• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.1997-2003
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• 2003

Recently, there have been many researches and developments in optical disc drive by high density of track and high access speed. Therefore, the optical pick-up should guarantee highly accurate dynamic characteristics for the wide bandwidth in order to cope with this trend. These demands for optical pick-up actuator can be solved by improvements of lens-holder through the following methods. The first way is the analysis of the sensitivity matrix of design variables for vibration modes after appropriate design parameters are selected like shapes and local dimensions of a lens-holder. The second way is the optimization of design variables by calculating sequential linear programming after the problem of extending bandwidth are converted to problem of minimizing adequate objective function. In the result, modified FE model is obtained through several iterations by finite difference scheme(FDS). While results of the first way show better convergence of the target frequency, the second result shows better reduction of mass increase.

• The Journal of the Acoustical Society of Korea
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• v.13 no.5
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• pp.77-82
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• 1994

In speech signal processing, it is very important to detect the pitch exactly. Although various methods for detecting the pitch of speech signals have been developed, it is difficult to exactly extract the pitch for wide range of speakers and various utterances. Thus we propose a new pitch detection algorithm which takes advantage of the G-peak extraction. It is a method to detect the pitch period of the voiced signals by finding MZCI (maximum zero-crossing interval) of the G-peak which is defined as cut-off bandwidth rate of LPF (low pass filter). This algorithm performs robustly with a gross error rate of 3.63% even in 0 dB SNR environement. The gross error rate for clean speech is only 0.18%. Also it is able to process all courses with high speed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.51-56
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• 2008

In this paper, we propose a printed planar antenna suitable for mobile wireless communications. Since the printed antenna is easy to fabricate due to simplicity, low cost, and light weight, it is widely used in communications systems. The conventional patch antenna takes too much surface area to be applied to a mobile receiver. Although the size is reduced using the printed antenna, still reasonably wide bandwidth should be considered. To overcome the disadvantage of narrow bandwidth, the substrate should be physically thick and the dielectric constant should be small. In this work, we suggest a simple form of printed planar antenna and show the optimal input impedance depending on the antenna size and operating frequency. The performance evaluation is achieved analytically for a prototype antenna model.

• Journal of IKEEE
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• v.22 no.3
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• pp.599-604
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• 2018

A Stepped Frequency Radar(SFR) is a method that realizes high resolution range estimation by increasing the frequency of transmission pulses at regular intervals to generate a wide synthetic bandwidth. However, in the case of a moving target, accurate range estimation becomes difficult due to the range-Doppler coupling. In this paper, the process of high resolution range estimation by compensation of the range-Doppler coupling with estimated velocity of the moving target using the SFR waveform with Coherent Pulse Train(CPT) is analyzed and it was verified through simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.33-38
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• 2012

In this paper, helical wave wire have been proposed as the vehicle connector for the wireless access in vehicular environments(5.925GHz) communication. This helical slow wave connector is design by considering the properties of critical parameter like helical mean radius, helical pitch, helical wire radius and distance of helical wire to shield. The design simulation and results can be used to determine the most suitable helical wave wire dimensions for vehicle communication connector. The optimized WAVE connector inserted the helical wave wire has insertion loss less than -0.76dB at 5.925GHz. It provides 31% of insertion loss with good performance. Therefore, the simulated results can be effectively used for optimum design of high frequency connector for vehicle communication.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.177-178
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• 2014

This work proposes a two-dimensional (2-D) laser scanning mirror actuator with a simple structure composed of one magnet and four coils. The mirror-actuating device generates 2-D scanning motions about two orthogonal axes by combining electromagnetic actuators of the conventional moving-magnet types. The magnet is attached to back side of the mirror placed inside of the moving frame. The four coils is placed on the base frame in a cross shape. We implement a finite element analysis to calculate magnetic flux in the electromagnetic system with the overall size of $20mm(W){\times}20mm(D){\times}13mm(H)$ for the mirror size of $8mm{\times}8mm$. The each moving-magnet type electromagnetic actuator has the motor constant 3.41 mNm/A and the restoring constant 1.75 mNm/rad and the resonance frequency of 58 Hz and the bandwidth of 80 Hz. The proposed compact and simple 2-D scanning mirror predicted advantages of large 2-D angular deflections, wide frequency bandwidth and low manufacturing cost.

• Journal of Sensor Science and Technology
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• v.4 no.1
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• pp.15-20
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• 1995

This paper deals with the planar-type sensor which can measure the time-varying electric fields. To make an electric field measurement system having a wide bandwidth, a planar-type sensor is proposed. The theoretical principle and design rule of the measuring device are introduced, and also the calibration and application investigations are carried out. From the calibration experiments, the frequency bandwidth of the electric field measurement device ranges from 160 [Hz] to 25 [MHz] and the sensitivity of the sensor is 1.2 [mV/V/m]. As the application experiments, the electric fields caused by the impulse and oscillating transient voltage in high voltage laboratory are measured by the proposed device, and the results are excellent.

• Smart Media Journal
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• v.4 no.4
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• pp.64-69
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• 2015

In this paper, we have proposed a tapered slot antenna for UWB communication system. The tapered slot antenna has directional radiation and broad bandwidth. Proposed tapered slot antenna is designed using Ansys Inc. HFSS and its VSWR, return los, and radiation pattern is analyzed. Operating band of the antenna were satisfied -10 dB S11 and $VSWR{\leq}2$ in 2.7 ~ 4.8 GHz band. The radiation pattern of the antenna is showed in E-plane (YZ plane) and the H-plane (XZ plane) and the highest gain of 7.3 dBi is seen at 4.5 GHz. Therefore, proposed tapered slot antenna has wide bandwidth characteristic and directional for location awareness.

• ETRI Journal
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• v.31 no.6
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• pp.749-754
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• 2009

The design and performance of an InGaAs/InP transimpedance amplifier and post amplifier for 40 Gb/s receiver applications are presented. We fabricated the 40 Gb/s transimpedance amplifier and post amplifier using InGaAs/InP heterojunction bipolar transistor (HBT) technology. The developed InGaAs/InP HBTs show a cut-off frequency ($f_T$) of 129 GHz and a maximum oscillation frequency ($f_{max}$) of 175 GHz. The developed transimpedance amplifier provides a bandwidth of 33.5 GHz and a gain of 40.1 $dB{\Omega}$. A 40 Gb/s data clean eye with 146 mV amplitude of the transimpedance amplifier module is achieved. The fabricated post amplifier demonstrates a very wide bandwidth of 36 GHz and a gain of 20.2 dB. The post-amplifier module was fabricated using a Teflon PCB substrate and shows a good eye opening and an output voltage swing above 520 mV.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.83-84
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• 2016

A wideband stacked patch antenna with parasitic elements, rectangular and triangle shaped patches, is proposed. Two different shaped parasitic elements are placed in the above of main rectangular microstrip patch antenna in order to achieve wide bandwidth for 860 MHz band. Coupling between the main patch and parasitic patches is realized by thick air gap. The gap and locations of parasitic patches are found to be the main factor of the wideband impedance matching. The proposed antenna is designed on a ground plane with small size of $119mm{\times}109mm$ for application of compact transceivers. And the impedance bandwidth of the antenna should satisfied CDMA band to the 780MHz~890MHz.