Faculty Profiles - TOYOTA Yoshitaka

MISC - TOYOTA Yoshitaka

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Connector Model for Use in Common-Mode Antenna Model Used to Estimate Radiation from Printed Circuit Boards with Board-to-Board Connector

Yuri Wakaduki, Tetsushi Watanabe, Yoshitaka Toyota, Kengo Iokibe, Liuji R. Koga, Osami Wada

IEICE TRANSACTIONS ON COMMUNICATIONS E99B ( 3 ) 695 - 702 2016.3

Language：English Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

A connector model expressed as an inductance is proposed for use in a previously reported common-mode antenna model. The common-mode antenna model is an equivalent model for estimating only common-mode radiation from a printed circuit board (PCB) more quickly and with less computational resources than a calculation method that fully divides the entire structure of the PCB into elemental cells, such as narrow signal traces and thin dielectric layers. Although the common-mode antenna model can estimate the amount of radiation on the basis of the pin configuration of the connector between two PCBs, the calculation results do not show the peak frequency shift in the radiation spectrum when there is a change in the pin configuration. A previous study suggested that the frequency shift depends on the total inductance of the connector, which led to the development of the connector model reported here, which takes into account the effective inductance of the connector. The common-mode antenna model with the developed connector model accurately simulates the peak frequency shift caused by a change in the connector pin configuration. The results agree well with measured spectra (error of 3 dB).

DOI： 10.1587/transcom.2015EBP3269

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Modeling of Current Probe and Simulation with Modal Equivalent Circuit in Common-mode Current Injection to Cable

115 ( 427 ) 65 - 70 2016.1

Suppression of mode conversion by installing bypass capacitor to power distribution network

Yoshitaka Toyota, Toshiki Mikura, Kengo Iokibe

IEEJ Transactions on Fundamentals and Materials 136 ( 1 ) 25 - 32 2016.1

Language：Japanese Publisher：Institute of Electrical Engineers of Japan

In the modal-equivalent circuit derived from the view of the mode-decomposition technique, mode-conversion sources are placed at the interface where the imbalance factor of the transmission lines changes. In addition, the amount of the mode-conversion sources is proportional to not only the difference in the imbalance factor but also the magnitudes of the normal-mode voltage and the common-mode current at the same position. In this paper, therefore, the suppression of mode conversion from normal mode to common mode is experimentally examined by installing a bypass capacitor to power distribution network. The bypass capacitor helps reduce the normal-mode voltage in the vicinity of a connector on a test board where mode conversion occurs so that the common-mode current flowing a power-line cable and the electric field far from the test board are decreased. In fact, the mode conversion was most suppressed when the bypass capacitor is placed closest to the connector on the test board. Also, it was found that the mode conversion was suppressed by the capacitor installed to the power-line cable in the vicinity of the connector.

DOI： 10.1541/ieejfms.136.25

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Analysis of side-channel information leaking behavior in cryptographic circuit using internal current source

Kengo Iokibe, Nobuhiro Tai, Hiroto Kagotani, Hiroyuki Onishi, Yoshitaka Toyota, Tetsushi Watanabe

IEEJ Transactions on Fundamentals and Materials 136 ( 6 ) 365 - 371 2016

Language：Japanese Publisher：Institute of Electrical Engineers of Japan

Cryptographic circuits were analyzed regarding their side-channel information leaking behavior based on internal current source. Cryptographic circuits were implemented in an FPGA with registers arranged to demonstrate three known side-channel information leaking behaviors
(1) leakage is reduced by making Hamming distance (HD) at registers constant, (2)leakage increases with signal-to-noise ratio of side-channel traces, and (3) unbalance of routing path from registers to load circuits produces leakage. The implemented circuits were measured in terms of voltage fluctuation in the power distribution network for FPGA core circuit where the circuits were implemented. The measured voltage fluctuations were converted into internal current sources that were exploited to analyze the information leaking behavior by applying a side-channel analysis, correlation power analysis (CPA). The analysis confirmed that internal current source clearly demonstrated the side-channel information leaking behaviors. This results suggests that internal current source would allow to understand what parts of encryption circuits largely contribute to leak information and how to develop an efficient and low-cost countermeasure against side-channel attacks.

