• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.223-230
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• 2006

We demonstrate a distributed fiber sensor system based on spatially-selective Brillouin scattering, using a single laser diode as a light source whose optical frequency is directly modulated by the injection current. The pump and the counter-propagating probe lights, which are sinusoidally frequency-modulated, are superposed in the fiber so that stimulated Brillouin scattering takes places only at a specific location along the fiber. Brillouin gain peak position is controlled by varying the modulation frequency. Distributions of Brillouin shift frequency are measured for the case of concatenated optical fibers of two different kinds and also for the case of temperature distribution. The temperature coefficient of the Brillouin shift frequency is measured to be $1.33MHz/^{\circ}C$.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.4
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• pp.184-188
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• 2006

This paper presents DSP based narrow band satellite communication signal power detector for tracking control of mobile satellite antenna system. An analog filter based conventional power detector has poor performance due to frequency drift of carrier. Also, it is very difficult to change an analog filter bandwidth according to changed bandwidth of transmitted signal. To solve these difficulties, we proposed DSP based signal power detector, which is easy to change bandwidth of filter and to match shifted frequency of carrier. The proposed signal power detector consists of a FFT function to measure frequency drift of carrier, a programmable filter bank function to limit of received signal bandwidth and a power calculation function to measure power of filtered signal in 12-bit linear scale. Test results of implemented signal power detector, based on TMS320C5402 DSP, showed that it satisfied required functions and performances and properly operated.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.6
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• pp.124-131
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• 2003

In this paper, we propose a Progressive scalable video coding algorithm using frequency weighting in the DCT domain. Since the human visual system (HVS) can be modeled as a nonlinear point transformation, called the modulation transfer function (MTF), we tan use the frequency weighting matrix to enhance the video image quality. We change this frequency weighting matrix into the frequency shift matrix to apply to the bit-plane coding method for the fine granular scalable (FGS) video coding We also define a new error metric JNDE (just noticeable difference) to measure the perceptual image quality in terms of human vision.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.763-767
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• 2008

In a speech coding system using excitation source of voiced and unvoiced, it would be involved a distortion of speech qualify in case coexist with a voiced and an unvoiced consonants in a frame. So, We proposed TS(Transition Segment) including unvoiced consonant searching and extraction method in order to uncoexistent with a voiced and unvoiced consonants in a frame. This research present a new method of TS approximate-synthesis by using Least Mean Square and frequency band division. As a result, this method obtain a high quality approximation-synthesis waveforms within TS by using frequency information of 0.547kHz below and 2.813kHz above. The important thing is that the maximum error signal can be made with low distortion approximation-synthesis waveform within TS. This method has the capability of being applied to a new speech coding of Voiced/Silence/TS, speech analysis and speech synthesis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.2
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• pp.124-132
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• 1987

In this paper, a new Open and Closed Loop Alternation(OCLA) frequency synthesizer is developed to eliminate a frequency error occurring in the transition state of a frequency hopping. This frequency synthesizer consists of a phase comparator(PC), two low pass filters(LPF), two voltage controlled oscillators(VCO), switching elements, a programmable divider and frequency hopping controller, and the stabilized output frequency can be obtained by switching performance. In addigion, it can be found that the characteristic of its circuit construction makes it easy to attach an external circuitry to the open loop.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.233-236
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• 2005

국내외적으로 M/W 중계용 주파수 대역은 3${\sim}$30GHz 대역이다. 그러나 갈수록 늘어나는 서비스와 전송용량의 증대로 인해 주파수 부족현상이 일어나는 추세이다. 이에 대한 방안으로 주파수 재배치에 관한 문제가 대두되고 있다. 이동방송 중계용 링크인 FPU 링크는 차후 다른 주파수 대역으로 이전시 이전의 링크에서 사용되었던 시스템 제원을 토대로 필요한 대역에 대해 다양한 변조방식으로 시뮬레이션 평가 후 이용채널 개수 및 이전 가능 여부등과 같은 조치가 수행되어져야 한다. 본 논문에서는 M/W 대역 휴대용 디지털 무선전송 시스템으로써 디지털 FPU 링크 시스템을 모델링하고 이동환경에서 발생하는 도플러 천이 효과를 고려한 Clark & Gans 페이딩 채널 모델을 고려하여 페이딩의 영향에 따른 시스템 성능을 분석하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.6
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• pp.553-558
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• 2011

This paper describes the development and test result of S-band Transmitter flight model(FM) of STSAT-3 by satellite research center(SaTReC), KAIST. The communication sub-system of STSAT-3 is consist of two different frequency band channels, S-band for Telemetry & Command and X-band for mission data. S-band Transmitter(STX) functionally made of modulator, frequency synthesizer, power amp and DC/DC converter. The transmission data is modulated by FSK(Frequency Shift Keying) and the interface between spacecraft sub-module and STX is RS-422 standard method. The FM STX is based on modular design. The RF output power of STX is 1.5W(31.7dBm) and BER of STX is under $1{\times}10^{-5}$ which meets the specification respectively. The FM STX is delivered Spacecraft Assembly, Integration and Test(AIT) level through the completion of functional Test and environmental(vibration, thermal vacuum) Test successfully.

• Journal of Internet Computing and Services
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• v.7 no.4
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• pp.57-66
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• 2006

In this paper, I propose a new method of Multi-Pulse Speech Coding(FBD-MPC: Frequency Band Division MPC) by using TSIUVC(Transition Segment Including UnVoiced Consonant) searching, extraction and approximation-synthesis method in a frequency domain. As, a result. the extraction rates of TSIUVC are 84.8%(plosive), 94.9%(fricative) and 92.3%(affricative) in female voice, 88%(plosive), 94.9%(fricative) and 92.3%(affricative) in male voice respectively. Also, I obtain a high quality approximation-synthesis waveforms within TSIUVC by using frequency information of 0.547kHz below and 2.813kHz above. I evaluate MPC by using switching information of voiced/unvoiced and FBD-MPC by using switching information of voiced/Silence/TSIUVC. As, a result, I knew that synthesis speech of FBD-MPC was better in speech quality than synthesis speech of the MPC.

• Journal of Satellite, Information and Communications
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• v.3 no.1
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• pp.8-14
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• 2008

In this paper, we analyze throughput performance of MF-TDMA scheme and QS MC-DS/CDMA(quasi-synchronous MC-DS/CDMA) scheme based on scrambling on WH sequence and PPGC sequence in early frequency offset caused by high speed transfer terminal. QS MC-DS/CDMA scheme with scrambled WH sequence shows 5.7% higher throughput than MF-TDMA scheme and 8% higher throughput than QS MC-DS/CDMA with PPGC sequence in high speed transfer terminal environment such as maximum 1000Km/h speed with high frequency of Ka-band. Finally, we show that QS MC-DS/CDMA scheme with scrambled WH sequence is more efficient than traditional MF-TDMA scheme at the aspect of throughput in DVB-RCS system with Ka frequency band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.6
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• pp.686-698
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• 1989

In this paper, The new algorithm of spectrum moment for format frequency estimation is proposed. The second oder and the third order spectrum moment, which reflect variance and skewness of a spectrum pattern, respectively, is utilized to adjust the frequency region for estimation precision of format frequency. As the results. the F1-F2 diagram reported 8 Korean vowels for man and woman and that we found articulation method of vowel and vowel, vowel and consonant.