analytical expression is studied using the simplified circuit model in a Laplace transformation to make the mechanism clear. Comparing the experimental and the computed results verifies the proposed models.

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.