DOI： 10.1541/ieejfms.136.365

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ディジタルICの電源供給回路網に付加するオンボードRLスナバの最適抵抗値決定式の導出

河田直樹, 吉野慎平, 矢野佑典, 五百旗頭健吾, 豊田啓孝

電気・情報関連学会中国支部連合大会講演論文集(CD-ROM) 67th 2016

暗号回路におけるサイドチャネル情報漏洩挙動の内部電流源による分析

五百旗頭健吾, 田井伸拓, 籠谷裕人, 大西紘之, 豊田啓孝, 渡辺哲史

電気学会論文誌 A 136 ( 6 ) 2016

近傍磁界分布測定を利用したサイドチャネル情報漏洩特性の分析

五百旗頭健吾, 矢野佑典, 豊田啓孝

電子情報通信学会大会講演論文集(CD-ROM) 2016 2016

損失を有する共振器型フィルタ実用化のための複雑形状の電源/GND層間の共振抑制評価

久保輝真, 五百旗頭健吾, 豊田啓孝

電子情報通信学会大会講演論文集(CD-ROM) 2016 2016

A Design Methodology of Lossy Resonator Filter Taking into Account Electric Characteristics of Ferrite Thin Film

115 ( 309 ) 31 - 36 2015.11

B-4-47 Optimization of On-board RL Snubber for Damping Resonance in Power Distribution Network for ICs

Iokibe Kengo, Kawata Naoki, Toyota Yoshitaka

Proceedings of the Society Conference of IEICE 2015 ( 1 ) 260 - 260 2015.8

Tightly Coupled Asymmetrically Tapered Bend in Differential Transmission Lines for High-density Mounting

115 ( 131 ) 49 - 54 2015.7

Suppression of Mode Conversion by Using Tightly Coupled Asymmetrically Tapered Bend in Differential Lines

Yoshitaka Toyota, Shohei Kan, Kengo Iokibe

IEICE TRANSACTIONS ON COMMUNICATIONS E98B ( 7 ) 1188 - 1195 2015.7

Language：English Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

In this paper, we propose a tightly coupled asymmetrically tapered bend to suppress differential-to-common mode conversion caused by bend discontinuity in a pair of differential lines. Tightly coupled symmetrically tapered bends have been so far proposed to suppress the mode conversion by decreasing the path difference in the bend. This approach makes the path difference shorter so that the differential lines are coupled more tightly but the path difference of twice the sum of the line width and the line separation still remains. To suppress the remaining path difference, this paper introduces the use of asymmetric tapers. In addition, two-section tapers are applied to reduce differential-mode reflection increased by the tapers and hence improve differential-mode propagation. A full-wave simulation of a right-angled bend demonstrates that the forward differential-to-common mode conversion is decreased by almost 30 dB compared to the symmetrically tapered bend and that the differential-mode reflection coefficient is reduced to the same amount as that of the classic bend. Also, the generality of the proposed bend structure is discussed.

DOI： 10.1587/transcom.E98.B.1188

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Planar EBG Structure with Ferrite Thin Film for Power-bus Noise Reduction (Electromagnetic Compatibility)

115 ( 114 ) 29 - 32 2015.6

Reduction in Common-mode Noise Generation by Placing Capacitors at Mode-conversion Positions in Power Distribution Network

115 ( 29 ) 7 - 12 2015.5

Investigation of low-frequency electromagnetic wave measurement using spin-polarized alkali metal atoms

115 ( 29 ) 43 - 48 2015.5

B-4-63 Effect of Common-mode Characteristic Impedance on Signal Integrity in Differential Transmission Lines

Takariki Keita, Kan Shohei, Toyota Yoshitaka, Iokibe Kengo

Proceedings of the IEICE General Conference 2015 ( 1 ) 353 - 353 2015.2

A Vialess Open-stub EBG Structure for Power-bus Noise Reduction

YAMASHITA Yuki, TOYOTA Yoshitaka, IOKIBE Kengo, KONDO Koichi, YOSHIDA Shigeyoshi, KANEKO Toshiyuki

