Faculty Profiles - TOYOTA Yoshitaka

MISC - TOYOTA Yoshitaka

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ディジタルIC電源供給回路へのRLスナバ適用による伝導性電磁雑音低減及び電源品質改善

五百旗頭健吾, 山縣亮介, 豊田啓孝

電子情報通信学会論文誌B J97-B ( 7 ) 497 - 506 2014

Modal Equivalent Circuit of Bend Discontinuity in Differential Transmission Lines

Yoshitaka Toyota, Shohei Kan, Kengo Iokibe

2014 INTERNATIONAL SYMPOSIUM ON ELECTROMAGNETIC COMPATIBILITY, TOKYO (EMC'14/TOKYO) 117 - 120 2014

Language：English Publisher：IEEE

The equivalent-circuit expression of bend discontinuity in differential transmission lines, which is derived from the view of the mode-decomposition technique, is proposed in this paper. We investigated the relationship between the amount of mode conversion in the bend region and two components in the modal equivalent circuit: the mode-conversion sources and the modal reactances (modal inductances and capacitances). As a result, it was found that not only the difference in the imbalance factor but also the magnitude of the modal reactances can have a lot of effect on the mode conversion.

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Ferrite-covered Open Stub as Lossy Resonator Filter for Suppressing Noise Propagation in Power Bus

Yoshitaka Toyota, Kengo Iokibe, Koichi Kondo, Shigeyoshi Yoshida

2014 INTERNATIONAL SYMPOSIUM ON ELECTROMAGNETIC COMPATIBILITY (EMC EUROPE) 765 - 769 2014

Language：English Publisher：IEEE

A lossy resonator filter with frequency selectivity and low loss, which suppresses noise propagation in the power-ground plane pair of a printed circuit board (PCB) at high frequencies (over 1 GHz), was fabricated and evaluated. A ferrite-covered open stub was formed on a PCB as a lossy resonator filter, and its characteristics were verified by measurement using a vector network analyzer as well as full-wave simulation. The measurement and simulation results show that the noise in the power bus of the PCB at frequencies over 1 GHz is suppressed. Even in the case that the power bus is inside the board, noise propagation in the power bus was suppressed by connecting the inside ground plane and the ground plane of the lossy resonator filter by vias in order to conduct the noise to the filter.

DOI： 10.1109/EMCEurope.2014.6931007

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Guard Trace with Periodic Structure for Reducing Common-mode Radiation and Maintaining Signal Integrity

Yuho Terai, Yoshitaka Toyota, Kengo Iokibe, Tetsushi Watanabe

2014 INTERNATIONAL SYMPOSIUM ON ELECTROMAGNETIC COMPATIBILITY, TOKYO (EMC'14/TOKYO) 545 - 548 2014

Language：English Publisher：IEEE

The guard trace is effective for suppressing common-mode generation caused by placing a signal trace close to the return edge on a printed circuit board. Our previous studies on the guard trace focused only on a design methodology for reducing common-mode radiation, but the placing guard trace close to the signal line increases crosstalk to deteriorate signal integrity. A guard trace with a periodic structure is therefore proposed for simultaneously reducing common-mode radiation and maintaining signal integrity. Several test boards with different period patterns were evaluated by measurement and full-wave simulation from the viewpoint of transmission coefficient as well as common-mode radiation. As a result, it was found that the guard trace with the periodic structure helps reduce common-mode radiation and maintain signal integrity except for a couple of conditions.

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Suppression of noise propagation between power and ground planes using ferrite-plated EBG structure

K. Kondo, S. Yoshida, Y. Toyota

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 61 ( S1 ) S299 - S302 2014

Language：English Publisher：Journal of the Japan Society of Powder and Powder Metallurgy

To confirm the feasibility of suppressing electromagnetic interference (EMI) in the inner layers of multilayered printed wiring boards (PWBs) and sustaining power integrity characteristics, influence of inserting a ferrite-plated thin film between the power and ground planes on the transmission characteristics were evaluated using four types of test boards with the following two conditions: one is the solid test board with a plane copper foil or the EBG (Electromagnetic bandgap) test boards with a one-dimensional lattice-shaped EBG structure consisting of large and small squares 15 mm x 15 mm and 1.5 mm x 1.5 mm in size
the other is whether the 3 or 6 μm-thick ferrite film was deposited or not. The multiple peaks of the transmission coefficient S21 due to parallel plate resonances were observed in the solid test board without ferrite film but the peaks were suppressed over the wide frequency range up to 6 GHz by applying the ferrite film. The EBG test board with the ferrite film provided not only wideband attenuation owing to the ferrite film but also large attenuation in the EBG stopband. The multiple peaks of in the driving point impedance Z11 due to the parallel plate resonances were also successfully suppressed by applying the ferrite film exhibiting favorable power integrity characteristics.

