• Journal of Power Electronics
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• v.19 no.5
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• pp.1303-1314
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• 2019

This paper studies the harmonic characteristics of ship electric propulsion systems and their treatment methods. It also adopts effective measures to suppress and prevent ship power systems from affecting ship operation due to the serious damage caused by harmonics. Firstly, the harmonic characteristics of a ship electric propulsion system are reviewed and discussed. Secondly, aiming at problems such as resonant frequency and filter characteristics variations, resonance point migration, and unstable filtering performances in conventional passive filters, a method for fully tuning of a passive dynamic tunable filter (PDTF) is proposed to realize harmonic suppression. Thirdly, to address the problems of the uncontrollable inductance L of traditional air gap iron core reactors and the harmonics of power electronic impedance converters (PEICs), this paper proposes an electromagnetic coupling reactor with impedance transformation and harmonic suppression characteristics (ECRITHS), with the internal filter (IF) designed to suppress the harmonics generated by PEICs. The ECRITHS is characterized by both harmonic suppression and impedance change. Fourthly, the ECRITHS is investigated. This investigation includes the harmonic suppression characteristics and impedance transformation characteristics of the ECRITHS at the fundamental frequency, which shows the good performance of the ECRITHS. Simulation and experimental evaluations of the PDTF are carried out. Multiple PDTFs can be configured to realize multi-order simultaneous dynamic filtering, and can effectively eliminate the current harmonics of ship electric propulsion systems. This is done to reduce the total harmonic distortion (THD) of the supply currents to well below the 5% limit imposed by the IEEE-519 standard. The PDTF also can eliminate harmonic currents in different geographic places by using a low voltage distribution system. Finally, a detailed discussion is presented, with challenges and future implications discussed. The research results are intended to effectively eliminate the harmonics of ship electric power propulsion systems and to improve the power quality of ship power systems. This is of theoretical and practical significance for improving the power quality and power savings of ship power systems.

• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.59-66
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• 2010

In this paper, the internal antenna for mobile communication handset which is able to control both coupling coefficient and resonant frequency without any major modification of radiator and ground plane of antenna. Novel internal antenna with its controllable resonant frequency is presented for triple-band or over mobile handsets. The operating range can include GSM(880~960 MHz), GPS($1,575{\pm}10MHz$), DCS(1,710~1,880MHz), US-PCS(1,850~1,990 MHz), and W-CDMA(1,920~2,170 MHz). The proposed antenna is realized by combination of a half wavelength loaded line antenna and PIFA(Planner Inverted F Antenna). A single shorting and feeding points are used and they are common to both antenna structures. One of two inductors which is placed at each shorting post, one inductor is for adjusts amount of coupling, and the other controlling the resonant frequency in DCS/US-PCS/WCDMA bands. The inductance range for control of input impedance is between 0nH and 6.8nH, and each of gain variation in GSM, GPS and DCS/US-PCS/WCDMA band is under 0.15dBi, 0.73dBi and 0.29dBi. The inductance range for control of the resonant frequency is between 1640MHz and 2500MHz, and each of gain variation in GSM, GPS and DCS/US-PCS/WCDMA band is under 0.46dBi, 0.53dBi and 0.8dBi.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.140-145
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• 2002

We measured the absorption rate of a Nd:YVO$_4$crystal with a thickness of 1 mm and the output power characteristics of a cw Nd:YVO$_4$/KTP laser with respect to the change of wavelength and the polarizations of a tunable Ti:sapphire pump laser with a linewidth of 0.2 nm. In the case of S-polarization (E┴$\pi$) and P-polarization (E∥$\pi$) of a pump laser, the maximum absorption rate of the crystal was 82% at 809.4 nm and 98% at 808.8 nm, and slope efficiencies for the output power of the Nd:YVO$_4$laser (1064 nm) were 43% and 52%, respectively. The maximum Nd:YYO$_4$laser output power of 516 mW was obtained from the P-polarization pump laser of 1000 mW. As a result of an intracavity frequency-doubling, slope efficiency for the output power of the Nd:YVO$_4$/KTP green laker (532nm) was 23% and the maximum output power of 205 mW with the beam quality (M$^2$) of 1.42 was obtained from the P-polarization pump laser of 1000 mW.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.5
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• pp.27-37
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• 1999

