• Journal of the Institute of Convergence Signal Processing
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• v.4 no.1
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• pp.49-55
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• 2003

The use of digital filters in the signal process field is increasing rapidly with development of the modern industrial society. Especially, detail processors, Y/C separators, ghost removing filters, standard converters (NTSC to PAL or PAL to NTSC) and noise reducers, all of which use digital filters, tend to be used in digital video and audio processing, CATV and various communication fields. Generally, there are two different digital filters, the Rf (infinite impulse response) filter and the FIR (finite impulse response) filter in digital filter. In this paper, we have designed FIR filter which has the phase linearity and the easiness of creation. In the design of the FIR digital filter, the window function is used to alleviate the ripples caused by Gibbs Phenomenon around the cut off frequency of the band pass. But there're some problems to choose proper window function for the design destination due to its fixed values. Therefore, in this paper, we designed a modified Hanning window with new parameter which is adaptively chosen corresponding to design objectives. The digital filter was simulated to prove the validity of the model and it was compared with the Hamming, the Manning, the Blacknan and the Kaiser window function. And we have used peak side-lobe and transient characteristics as standard of judgement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.895-902
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• 2012

In this paper, we propose a novel equalizer to compensate for the group delay including AM/PM nonlinear distortion characteristics by the nonlinear power amplifier (PA). The group delay characteristic is a nonlinear non-constant time delay that appears differently depending on each frequency component. The phase distortion by AM/PM characteristics arising from the power amplifier is a major factor to increase group delay. By the group delay distortion, the signal in the constellation expands and is rotated. Considering the problem mentioned above, the nonlinear time delay that appears differently depending on each frequency component is classified as a static group delay and AM/PM characteristic of PA, the different phase transitions depending on the size of input signal as a dynamic group delay. Static group delay estimates and compensate for phase distortions in the frequency domain with type-based method and dynamic group delay compensates for phase rotation in the time domain. We confirmed that the group delay compensation techniques were enough to compensate the group delay characteristics including AM/PM characteristics of the power amplifier.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.63-72
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• 2007

This paper addresses the system development that can transfer data and TDM signals simultaneously by adding TDM pseudowires functions to E-PON system. E-PON technology is one of many technologies which can realize FTTH, has raised as next generation access network solution having both low-cost Ethernet technology and optical infrastructure. TDM pseudowires service is the new voice/data conversion technology which can transfer the existing TDM circuit switched voice and data over packet switching network. In this paper, this system can provide both data and TDM service without deteriorating QoS by adding TDM pseudowires service module to E-PON, and then implementing QoS control function. Therefore, the competitive system which can transfer both data and TDM signal, can be installed.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.306-311
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• 2000

This paper deals with the development of Laser Doppler Vibrometer (LDV) that can mea~ure the tlequency and amphlude of the ultrasonic vibralion. Hc-Ne laser (632.8 om) is used as a light source, and Michelson interferometer in winch frequency of the objective beam is shIfted by Bragg cell IS adopted The frequency modulated signal centered at 40 MHz flom the PIN diode IS amplified. down-col1vel1ed to 2.5 MHz, filtered and digiLized. The voltage output that is proportional to the velocity of the vibratwg surface is obtawed using digItal PLL. A microprocessor is used to extract the frequcncy aud amplitude of the vibratIOn from the voltage output. It is found that the developed LDV can measure up to 300 kHz vibratIOn and the mlillmUITI measurable amplitude is I nm at 300 kHz. We believe thatlhis LDV can be used to measure the vibratIOn of the heavy electric maclllnery and micro-size structures. tures.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.6
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• pp.438-444
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• 2019

In this paper, we proposed a 16-element array antenna design to improve signal detection performances. The array antenna characteristics, such as mutual coupling, pattern deviation, and half power beamwidth of the active element, were examined to obtain an optimal spacing between individual elements. The single element of the array antenna consists of an indirect feed using L-shaped feed and shorted radiating patch to achieve a broadband operation. Root mean square(RMS) errors based on the incident angle of the signal were calculated to verify the signal detection performance of the proposed antenna. The results demonstrate that the proposed array antenna with optimal spacing is suitable for detecting interference signals with low RMS error.

