Showing 1-25 of 141 resultsfor "Authors":"K. Sasagawa"
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We have realized for the first time a heterodyne system of fairly large scale parallelism, which enables instantaneous photonic acquisition of electromagnetic near-field images over microwave devices/circuits at a specific radio frequency. It has been demonstrated that a pair of intensity and phase images of 10,000 pixels are acquired in 1 second or shorter for in-plane electric field distribution...Show More
High efficiency third harmonic generation in PPMgLN disk resonator
2007 Conference on Lasers and Electro-Optics (CLEO)
Year: 2007 | Conference Paper |
Cited by: Papers (1)
DC voltage control strategy for a five-level converter
This paper describes a control method for a three-phase five-level diode-clamp pulse width modulation (PWM) converter considering DC-link capacitor voltage balancing problem. The proposed control circuit uses multiband hysteresis comparators (MHCs) to simplify the control of the main circuit. The DC-link capacitor voltage balancing problem is solved by changing the shape of the MHC. The proposed m...Show More
Sensorless control of direct-field-oriented induction motor operating at high efficiency using adaptive rotor flux observer
Proceedings of the 1996 IEEE IECON. 22nd International Conference on Industrial Electronics, Control, and Instrumentation
Year: 1996 | Conference Paper |
Cited by: Papers (15)
The speed sensorless control of direct-field-oriented induction motors using an adaptive rotor flux observer was developed recently. This method drives the induction motor using a constant-rated rotor flux in order to estimate rotor speed without loss of accuracy and to prevent degeneration of dynamic response. However, the driving efficiency of the field-oriented induction motor must be maximized...Show More
Sensorless control of direct-field-oriented induction motor operating at high efficiency using adaptive rotor flux observer
Year: 1996 | Conference Paper |
DC voltage control strategy for a five-level converter
APEC '99. Fourteenth Annual Applied Power Electronics Conference and Exposition. 1999 Conference Proceedings (Cat. No.99CH36285)
Year: 1999 | Conference Paper |
Cited by: Papers (4)
This paper describes a control method for a diode-clamped three-phase five-level PWM power converter considering the DC-link capacitor balancing problem. The proposed control circuit uses multiband hysteresis comparators (MHCs) to simplify the control of the main circuit. The DC-link capacitor balancing problem is solved by changing the shape of the MHC. The proposed method can: (1) overcome volta...Show More
Charge-Pump-Circuit Implementation for Increasing Sink Current in Low-Voltage CMOS Retinal-Prosthesis Chips
Wisaroot Sriitsaranusorn;Yuki Nakanishi;Takaya Hattori;Kuang-Chih Tso;Kenzo Shodo;Hironari Takehara;Yoshinori Sunaga;Makito Haruta;Hiroyuki Tashiro;Yasuo Terasawa;Jun Ohta;Kiyotaka Sasagawa
2024 IEEE Asia Pacific Conference on Circuits and Systems (APCCAS)
Year: 2024 | Conference Paper |
Constant-current-mode, retinal-prosthesis chips require a high-voltage range to counteract the ohmic drop. To increase the sink-current capability of the chip, the voltage of the counter electrode was increased from 5 V to 7.5 V while maintaining the chip supply voltage at 5 V. This work demonstrates the implementation of a simple charge-pump circuit to handle the forward-bias current in the p-cha...Show More
Charge-Pump-Circuit Implementation for Increasing Sink Current in Low-Voltage CMOS Retinal-Prosthesis Chips
Wisaroot Sriitsaranusorn;Yuki Nakanishi;Takaya Hattori;Kuang-Chih Tso;Kenzo Shodo;Hironari Takehara;Yoshinori Sunaga;Makito Haruta;Hiroyuki Tashiro;Yasuo Terasawa;Jun Ohta;Kiyotaka Sasagawa
Year: 2024 | Conference Paper |
Needle-Type Imager Sensor With Band-Pass Composite Emission Filter and Parallel Fiber-Coupled Laser Excitation
Erus Rustami;Kiyotaka Sasagawa;Kenji Sugie;Yasumi Ohta;Makito Haruta;Toshihiko Noda;Takashi Tokuda;Jun Ohta
This paper presents an implantable fluorescence system with a composite emission filter and fiber-coupled laser excitation. The composite structure of the short-pass interference filter and absorption filters exhibited a band-pass spectrum between 510 and 570 nm, which is close to green fluorescent protein (GFP) emission. A high-quality excitation light was achieved by utilizing a blue laser throu...Show More
A novel commutation method of matrix converter fed induction motor drive using RB-IGBT
Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005.
