• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.163-171
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• 2003

To evaluate the performance of the digital radiography(DR) system developed in our group, the modulation transfer function(MTF) was measured and compared with that of an analog X- ray detector, film/screen system. The DR system has an amorphous selenium(a-Se) layer vacuum-evaporated on a TFT flat panel detector. The speed class 400 film/screen (Fuji) system has been being used in the clinical field as analog X-ray detectors. Both the square wave and slit method were used to evaluate their MTF. The square method was applied to both film/screen and the DR system. The slit method, however, was applied to only DR system. The full-width half maximum resolution of film/screen was 357${\mu}{\textrm}{m}$(1.4 lp/mm at 50% spatial frequency), and the resolution of DR was limited to 200${\mu}{\textrm}{m}$(2.5 lp/mm at 30%). These results indicate the measured resolution limitations approximate to the pixel pitch, 139 ${\mu}{\textrm}{m}$ of TFT. The MTF of DR is higher than that of film/screen by the factor of 1.785. It is proved that our a-Se based DR system has potential usefulness in the clinical field.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2B
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• pp.59-68
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• 2008

In order to activate the digital broadcasting in Korea, the analog broadcasting will have been closed down until 2012. Recently IPTV(Internet Protocol TV) thorough internet has been regarded as the fourth media following the terrestrial, satellite, and cable for the digital broad casting. And it has been the important medium for the communication and broadcasting system. However IP is not easy to replace the entire broadcasting system with the digital - type broadcasting system. For the digital broadcasting, we should replace all TV sets, install the settop-boxes to receive the various IP media, solve problems about time delaying when changing channels, and support communication and broadcasting consolidation service for such as PVR and Network CCTV. IPMG is the digital converter that is able to solve these problems. In this paper, I'll develop and analyze IPMG converter's performance which sends and receives both the analogue and digital broadcasting signals through various media gives the Network PVR service.

• The KIPS Transactions:PartB
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• v.12B no.4 s.100
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• pp.443-450
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• 2005

Digital fingerprinting is a contents-protection technique, where customer information is inserted into digital contents. Fingerprinted contents undergo various attacks. Especially, attackers can remove easily the inserted fingerprint by collusion attacks, because digital fingerprinting inserts slightly different codes according to the customers. Among collusion attacks, averaging attack is a simple, fast, and efficient attack. In this paper, we propose a video fingerprinting system that is robust to the averaging attack. In order to achieve code efficiency and robustness against the averaging attack, we adopt anti-collusion code (fingerprint code) from GD-PBIBD theory. When the number of users is increased, the size of fingerprint code also grows. Thus, this paper addresses a zero-based code modulation technique to embed and detect this fingerprint code efficiently. We implemented a blind video fingerprinting system based on our proposed technique and performed experiments on various colluding cases. Based on the results, we could detect most of colluders. In the worst case, our scheme could trace at least one colluder successfully.

• Journal of Digital Convergence
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• v.10 no.4
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• pp.243-250
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• 2012

This study proposes new protocol protecting patients' personal record more safely as well as solving medical dispute smoothly by storing the record not into a computer server in hospitals but into the National Health Insurance Corporation computer server. The new protocol for electronic medical record is designed using RSA public key algorithm and DSA digital signature. In addition, electronic medical record systems are built up with more safety and reliability through certificate authority. The proposed medical information systems can strengthen trust between doctors and patients. If medical malpractice occurs, the systems can also provide evidence. Furthermore, the systems can be helpful to reduce medical accidents. The systems could be also utilized efficiently in various applied areas.

• Current Industrial and Technological Trends in Aerospace
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• v.8 no.1
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• pp.86-95
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• 2010

Flight termination system(FTS) is used to terminate safely the launch vehicle's flight when it faces an emergency situation by transmitting termination command from ground FTS. RCC standard IRIG tone method has been used widely for FTS commands method in foreign ranges and Naro Space Center, but this method has a weakness for security of command signal. Therefore RCC had studied more secured EFTS standard and chose CPFSK digital modulation method. This paper describes basic concept and types of FTS and FTS types which foreign ranges had applied and describes standardization of EFTS in the U.S. based on RCC EFTS study reports.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.218-222
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• 2001