A CMOS ReadOut Integrated Circuit (ROlC) for InfraRed Focal Plane Array (IRFPA) detector is presented, which is a key component in uncooled thermal imaging systems. The ROIC reads out signals from $64\times64$ Barium Strontium Titanate (BST) infrared detector array, then outputs pixel signals sequentially after amplifying and noise filtering. Various design requirements and constraints have been considered including impedance matching, low noise, low power dissipation and small detector pitch. For impedance matching between detector and pre~amplifier, a new circuit based on MOS diode structure is devised, which can be easily implemented using standard CMOS process. Also, tunable low pass filter with single~pole is used to suppress high frequency noise. In additions, a clamping circuit is adopted to enhance the signal~to-noise ratio of the readout output signals. The $64\times64$ IRFPA ROIC is designed using $0.65-\mu\textrm{m}$ 2P3M (double poly, tripple metal) N~Well CMOS process. The core part of the chip contains 62,000 devices including transistors, capacitors and resistors on an area of about $6.3-mm\times6.7-mm$.

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.22-27
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• 2017

Time-encoded near-infrared spectroscopy (NIRS) system is proposed, based on a near-infrared (NIR) swept laser source, for comparison to the conventional NIRS method using a detector-type spectrometer. The cavity of the NIR swept laser source consists of a semiconductor optical amplifier (SOA) with a gain region around 800 nm, and several fiber-optic components. To change the output wavelength in time using an applied electric radio-frequency signal, an acousto-optic tunable filter (AOTF) is introduced in the fiber ring cavity configuration. To demonstrate the feasibility of an NIR swept laser source for NIRS imaging, the spectroscopic comparison of two kinds of absorbance-measuring systems a detector-type spectrometer using a white light source, and a source-type spectrometer using an NIR swept laser is successfully performed with an NIR-absorbing dye.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.2
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• pp.50-55
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• 2008

In this paper, multi-band internal antenna which can adjust both resonant frequency and input impedance of antenna as using lumped inductor between shoring plate and ground plane is proposed. The structure of proposed antenna consists of PIFA (Planar Inverted F Antenna) structure and half-wavelength loaded line structure and has two shorting plates and one feeding plate. One shorting plate is shared. The operating frequency bands of designed antenna are GSM, GPS in the PIFA structure and DCS, US-PCS, W-CDMA in half-wave loaded line structure as varying the inductor value in 2.2nH, 3.3nH, and 4.7nH. As varying the inductor value in the shared shorting plate, input impedance of antenna is varied. To minimize the gain variation of antenna as adding lumped element, the inductor value is restricted at maximum of 6.8nH. The maximum gain of proposed antenna is measured as -1.60dBi in the GSM band, -1.16dBi in the GPS band, and 1.41dBi in the DCS/US-PCS/W-CDMA band.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.253-263
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• 2013