IEICE technical report. Electromagnetic compatibility 114 ( 398 ) 57 - 62 2015.1

Language：Japanese Publisher：The Institute of Electronics, Information and Communication Engineers

Electromagnetic bandgap (EBG) formed by a periodic structure (EBG structure) has been studied for reducing power-bus noise of printed circuit boards. The EBG structure obtains a large amount of noise suppression and is available for separating simultaneous switching noise generated in digital circuits and small rf signal in analog circuits on mixed-signal boards. Many kinds of EBG structures have been so far proposed and can be roughly classified into two types with and without vias. We have focused on Planar EBG structures without vias because they consist of only two layers and cost-effective due to no vias. In contrast, open-stub EBG structure, which is one of EBG structures with vias, is easy to miniaturize its cell size independently of suppression frequency. We considered that the open-stub EBG structure was specialized for the EBG structures with vias. In this report, however, a planer EBG structure with open stub is proposed by inventing a new structure. The effect of power-bus noise reduction is examined by full-wave simulation and validated in the 2.4 GHz band.

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Effect of Mg loading on the high-frequency tunability of Ba0.8Sr0.2TiO3 ceramics

Takashi Teranishi, Tsuyoshi Sogabe, Hidetaka Hayashi, Akira Kishimoto, Kengo Iokibe, Yoshitaka Toyota

JAPANESE JOURNAL OF APPLIED PHYSICS 54 ( 1 ) 11502-1-011502-6 2015.1

Language：English Publisher：IOP PUBLISHING LTD

The effect of Mg loading on the high-frequency tunable properties and dielectric loss of Ba0.8Sr0.2Ti1-xMgxO3 (BSTM) ceramics was investigated. Variation in the lattice parameters and the 90 degrees domain configuration with Mg loading indicated a decrease in the tetragonal distortion. Additionally, the 90 degrees domain size decreased slightly with a low Mg loading, up to 0.1 mol %, resulting in a higher domain-wall density compared with the non-doped specimen. The 0.075 mol% Mg-loaded BSTM ceramic exhibited the highest tunability; this was attributed to the domain-size effect. The loss tangent (tan delta) roughly decreased with Mg loading, due to loaded oxygen vacancies. The maximum figure of merit value (FOM = tunability/tan delta) at 10 MHz was achieved for the 0.075 mol% Mg specimen, twice that of the non-doped specimen, due to an increase in the tunability and a decrease in the loss tangent with Mg loading. (C) 2015 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.54.011502

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線路接続部で生じるモード変換の等価回路モデル－モデルの妥当性とノイズ抑制に向けた検討－

豊田啓孝

電磁環境工学情報EMC 321 ( 9 ) 85 - 100 2015

Miniaturization of a Planar EBG Structure Using Interdigital Electrodes

Yuki Yamashita, Yoshitaka Toyota, Kengo Iokibe, Koichi Kondo, Shigeyoshi Yoshida, Toshiyuki Kaneko

2015 IEEE ELECTRICAL DESIGN OF ADVANCED PACKAGING AND SYSTEMS SYMPOSIUM 39 - 42 2015

Language：English Publisher：IEEE

This paper describes a proposed planar electromagnetic bandgap (EBG) structure whose unit cell size is miniaturized through the use of interdigital electrodes (IDEs). For planar EBG structures in general, it is difficult to miniaturize the cell size independently of stopband frequency because the stopband frequency depends on the cell size. For the proposed structure, however, the cell size can be miniaturized because the IDEs help enlarge the capacitance between adjacent unit cells and utilize a resonator formed in the unit cells. Because the resonator's resonant frequency determines the stopband frequency of an EBG structure with IDEs, the cell size can be miniaturized independently of the stopband frequency. In the work described in this paper, the proposed EBG structure's efficacy in reducing power bus noise was examined and evaluated through full-wave simulation and measurement in the wireless communication band. It was found that an IDE-EBG structure with a small (25 mm(2)) unit cell is a valid means for achieving power bus noise reduction.

DOI： 10.1109/EDAPS.2015.7383703

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