본 논문에서는 B-WLL 상향링크 수신기용 심볼 및 위상 동기 회로를 설계하였다. B-WLL 상향링크는 버스트 전송 방식이고, 변조 방식은 QPSK를 사용한다. 본 연구에서는 심볼율을 2.5 Msymbol/sec로 가정하였고, 디지털 Up/Down Converter를 이용한 IF 대역은 20 [MH]를 사용하였다. 수신필터는 25 탭, 7 비트 계수를 가지는 FIR 필터로 설계하였다. 심볼 타이밍 복구 회로는 Gardner 알고리즘을 이용하여 설계하였으며, 반송파 복구는 결정 지향 알고리즘을 이용하여 설계하였다. 설계된 알고리즘은 VHDL로 코딩되어 FPGA에 구현되었다. 실험에 사용된 FPGA는 ALTERA사의 APEX20KE 시리즈의 60만 게이트 FPGA이다. 구현된 복조기의 성능을 평가하기 위하여 모의실험 결과와 구현 결과를 비교하여 제시하였다. 그 결과로 주파수 오프셋과 위상 오프셋이 있는 경우에도 심볼 타이밍 복구 회로는 잘 동작을 하였으며, 주파수 오프셋이 심볼율의 0.12%까지 위상 동기회로가 잘 동작하였다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.4
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• pp.467-473
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• 1999

We have realized the two kinds of power line communication systems by the FSK MODEM. The first approach is the DS-SS (Direct suquence-spread spectrum) technique using 8 bits pseudo noise, the other is Convolutional coding method by the new algorithm. Their characteristics are comparied with each other by experimenting their Bit Error Rates (BER) in high level of Noise. The results have showed that two systems are useful to the application of HA (Home Automation) systems.

• Progress in Medical Physics
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• v.21 no.3
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• pp.239-245
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• 2010

The purpose of this study is to comprehensively compare and evaluate the characteristics of image quality for digital mammography systems which use a direct and indirect conversion detector. Three key metrics of image quality were evaluated for the direct and indirect conversion detector, the modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE), which describe the resolution, noise, and signal to noise performance, respectively. DQE was calculated by using a edge phantom for MTF determination according to IEC 62220-1-2 regulation. The contrast to noise ratio (CNR) was evaluated according to guidelines offered by the Korean Institute for Accreditation of Medical Image (KIAMI). As a result, the higher MTF and DQE was measured with direct conversion detector compared to indirect conversion detector all over spatial frequency. When the average glandular dose (AGD) was the same, direct conversion detector showed higher CNR value. The direct conversion detector which has higher DQE value all over spatial frequency would provide the potential benefits for both improved image quality and lower patient dose in digital mammography system.

• Smart Media Journal
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• v.7 no.3
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• pp.29-34
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• 2018

This paper presents a study on adapting optical communication technology using infrared ray for the enhancement of hearing aids in noisy environment. The transmitter module containing microphone and infrared ray-emitting diode converts audio signal to infrared optical signal and sends it out in the air. The receiver module located in a distance receives the infrared signal, converts it to electrical signal, and transfers it to an input of a digital hearing aid. Especially, the receiver module needs to be small, low voltage, and consume low power since it will be attached to hearing aids. Experiments with applying infrared communication technology of digital modulation method and analog non-modulation method show that the analog non-modulation method is adequate for infrared communication of approximately 5m distance indoor. Prototypes of transmitter module and receiver module were manufactured, and internal parameters of the digital hearing aid were adjusted to confirm normal transmit-receive operation of audio signals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7B
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• pp.1081-1090
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• 2010

$0.18{\mu}m$ CMOS UHF RFID tag frontend is presented in this paper. Several key components are highlighted: the voltage multiplier based on the threshold voltage terminated circuit, the demodulator using current mode, and the clock generator. For standard compliance, all designed components are under the EPC Global Class-1 Generation-2 UHF RFID protocol. Backscatter modulation uses the pulse width modulation scheme. Overall performance of the proposed tag chip was verified with the evaluation board. Prototype Tag Chip dimension is neary 0.77mm2 ; According to the simulation results, the reader can successfully interrogate the tag within 1.5m. where the tag consumes the power about $71{\mu}W$.