Frequency Scanning Interferometry(FSI) system, one of the most promising optical surface measurement techniques, generally results in superior optical performance comparing with other 3-dimensional measuring methods as its hardware structure is fixed in operation and only the light frequency is scanned in a specific spectral band without vertical scanning of the target surface or the objective lens. FSI system collects a set of images of interference fringe by changing the frequency of light source. After that, it transforms intensity data of acquired image into frequency information, and calculates the height profile of target objects with the help of frequency analysis based on Fast Fourier Transform(FFT). However, it still suffers from optical noise on target surfaces and relatively long processing time due to the number of images acquired in frequency scanning phase. 1) a Polarization-based Frequency Scanning Interferometry(PFSI) is proposed for optical noise robustness. It consists of tunable laser for light source, ${\lambda}/4$ plate in front of reference mirror, ${\lambda}/4$ plate in front of target object, polarizing beam splitter, polarizer in front of image sensor, polarizer in front of the fiber coupled light source, ${\lambda}/2$ plate between PBS and polarizer of the light source. Using the proposed system, we can solve the problem of fringe image with low contrast by using polarization technique. Also, we can control light distribution of object beam and reference beam. 2) the signal processing acceleration method is proposed for PFSI, based on parallel processing architecture, which consists of parallel processing hardware and software such as Graphic Processing Unit(GPU) and Compute Unified Device Architecture(CUDA). As a result, the processing time reaches into tact time level of real-time processing. Finally, the proposed system is evaluated in terms of accuracy and processing speed through a series of experiment and the obtained results show the effectiveness of the proposed system and method.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.361.1-361.1
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• 2016

Due to their high sensitivity, fast response, small energy consumption and ease of integration, nanoelectromechanical systems (NEMS) have attracted much interest in various applications such as high speed memory devices, energy harvesting devices, frequency tunable RF receivers, and ultra sensitive mass sensors. Since the device performance of NEMS is closely related with the mechanical and flexural properties of the material in NEMS, analysis of the mechanical and flexural properties such as intrinsic tensile stress and Young's modulus is a crucial factor for designing the NEMS structures. In the present work, the intrinsic mechanical properties of highly stressed silicon nitride (SiN) beams are investigated as a function of the beam length using two different techniques: (i) dynamic flexural measurement using optical interferometry and (ii) quasi-static flexural measurement using atomic force microscopy. The reliability of the results is analysed by comparing the results from the two different measurement techniques. In addition, the mass density, Young's modulus and internal stress of the SiN beams are estimated by combining the techniques, and the prospect of SiN based NEMS for application in high sensitive mass sensors is discussed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.1
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• pp.129-140
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• 2017

In this paper, a $4{\times}32$-channel neural recording system capable of acquiring neural signals is introduced. Four 32-channel neural recording ICs, complex programmable logic devices (CPLDs), a micro controller unit (MCU) with USB interface, and a PC are used. Each neural recording IC, implemented in $0.18{\mu}m$ CMOS technology, includes 32 channels of analog front-ends (AFEs), a 32-to-1 analog multiplexer, and an analog-to-digital converter (ADC). The mid-band gain of the AFE is adjustable in four steps, and have a tunable bandwidth. The AFE has a mid-band gain of 54.5 dB to 65.7 dB and a bandwidth of 35.3 Hz to 5.8 kHz. The high-pass cutoff frequency of the AFE varies from 18.6 Hz to 154.7 Hz. The input-referred noise (IRN) of the AFE is $10.2{\mu}V_{rms}$. A high-resolution, low-power ADC with a high conversion speed achieves a signal-to-noise and distortion ratio (SNDR) of 50.63 dB and a spurious-free dynamic range (SFDR) of 63.88 dB, at a sampling-rate of 2.5 MS/s. The effectiveness of our neural recording system is validated in in-vivo recording of the primary somatosensory cortex of a rat.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.506-513
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• 2015

In this paper, we proposed a novel ethanol concentration sensor using microfluidic metamaterial absorber. The metamaterial absorber comprises a split-ring-cross resonator(SRCR) and a microfluidic channel. The SRCR can generate LC resonance that is very sensitive to changes in the effective dielectric constant around the capacitive gap. In addition, microfluidic channels can change the effective dielectric constant of the dielectric substrate by using an infinitesimal quantity of a liquid on the order of microliters. The proposed absorber can detect the electrical properties of different concentration of ethanol. The performance of the proposed absorber is demonstrated using the absorption measurements of a fabricated prototype sample with waveguides. In addition, the simulated results and measurement results show good agreement.