• Journal of Korean Society of Disaster and Security
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• v.14 no.2
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• pp.43-50
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• 2021

In Korea, the frequency of soil disasters has soared recently due to increased torrential rains caused by abnormal weather conditions. In particular, soil generated from mountainous areas is flowing into small rivers along valleys, depositing rivers and adding to flood damage. In order to prevent damage from such soil disasters, it is important to predict sediments and to quantitatively identify bed load. In this work, we conducted an experiment to indirectly measure acoustic sensor-based bed load collision sounds using pipe hydrophones, and compared them with raw data by applying denoising methods to improve the reliability of the measured data. As a result, we derive results in a more clear analysis of bed load estimation by correcting noise when the denoising method is applied to raw data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.711-717
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• 2017

The railway is a public transportation system that provides large-scale passenger transportation and service, whose reliability and safety is the top priority. The wiring of railway vehicles is classified into train control lines (train lines) and communication lines. The train lines are used for input / output signals related to vehicle driving and safety functions, and the communication lines are used for the input / output signals for passenger services such as broadcasting. In order to measure the reliability of railway vehicles, a train line is applied to the input / output interface of the control signals between the electric control devices in the vehicle, and there are many electromechanical devices such as relays and contactors for the control logic. In fact, since the vehicle control circuit is composed of several thousand contacts, it is difficult to check for errors such as contact failure, and it is impossible to check the real-time status, so a lot of manpower and time is required for regular maintenance. Therefore, we analyze the current state of the train line design of the electric equipment used for driving and services in domestic railway cars and propose three wiring reduction methods to improve it. Based on the analysis of domestic electric vehicles, it was confirmed that the wiring reduction effect is 35% or more.

• The Korean Journal of Nuclear Medicine
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• v.34 no.1
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• pp.82-93
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• 2000

Purpose: We characterized the signals obtained from the components of a small gamma camera using Nal(Tl)-position sensitive photomultiplier tube (PSPMT) and optimized the parameters employed in the modules of the system. Materials and Methods: The small gamma camera system consists of a Nal(Tl) crystal ($60{\times}60{\times}6mm^3$) coupled with a Hamamatsu R3941 PSPMT, a resister chain circuit, preamplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a resistive charge division circuit which multiplexes the 34 cross wire anode channels into 4 signals (X+, X-, Y+, Y -). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated and digitized via triggering signal and used to localize the position of an event by applying the Anger logic. The gamma camera control and image display was performed by a program implemented using a graphic software. Results: The characteristics of signal and the parameters employed in each module of the system were presented. The intrinsic sensitivity of the system was approximately $8{\times}10^3$ counts/sec/${\mu}Ci$. The intrinsic energy resolution of the system was 18% FWHM at 140 keV. The spatial resolution obtained using a line-slit mask and $^{99m}Tc$ point source were, respectively, 2.2 and 2.3 mm FWHM in X and Y directions. Breast phantom containing $2{\sim}7mm$ diameter spheres was successfully imaged with a parallel hole collimator. The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We proposed a simple method for development of a small gamma camera and presented the characteristics of the signals from the system and the optimized parameters used in the modules of the small gamma camera.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.403-406
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• 2000

파라메트릭 송파 방식을 공기중에서의 음향 변환기에 적용시키기 위한 검토로써, 비교적 공진 주파수가 낮은 기중 초음파 발생 소자를 이용하여 파라메트릭 송파기를 제작하였다. 실험에서는 송파기로서 공진주파수 38.6kHz를 갖는 음원을 제작하여 이용하였다. 비선형 왜곡으로부터 파라메트릭 어레이에 의한 차주 파수가 발생함을 알아보기 위하여 1kHz의 차주파수를 갖도록 38.1kHz와 39.1kHz의 1차파를 신호발생기로부터 인가하고 마이크로폰을 사용하여 수신하였다. 공기중에서 파라메트릭 효과의 확인을 통하여 파라메트릭 송파기에서 방사되는 1차파와 전파경로중에서 생성하는 2차파의 거동을 이론면에서 고찰하고, 실험 결과와의 비교 검토를 행하여 기중 파라메트릭 송파기 개발의 가능성을 검토하여 보았다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1656-1657
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• 2011

본 논문에서는 RF 프로브를 이용하여 평면 구조물의 RCS(Radar Cross Section)를 감쇄시키기 위한 방법을 제안하였다. 우선적으로, EM 시뮬레이터를 이용하여 제안한 방법에 대한 가능성을 증명한 후 실험을 수행하였다. x-band 에서 $10{\lambda}$의 알루미늄판 위에 FR4 기판을 이용하여 patch 형태로 제작된 RF 프로브를 설치하였으며, 그 후 알루미늄 판으로 입사되는 외부 전자파를 상쇄시키기 위하여 RF 프로브로부터 전자파를 방사하였다. 로테이터를 사용하여 알루미늄판을 phi 방향으로 회전하여 임의의 각도로 입사하는 평면파에 대해서도 반사파의 크기를 측정하였다. RF 프로브로부터 방사된 전자파의 세기와 위상은 신호 발생기와 위상 천이기를 이용하여 조절되었다. 결과적으로 무반향실에서의 실험을 통해, 알루미늄판에 의해 반사되는 전자파를 측정하여 외부 전자파의 상쇄 정도를 확인하였다.