Yoshio Kami

Field coupling to nonuniform and uniform transmission lines

We study time-domain and frequency-domain responses of nonuniform and uniform transmission lines excited by incident electromagnetic waves. Externally excited uniform transmission lines permit closed-form solutions in terms of inverse chain matrix, whereas nonuniform lines cannot be analytically solved, in general. We adopt a method of equivalent cascaded network chain as the method of solving the latter situation. Useful and compact expressions for the load currents induced at terminal loads are derived. To confirm the validity of this method and the forcing terms, theoretical and experimental results of coupling calculations for a few typical (uniform/nonuniform) line geometries, relevant in the EMC field, are presented and discussed.

Analysis of crosstalk between finite-length microstrip lines: FDTD approach and circuit-concept modeling

Two approaches, one based on the circuit concept and the other based on field theory, are used to model the crosstalk between two microstrip lines of finite length and arbitrary orientation. In the circuit-concept modeling, a set of equations for the line voltages and currents has been derived from a modified telegraphers equation. A four-port network expression is resultantly obtained by solving the equations, thus the crosstalk can be predicted by applying terminal conditions to the network expression. On the other hand, the extended finite-difference time-domain (FDTD) method has been used to model the terminal resistors and the feeding resistive voltage source in the crosstalk analysis. Several physical models have been fabricated and experiments performed. The calculated results are compared to measurements. In our experiment, for microstrip lines of finite length and arbitrary orientation, there are short line-sections or vias at each of the four ports, which should be incorporated into the crosstalk analysis. This effect has been investigated numerically and experimentally.

Generation and Propagation of Common-Mode Currents in a Balanced Two-Conductor Line

Based on the transmission line theory, modal transformation is applied to a balanced two-conductor line connected to a signal source and a load, which yields an equivalent circuit expressed in differential and common modes. This newly developed equivalent circuit clearly shows that the common-mode currents on a balance two-conductor line are generated by (1) direct injection of the common-mode current by a connected RF source; (2) multiple mode conversions by the source and load; and (3) multiple reflections of the modal currents at the source and load. The effects of branch lines connected to the feeder line are also investigated, focusing on generation of the common-mode current. It is concluded that the common-mode currents are also generated by (4) series connection of a branch line. Particularly, in the case of a switching branch line, the connection of a feeder line makes the branch line imbalanced, resulting in the common-mode current in the branch line. The aforementioned theoretical findings are compared with computer simulation using the method of moments with the numerical electromagnetic code (NEC2).

Coupling Model of Crossing Transmission Lines

The coupling between transmission lines crossing diagonally is described. The resulting equations are derived by neglecting the recoupling of the line under induction (acceptor line (AL)) to the exciter line (EL). The coupling coefficients of various models are also considered. Equivalent-circuit representations for finite-length lines are obtained in two different forms: one expressed in terms of ideal voltage and ideal current sources, and the other in terms of ideal transformers, mutual inductance, and mutual capacitance. The first expressions are useful for predicting coupling between various types of lines. The second shows the coupling mechanism. The validity of the theory is confirmed by the experimental studies.

A new immunity test method

A new measurement system and a mapping technique for immunity or susceptibility testing are discussed. The most unique point of the system is that the electromagnetic (EM) fields are of slowly rotating polarization controlled electronically. In this paper, methods for generating slowly rotating fields are discussed. The direction of field polarization can be varied continuously and in a short time. By combining the method with a turntable, for example, the immunity-or susceptibility-characteristic maps can be obtained easily. This visualization technique is useful to detect the immunity or susceptibility attributes at a glance and thus may make the development of products with high immunity easy.

Modeling and Analysis of Crosstalk between Differential Lines in High-speed Interconnects

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.

Susceptibility characterization of a cavity with an aperture by using slowly rotating EM fields: FDTD analysis and measurements

This paper describes the evaluation of the susceptibility of a cavity with an aperture using the finite-difference time-domain (FDTD) method and experimentally. To reduce the computing time, the FDTD method is used for the radiation from the cavity and the susceptibility is obtained by using the reciprocity theorem. The cavity used here is modeled after a full-tower desktop enclosure with a 3.5-in bay. The susceptibility characteristics are evaluated by measuring outputs of a monopole antenna and transmission lines installed in the cavity. The susceptibility characteristics, using a three-dimensional (3-D) map, are studied from the computed and the measured results by applying slowly rotating electromagnetic fields to the cavity on a turntable. Measured and modeled results are in good agreement, indicating the merits of the proposed approach for susceptibility/immunity evaluation. Moreover, some discussions are made to check the susceptibility mechanism.

Crosstalk Of Finite-length Transmission Lines In Arbitrary Directions On The Same Ground Plane

Transmission lines in the proximity are not always in parallel directions but in arbitrary directions. In this paper, crosstalk or coupling between transmission lines in the arbitrary directions is studied by using a circuit concept. Under the condition of weak coupling, self-capacitances and self-inductances of the transmission lines can be approximated to be invariant in spite of existence of a proximate line. Mutual-capacitances and mutual-inductance is estimated by considering the coupling mechanism for an external electromagnetic field to a transmissicin line. To generalize our mode, a four-port network is also studied.

Crosstalk Analysis for Two Bent Lines Using Circuit Model

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 telegraphers 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.

Mode-Port-Network Approach to Analyze Power-Line EMC Problems for PLC

In Japan, a power-line communication (PLC) is in use as an indoor system in the frequency band of 2 MHz to 30 MHz. However, the radiated emission in this frequency band, which is caused by the common-mode current generated in the power-line systems, is a serious matter. To analyze the high-frequency behavior of the line system, a two-port-network model using differential- and common-mode ports is proposed here. As an example, the network-function expression is effectively used to analyze characteristics such as longitudinal conversion loss (LCL), induced common-mode currents in a power line having a load circuit, and an impedance stabilization network 1 (ISN1) attached to a PLC modem.