DOI： 10.2497/jjspm.61.S299

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Modal-equivalent-circuit Modeling of Bend Discontinuity of Differential Transmission Lines

TOYOTA Yoshitaka, KAN Shohei, IOKIBE Kengo, WATANABE Tetsushi

IEICE technical report. Electromagnetic compatibility 113 ( 310 ) 41 - 46 2013.11

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

The bend in a differential transmission line is expressed as a modal equivalent circuit from the view of the mode-decomposition technique. Then, we investigated the relationship of the mode-conversion sources inside the bend and the neighboring reactive elements with the amount of mode conversion. It was found that not only the difference in imbalance factor but also the magnitude of the reactive elements ccan affect mode conversion.

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Application of LECCS Model to Predict on-Board Power Voltage Variation of FPGA

SHIMIZU Kana, IOKIBE Kengo, TOYOTA Yoshitaka, WATANABE Tetushi

IEICE technical report. Microwaves 113 ( 260 ) 163 - 168 2013.10

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

In this study, an equivalent circuit model of a field programmable gate array (FPGA) implemented on a commercial printed circuit board was identified. The model, called Linear Equivalent Circuit and Current Source (LECCS) model, was applied to predict the power supply voltage variations due to high-frequency current of the FPGA. The LECCS model was identified from on-board measurements. Then, the power supply voltage variation was calculated by a circuit simulation with the identified LECCS and PDN equivalent circuit model. In this study, the predictions of the power supply voltage variation were verified for 1000 input data. As a result, cross-correlation values between measured and simulated voltage waveforms were 0.8 or more for all the 1,000 input data. This means that LECCS model can predict the power supply voltage variation including input data dependency.

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Simulation of Side-Channel Attack at Board Level by Use of Equipment Circuit Model

Iokibe Kengo, Toyota Yoshitaka

Proceedings of the Society Conference of IEICE 2013 ( 1 ) "SS - 36"-"SS-37" 2013.9

Design Method of On-Board RL Snubber Inserted in Power Distribution Network of Integrated Circuits

YAMAGATA Ryosuke, IOKIBE Kengo, TOYOTA Yoshitaka

IEICE technical report. Electromagnetic compatibility 113 ( 122 ) 39 - 43 2013.7

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

The power distribution network (PDN) of modern integrated circuits (ICs) have parasitic impedances along power and ground traces, vias, and components as well as nominal impedances of the components: capacitors, voltage regulators, filters, and ICs. Such parasitic impedances, at the resonant frequency, may increase the radio frequency (RF) power current to cause conducted EM radiation and surge the PDN input impedance to induce power bounces. There is the RL snubber circuit that had been applied to a typical PDN decreasing the RF power current and descending the PDN input impedance by damping the parasitic impedance resonance. The RL snubber is composed of a parallel pair of decoupling inductor and damping resister. This report introduced a design method of the RL snubber for the parasitic impedance resonance of on-board parasitic capacitances.In the design method, the allowable range of the decoupling inductance was restricted for practical use of the method to simplify the equivalent circuit that expressed the target resonance. The simplified equivalent circuit was a 2nd order circuit whereas the original one was 3rd order.With the restricted inductance, an optimal resistance was determined in accordance with the critical damping conditions of the 2nd order circuit. Finally, the design method was evaluated on the basis of the circuit simulation calculating the current transmittance and PDN input impedance. As a result, the introduced design method was confirmed to reduce as much RF power current and power bounce as the more thetically strict way. Moreover, the method was found to be able to be more practical by relaxing the restriction on the decoupling inductance of RL snubber.

