# Electrical and Electromagnetic Circuit (Wada Lab)

**Research into circuit systems**

Electric network science is a fundamental field of electrical and electronic engineering, and these days complex electric circuit systems are increasingly found on tiny semiconductors. It is necessary to take many factors into account when designing such systems —from the characteristics of materials to the arrangement of components, and even mutual interference between components. In addition, a new body of theory is necessary for tackling the challenges of advancing and expanding the functionality of electric power, communications, and computing systems. This theory involves treating devices, circuits, and systems by integrating them. In this lab, we take up a wide range of challenges to address these demands—covering linear and nonlinear electric and electronic circuits, analog and digital signal processing circuits, device modeling, dealing with practical issues in high-speed digital systems and power systems, modeling of phenomena and systems for solving problems, elucidation of electromagnetic phenomena, development of new system design methods and hardware algorithms for these, and the development of design methods for circuits and systems featuring electromagnetic coupling.

## Academic Staff

### Osami WADA

Professor (Graduate School of Engineering)

**Research Interests**

- Electrical and electromagnetic circuits
- Electronic circuits, electromagnetic waves, electromagnetic compatibility (EMC)
- Evaluation, modeling and simulation of high-frequency characteristics of passive interconnections
- Evaluation, modeling and simulation of EMC characteristics of semiconductor devices
- EMC design of analog and digital circuits

**Classes**

- Electric and Electronic Circuits
- Electrical and Electromagnetic (graduate school)

**Contacts**

Katsura Campus A1-401

TEL: +81-75-383-2244

FAX: +81-75-383-2245

E-mail: wada(at)kuee.kyoto-u.ac.jp

### Takashi HISAKADO

Associate Professor (Graduate School of Engineering)

**Research Interests**

- Circuit system
- Modeling of electromagnetic phenomena
- Power flow design

**Contacts**

Katsura Bld. A1 Rm.404

TEL: +81-75-383-2248

FAX: +81-75-383-2248

E-mail: hisakado＠kuee.kyoto-u.ac.jp

### A.K.M. Mahfuzul ISLAM

Junior Associate Professor (Graduate School of Engineering)

**Research Interests**

- Characterization and modeling of noise in MOS transistors
- Low-power CMOS sensor circuits
- On-chip monitors

**Contacts**

Katsura Campus A1-402

TEL: +81-75-383-2246

FAX: +81-75-383-2245

E-mail: islam.akmmahfuzul.3w @ kyoto-u.ac.jp

## Introduction to R&D Topics

### Basic theory of circuit systems

As a basic theory for circuit systems, we apply mathematics and physics theory to circuit network analysis to clarify various phenomena in circuits and develop techniques that are useful for circuit design. Currently, we are tackling the following research in the area of basic circuit systems theory.

- Circuit analysis using Groebner basis
- Techniques for searching solutions in parameter spaces using complex homotopy
- Complete solution search techniques using interval arithmetic
- Algorithms with precision assurance
- Application of Laplace transformations, wavelet transformation, etc.
- Analysis of integrable circuits

### Distributed constant systems

The circuit theory of lumped parameter that is supporting the evolution of today's electric and electronic circuits is derived using refined approximations of Maxwell's equations, which describe electromagnetic fields. However, as the operating frequency of circuit systems steadily increases there is a growing need to treat circuits as distributed constant lines and electromagnetic field phenomenon. To address this need, this lab is working on developing new analysis techniques and on modeling projects.

- Common mode traveling wave analysis using electromagnetic field theory
- Distributed constant line fault location
- Distributed constant line identification using the inverse scattering method

### Development of hardware algorithms

To solve problems using computers, the problem is simulated by representing it with physical circuit phenomena and then obtaining a solution to the problem. The advent of flexible hardware with the FPGA has made it possible to simulate the structure of individual problems with circuits. This lab is pursuing research in the following areas:

- Development of hardware algorithms using FPGAs
- Design of low power consumption circuits using reciprocal circuits
- Development of hardware using Gray code
- Development of hardware using nonlinearity

### Research on EMC design for electronic circuits

In the design of electronic circuits, it is important to ensure electromagnetic compatibility (EMC) performance—that is, operation without emitting EM noise to the surroundings, and without susceptibility to external sources of EM interference. We are pursuing the following research in the area of EMC design of electronic circuits:

- EMC package design methods for digital circuits and devices
- Development of LSI macro models for low noise design of digital circuits

### Research on modeling and design methods for high-speed, high-frequency circuits

In order to design high-speed circuits that have advanced functions, the design needs account for not just the circuit network, but also the EM coupling generated by the three-dimensional structure made up of the circuit boards, semiconductor packages, and other elements, which make up the circuit. High-speed digital circuits must be considered to be essentially high-frequency circuits. Even very slight levels of unwanted EM coupling can have a large impact on circuit characteristics of high-frequency circuits. In view of this, we are working to develop analysis techniques for the electrical characteristics of circuit boards and semiconductor packages and to develop circuit design techniques.