Year: 2005 | Conference Paper |
Cited by: Papers (5)
A 3-phase to 3-phase matrix converter is developed based on 600 V/100 A RB-IGBT (Reverse Blocking IGBT). This RB-IGBT is newly developed based on ultra-thin wafer technology and one important feature of it is reverse leakage current is mostly affected by Vge. Under the same temperature condition, when Vce is negative, a positively biased Vge leads to the great reduction of the reverse leakage curr...Show More
Proposal and evaluation of intra-body sensing via sheet medium
Takashi Matsuda;Bing Zhang;Keren Li;Kiyotaka Sasagawa;Jun Ohta;Peter Davis
2012 Ninth International Conference on Networked Sensing (INSS)
Year: 2012 | Conference Paper |
Cited by: Papers (1)
In recent years, Intra-Body Communication (IBC) has attracted attention as a key new technique for health monitoring. It is expected that health monitoring can be improved by embedding sensors inside of the body. Then, the technology for communication between embedded sensors and monitoring systems outside of the body becomes important. Wireless communication is preferred to avoid the invasiveness...Show More
This paper presents a new method for balancing voltages of series-connected insulated gate bipolar transistors (IGBTs). This method can be implemented only by adding simple circuits to the gate drive system of the IGBTs, and its effect of balancing the IGBT's collector-emitter voltages during the switching transients is remarkable. This principal strategy and experimental results with series-conne...Show More
Live Electrooptic Imaging of $W$-Band Waves
Masahiro Tsuchiya;Kiyotaka Sasagawa;Atsushi Kanno;Takahiro Shiozawa
A novel method for real-time visual observation of traveling -band waves is described. Wave images and movies are acquired by a live electrooptic imaging (LEI) camera equipped with an optical source that emits signals modulated at a local oscillator (LO) frequency in the -band range. Waves propagating in a slab waveguide made of a semiconductor plate as well as in the air are successfully visualiz...Show More
Evaluation of threshold current density of electromigration damage considering passivation thickness
2016 International Conference on Advances in Electrical, Electronic and Systems Engineering (ICAEES)
Year: 2016 | Conference Paper |
Cited by: Papers (1)
Many types of micro-nanoscaled integrated circuits are designed and used in electronics fields. However they are often used without ensuring high reliability. Electromigration which is an atomic transportation phenomena due to high electric current density applied in metal lines is a critical problem in integrated circuits reliability. The passivated metal line has a threshold current density of e...Show More
A novel driving and protection circuit for reverse blocking IGBT used in matrix converter
Zhichao Liu;Daning Zhou;Kai Sun;Lipei Huang;K. Matsuse;K. Sasagawa
Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting.