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Suppression of Power-bus Resonance Using Lossy Resonator Filter Consisting of Open Stub and Magnetic Thin Film

TOYOTA Yoshitaka, IOKIBE Kengo, KONDO Koichi, YOSHIDA Shigeyoshi

IEICE technical report. Electromagnetic compatibility 113 ( 25 ) 25 - 30 2013.5

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

Power-bus resonance of printed circuit board (PCB) causes propagation of electromagnetic noise and detraction of power integrity. For suppressing the power-bus resonance, the following two aspects are important: suppression of power-bus resonances focusing only on each specific resonance; reduction of the resonant energy stored between the power and ground planes. In this paper, we propose a lossy resonator filter consisting of an open stub covered with a magnetic thin film. This paper first explains the concepts of the proposed filter, especially focusing on the impedance characteristics, and then demonstrates that the proposed filter suppress power-bus resonances effectively by full-wave simulation.

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Quantitative estimation of total EMI radiation with normal-mode and common-mode antenna models

WATANABE Tetsushi, WAKADUKI Yuri, TOYOTA Yoshitaka, IOKIBE Kengo

IEICE technical report. Electromagnetic compatibility 113 ( 2 ) 7 - 12 2013.4

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

The currents of two modes, normal mode and common mode flow along two-conductor lines placed in the air. We have so far developed the prediction method of common-mode current and radiation in a printed circuit board focusing on the imbalance of the transmission line. The difference of the imbalances causes the mode conversion, from normal mode to common mode. In this paper, it is examined that the vector sum of common-mode radiation and normal-mode radiation should be equal to total radiation. Each modal radiation is calculated separately with the corresponding equivalent model. The modeling method is applied to three kinds of printed-circuit-board structures. It is validated that the far electric field from the real-structure model agrees with the vector sum of far electric fields from normal-mode and common-mode equivalent models.

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Reduction in Common-mode Radiation and Maintenance of Signal Integrity by Adding Guard Trace with Periodic Structure

TERAI Yuho, TOYOTA Yoshitaka, IOKIBE Kengo, WATANABE Tetsushi

IEICE technical report. Electromagnetic compatibility 113 ( 2 ) 1 - 6 2013.4

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

The guard trace is effective as a method for suppressing common-mode generation caused by placing a signal trace close to the return edge on a printed circuit board. Our previous study on the guard trace focused only on reducing common-mode radiation, but the guard trace close to the signal line increases crosstalk to deteriorate signal integrity. In this paper, we propose a guard trace with a periodic structure for simultaneously reducing common-mode radiation and maintaining signal integrity. Several test boards with different period patterns were evaluated by measurement and simulation from the viewpoint of transmission coefficient, eye pattern, and common-mode radiation. As a result, it was found that the guard trace with the periodic structure helped reducing common-mode radiation and maintaining signal integrity. Especially, smaller period contributed to maintenance of signal integrity at higher frequencies.

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Noise Investigation of Cryptographic ICs for Side-Channel Analysis by Means of Equivalent Current Source Model : A Study with SASEBO-G

IOKIBE Kengo, AMANO Tetsuo, TOYOTA Yoshitaka, WATANABE Tetsushi

IEICE technical report. Electromagnetic compatibility 113 ( 2 ) 25 - 30 2013.4

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

It is an important issue to predict noise in cryptographic integrated circuits (ICs) in developing security design methodologies against side-channel analysis attacks, because the noise prediction can affect the reliability of safety estimation of cryptographic devices against side-channel analysis attacks. The noise in cryptographic ICs varies during an encryption operation and is difficult to be identified from measurements. The noise variation was investigated by means of the equivalent current source model of a cryptographic FPGA that the authors determined in their previous studies. Standard deviations of the noise was calculated for a couple of plaintexts of the Advanced Encryption Standard (AES) with a 128-bit key. The standard deviations were found positively correlated with the magnitude of the equivalent current source.

