• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.1181-1184
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• 2003

본 논문은 광대역 적응형 위성방송 전송기술에서 전송채널의 환경변화에 적응적으로 대처하기 위한 방법에 국한하며 방송 서비스에 적합한 채널 적응형 전송구조로 계층적 변조방식과 시분할 AMC 전송구조를 제안하고 전송특성 및 구조를 분석하여 장단점을 비교한다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.324-325
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• 2003

광섬유 브래그 격자 센서(Fiber Brags Grating Sensor： FBG Sensor)는 여타 광섬유 센서와 같이 가볍고 저렴하며 주위의 전자기적 잡음에 무관한 장점과 더불어 측정대상이 반사광의 파장변화이므로, 광섬유 연결부나 실험장치들에 의해 생기는 광 손실이나 잡음에 대해서 강인한 측정을 할 수 있다. 그리고 파장변화가 변형률이나 온도변화에 선형적으로 나타나므로, 센서로서 많은 연구가 진행되고 있다. 특히, 구조물의 내부에 삽입하여 구조물 스스로 외부의 환경변화를 감지하여 필요한 동작을 수행하는 지능형 구조물(Smart Structure)에 적합한데, 이를 위해선 구조물의 여러 지점을 측정해야 하므로, 브래그 격자 여러개를 한 시스템에서 사용하는 다중화(Multiplexing)가 필수적이다. (중략)

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.4
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• pp.635-643
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• 2014

Most of the web-based services are provided by a web browser. A web browser receives a text-based web page from the server and translates the received data for the user to view. There are a myriad of add-ons to web browsers that extend browser features. The browser's add-ons may access web pages and make changes to the data. This makes web-services via web browsers are vulnerable to security threats. A web browser stores web page data in memory in the DOM structure. One method that prevents modifications to web page data applies hash values to certain parts in the DOM structure. However, a certain characteristic of web-pages renders this method ineffective at times. Specifically, the user-input data is not pre-determined, and the hash value cannot be calculated prior to user input. Thus the modification to the data cannot be prevented. This paper proposes a method that both detects and inhibits any attempt to change to user-input data. The proposed method stores user-input from the keyboard and makes a comparison with the data transmitted from the web browser to detect any anomalies.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.40-47
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• 2001

The structural dependence of the performance of an 1.55 $1.55{\mu}m$ InGaAsPIInGaAsP MQW electro-absorption modulator for highspeed digital fiber communication was systematically investigated. The effects of n-doped SCH region length $t_n$ as well as the general structure parameters including quantum well number $N_w$, well-thickness $t_w$, detuning wavelength $\Delta\lambda$, and device length L were thoroughly analyzed. Thereby, a high-pelfoIDlance electro-absorption modulator with device length L of $100{\mu}m$ was successfully designed. The designed structure showed excellent characteristics that have residual loss less than -1.5 dB, operational voltage from 0 V to -2V, and extinction ratios of -2.92 dB at $V_{\alpha}$=-1 V and -10 dB at $V_{\alpha}$=-2V.X>=-2V.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1774-1781
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• 1997

In this paper, we propose a full digital frequency and phase locked loop for CATV and HDTV receivers adopting VSB modulation. The CATV and HDTV receivers proposed by the Grand-Alliance in USA are ultilizing analog signal processing technology for carrier recovery. By the way, it is not a good architecture for the development of single chip ASIC operating in digital domain. To solve this problem while improving the performance, we first down convert the received r.f. signal to a near baseband signal for a low-rate AD converter and then we use digital signal processing techniques. The proposed system has the frequency pull-in range of -200 KHz +2.50 KHz. Moreover, it has the ability of adaptive loop bandwidth control according to the amount of frequency offset to improve the acquisition time while reducing the phase noise.

• The Journal of the Acoustical Society of Korea
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• v.23 no.4
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• pp.303-308
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• 2004

In this Paper a transmitter system for IMr-2000 using feed-forward linearization method was Proposed to linearize power amplifier. The feed-forward structure needs a reference signal to compare and neutralize distortion : this is achieved through the second modulator which is operated at very low input level to obtain a signal with a negligible distortion. Therefore, this structure can reduce distortion of modulator as well as Power amplifier. This is the advantage over the existing system structure. The Proposed transmitter system is designed and simulated by Agilent ADS ver.2002. A two tone test for the system is done at 1.98GHz center frequency with frequency spacing of 2MHz. The reduction of Inter-Modulation Distortion(IMD) is around 49.95dB. This proposed system offers an excellent combination of linearity and simplicity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.2
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• pp.65-70
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• 2004

This paper presents a novel linearization scheme for a nonlinear RF amplifier It is based on the amplitude modulation with envelope signal. The 3rd order distortion generator is composed of two FETs and it adopts a balanced structure for the purpose of main carrier cancellation. The amplitude and phase of the IM3 component can be controlled at RF band. This predistorter is implemented and tested at the KOREA PCS Tx. band (1840∼1870MHz). Experimental results of two-tone test show that the IM3 cancellation is achieved about 30-40 ㏈ for the wide dynamic range. The adjacent channel power ratio is improved by over 10 ㏈ at the broad-band CDMA signal with a peak to average power ratio of l0㏈, and this improvement is maintained through a wide range of output power levels.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.705-708
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• 2010

Recently, HSRC (Half-Symbol-Rate-Carrier) OQPSK (Offset Quadrature Phase Shift Keying) signaling which reduces the bandwidth of transmitted signal for high-speed data communications has been introduced. Since the signal is based on QPSK modulation, it also has the characteristics of QPSK signal. This paper introduces architectures of the transceiver using differential coding to resolve the 4-phase ambiguity problem of the HSRC-QOPSK signaling for high-speed data communications. In addition, this paper proves the functionality of the transceiver with differential coding and shows the BER (bit-error-rate) performance of the transceiver by simulations.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.3
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• pp.34-40
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• 2002

In this paper, a new encryption method for a binary image using Phase modulation and Fourier transform is proposed. For decryption we use the characteristics of square law detector. In encryption process, a key image is obtained by phase modulation of 256 level random pattern and its Fourier transformation, and input image is encrypted by Fourier transforming the multiplication of the phase modulated random pattern and phase modulated input image. The encrypted image and key image have only phase information, so they can not be copied or counterfeited and the original image can not be decrypted without the key image. To reconstruct the original image, each phase mask of the key image and the encrypted image must be placed on each path of the Mach-Zehnder interferometry with Fourier transform lens and the output image is obtained in the form of intensity in the CCD(Charge Coupled Device) camera. The real-time decryption is possible in the proposed system by use of a LCD as a phase modulator and a CCD camera as an intensity detector. The proposed method shows a good performance in the computer simulation and optical experiment as an encryption scheme.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.392-396
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• 2005

A new structure of tunable wavelength converter based on XCM in SOA was tried and analyzed. This converter used single SOA and had very simple structure. In this paper, results were experimentally obtained and demonstrated. Pump signal was generated with NRZ $(PRBS\;2^{31}-1)$ and data rate 2.5 Gbps. WDM multi conveted signals showed more than 8.3 dB extinction ratio. For BER performance, all these converted signals had within 5.0 dB power penalty compared with the pump signal. With these results, we showed that this converter was suitable for 2.5 Gbps WDM multi-channel wavelength converting.