Year: 2004 | Conference Paper |
Cited by: Papers (1)
Reverse blocking IGBT (RB-IGBT), with the capability of blocking both forward and reverse voltage, is now receiving widely attention in power converter applications. In this paper, by introducing two dynamical current sources, a three-stage driving circuit is designed for RB-IGBT to reduce the switching transition while limiting the turn-on di/dt and the turn-off dv/dt within the safe area. Furthe...Show More
A Novel Driving and Protection Circuit for Reverse-Blocking IGBT Used in Matrix Converter
Daning Zhou;Kai Sun;Zhichao Liu;Lipei Huang;Kouki Matsuse;Kiyoaki Sasagawa
A novel drive and protection circuit for reverse-blocking insulated gate bipolar transistor (RB-IGBT) is proposed in this paper. For the drive circuit, a dynamic current source is introduced to reduce the turn-on and turn-off transients. Meanwhile, the di/dt of the collector current and the dv/dt of the collector-emitter voltage are strictly restricted, so do the respective stresses. The drive cir...Show More
An Implantable CMOS Image Sensor With Self-Reset Pixels for Functional Brain Imaging
Kiyotaka Sasagawa;Takahiro Yamaguchi;Makito Haruta;Yoshinori Sunaga;Hironari Takehara;Hiroaki Takehara;Toshihiko Noda;Takashi Tokuda;Jun Ohta
In this paper, we propose and demonstrate an implantable CMOS image sensor with self-resetting pixels. The self-resetting function is implemented using a four-transistor Schmitt trigger inverter. The pixel has no counter for the number of self-resets, because the application does not require radiometric (linear) response. The pixel is fabricated using the 0.35-μm 2-poly 4-metal standard CMOS techn...Show More
Polarization Image Sensor for Highly Sensitive Polarization Modulation Imaging Based on Stacked Polarizers
Kiyotaka Sasagawa;Ryoma Okada;Makito Haruta;Hironari Takehara;Hiroyuki Tashiro;Jun Ohta
In this article, We demonstrated an image sensor for detecting changes in polarization with high sensitivity. For this purpose, we constructed an optical system with a two-layer structure, comprising an external polarizer and polarizers on a pixel array. An external polarizer is used to enhance the polarization rotation while reducing the intensity to avoid pixel saturation of the image sensor. Us...Show More
Low-Noise and High-Frequency Resolution Electrooptic Sensing of RF Near-Fields Using an External Optical Modulator
Journal of Lightwave Technology
Cited by: Papers (15)
We developed an electrooptic (EO) sensing system using an external optical intensity modulator for radio frequency (RF) electric near-field measurements. This low-noise, high-frequency resolution system is based on the photonic heterodyning technique in which a RF near-field signal is mixed with modulated light by an EO crystal and downconverted to the difference frequency. Because the optical mod...Show More
Demonstration of implantable CMOS image sensors for functional brain imaging
Kiyotaka Sasagawa;Yoshinori Sunaga;Makito Haruta;Takahiro Yamaguchi;Hironari Takehara;Hiroaki Takehara;Toshihiko Noda;Takashi Tokuda;Jun Ohta
2014 IEEE Biomedical Circuits and Systems Conference (BioCAS) Proceedings
Year: 2014 | Conference Paper |
Cited by: Papers (1)
We have developed implantable complementary -metal-oxide-semiconductor (CMOS) imaging devices for brain functional imaging (Fig.1) [1]. With the device, it is possible to perform fluorescence or absorption imaging and observe various neural activities of the mouse brain in a freely moving state [2, 3]. The device comprises a CMOS image sensor, and LEDs as excitation or illumination light sources. ...Show More
Battery-Free. Sticker-Like, Device for Health Monitoring, Operated by Optical Power Transfer
Nattakam Wuthibenjaphonchai;Makito Haruta;Toshihiko Noda;Kivotaka Sasagawa;Takashi Tokuda;Mohamad Sawan;Sandro Carrara;Jun Ohta
2018 IEEE Biomedical Circuits and Systems Conference (BioCAS)
Year: 2018 | Conference Paper |
Cited by: Papers (1)
This work presents the concept of a battery-free, sticker-like, device for a non-invasive health-monitoring sensor. The device consists of two functional blocks: an optical power-transfer block and an amperometric measurement block. The former accumulates power from a series-connected photovoltaic cell in a capacitor and intermittently supplies the power to the amperometric measurement circuit. Th...Show More
10-GHz Imaging by an Electro-Optic Imaging System Based on Polarization CMOS Image Sensor
Ryoma Okada;Kiyotaka Sasagawa;Maya Mizuno;Hironari Takehara;Makito Haruta;Hiroyuki Tashiro;Jun Ohta
2022 IEEE Photonics Conference (IPC)
Year: 2022 | Conference Paper |
In this study, we demonstrate an electro-optic (EO) imaging system for 10 GHz. By using an optical modulator and an optical amplifier, we generated a high-frequency optical local oscillator signal. Amplitude and phase distribution images of microwave electric fields were imaged by the proposed system.Show More
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