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B-4-58 Identification of Equivalent Current Source of Cryptographic FPGA for Side-Channel Attack Simulations

Iokibe Kengo, Okamoto Kaoru, Amano Tetsuo, Toyota Yoshitaka, Watanabe Tetsushi

Proceedings of the IEICE General Conference 2013 ( 1 ) 403 - 403 2013.3

B-4-36 Relationship of Mode Conversion with lmbalance Factor and Voltage Reflection Coefficient

NOBUNAGA Tatsuya, TOYOTA Yoshitaka, IOKIBE Kengo, KOGA Liuji R., WATANABE Tetsushi

Proceedings of the IEICE General Conference 2013 ( 1 ) 381 - 381 2013.3

Optimization of Resistances in RL Snubbers for Power Distribution Network of Integrated Circuits

Ryosuke Yamagata, Kengo Iokibe, Yoshitaka Toyota

Proceedings of 2013 International Symposium on Electromagnetic Theory (EMTS 2013) 226 - 229 2013

Equivalent circuit modeling of cryptographic integrated circuit for information security design

Kengo Iokibe, Tetsuo Amano, Kaoru Okamoto, Yoshitaka Toyota

IEEE Transactions on Electromagnetic Compatibility 55 ( 3 ) 581 - 588 2013

Language：English

In this study, equivalent circuit modeling was examined to develop a method to evaluate cryptographic systems before fabrication. An equivalent circuit model of a cryptographic FPGA in which an advanced encryption standard (AES) algorithm had been implemented was determined from experimental measurements under the initial configuration of a power distribution network (PDN) of the FPGA. The model was implemented into a commercial analog circuit simulator, and power traces due to the simultaneous switching noise current were estimated under three different PDN configurations in which a decoupling circuit was inserted into the PDN as an on-board countermeasure. Estimated power traces were analyzed statistically by the correlation power analysis method to obtain correlation values, a major security index of AES. Variation of the correlation values with changes in decoupling configuration agreed with the corresponding experimental results. This means that the security of cryptographic devices against side-channel attacks can be evaluated by using the equivalent circuit model before fabrication. © 1964-2012 IEEE.

DOI： 10.1109/TEMC.2013.2250505

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Evaluation of Pigtail Termination of STP cable Using Modal Equivalent Circuit of Four-conductor Transmission Systems

Tatsuya Nobunaga, Yoshitaka Toyota, Kengo Iokibe, Liuji R. Koga, Tetsushi Watanabe

PROCEEDINGS OF 2013 URSI INTERNATIONAL SYMPOSIUM ON ELECTROMAGNETIC THEORY (EMTS) 222 - 225 2013

Language：English Publisher：IEEE

For investigating mode conversion in four-conductor transmission systems we have developed a modal-equivalent-circuit expressed by an imbalance factor of transmission line, a current division factor, in the same way as we developed the one in three-conductor transmission systems. The modal equivalent circuit consists of three modal equivalent circuits of normal mode, primary-common mode, and secondary-common mode. In this paper, the influence of mode conversion by the pigtail termination of a shielded-twisted-pair (STP) cable was analyzed using the modal equivalent circuit and mixed-mode S parameters with respect to normal mode and primary- common mode. As a result, it was found that mode conversion depends on the imbalance factor and that the modal equivalent circuit helps to explain mode conversion that occurs in terminating STP cables with pigtail.

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RF Noise Suppression by Lossy Filters in Power Distribution Network

Yoshitaka Toyota, Kengo Iokibe

Proceedings of IEEE CPMT Symposium Japan (ICSJ 2013) 2013

Effect of EBG structure and ferrite film on power/ground layers for performance maintenance and noise suppression in wireless communication

Kenta Ishimura, Yoshitaka Toyota, Kengo Iokibe, Koichi Kondo, Shigeyoshi Yoshida

EDAPS 2013 - 2013 IEEE Electrical Design of Advanced Packaging Systems Symposium 217 - 220 2013

Language：English

Noise suppression and power integrity are two requirements for power/ground layers of printed circuit boards. To accomplish the requirements, we proposed the application of electromagnetic bandgap (EBG) structure and ferrite film to power/ground layers. To evaluate the proposed EBG structure, we have so far measured the electric characteristics of both driving-point impedance and transmission coefficient. Although these evaluation indices are helpful, the evaluation using an actual device is also indispensable. In this paper, we evaluated the suppression of noise propagation through power bus by the proposed EBG structure in wireless communication module. The proposed structure provided sufficient result of the effective maintenance of communication quality by suppressing the propagation of electromagnetic noise. © 2013 IEEE.

DOI： 10.1109/EDAPS.2013.6724428

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