• Journal of the Institute of Convergence Signal Processing
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• v.12 no.1
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• pp.33-37
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• 2011

This paper presents the frequency spectral analysis based on FFT of the infrared ray fire thermal image, it is an object to deduce the conditions for determining fire alarm through the image processing with the frequency domain. After the candidate regions are separated by using pre-defined brightness value, the fast fourier transform is performed for consecutive infrared thermal images, the frequency spectral analysis of the thermal image analyzed DC and AC frequency distribution. The fire criterion of the thermal image was presented based on the analyzed result and a practicality was confirmed through the computer simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.928-931
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• 2003

본 논문에서는 고속 광대역의 정보신호를 효율적으로 전송하기 위한 무선 LAN 채널환경에서 OFDM 전송방식을 사용할 때 반송파의 주파수 오프셋이 발생하는 동기 오차가 수신시스템에 미치는 영향으로 인한 수신 성능을 분석하였다. 성능개선 기법으로 Convolution Coding 기법을 적용함으로써 반송파 주파수 오프셋에 따른 성능 열화를 보상하였다. 성능 해석 결과, OFDM 시스템에서 주파수 오프셋이 커짐에 따라 성능이 열화됨을 알 수 있었고, (BER=$10^{-3}$)를 목표로 하는 경우 OFDM 시스템에 Convolution Coding 기법을 적용함으로써 성능 개선이 나타났지만 64QAM방식인 경우 주파수 오프셋 0.05, 0.1에서 주파수 오프셋에 의한 캐리어간 간섭의 영향이 지배적임을 알 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.516-522
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• 2010

In this paper, the carrier frequency offset estimator is proposed for the China multimedia mobile broadcasting (CMMB). The fractional carrier frequency offset is estimated by utilizing the cyclic prefix in each CMMB symbol. In addition, the integer carrier frequency offset can be estimated with the synchronization signal in every CMMB frame. The proposed estimator is the most suitable for the frame structure of CMMB. It shows a prominent performance even in timing offset and multipath conditions.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.97-103
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• 2005

본 고에서는 전력선통신 기술동향을 분석하고 국내 기술기준에서 어떻게 규제를 받는지 분석하였다. 전력선통신은 초기에 전기 이용기기의 원격 제어용으로 비교적 적은 데이터를 송수신하는데 이용되었다. 그러나 광대역 통신 요구에 따라서 전력선을 이용한 고속 전력선모뎀 기술이 개발되어 인터넷 등과 같은 고속 데이터 통신을 할 수 있게 되었다. 그러나 전력선통신은 기존 전선로를 사용하므로 높은 주파수의 신호를 전송하면 전파 방사에 의해서 다른 무선설비에 영향을 줄 수 있다. 현재 30MHz 이하의 대역을 사용하고 있으나 이 대역은 해상, 항공 등 인명 안전을 위한 중요 통신에서 이용하고 있다. 그러므로 전력선모뎀이 기존 무선설비에 간섭을 주지 않으면서 주파수 대역을 공유하기 위해서는 간섭을 최소화할 수 있는 spread spectrum이나 OFDM과 같은 기술을 활용해서 설계되어야 한다. 이미 이러한 기술들을 활용한 전력선 모뎀이 상용화되어 있으며 옥내 뿐 만 아니라 옥외까지 용도를 확장하기 위해서 간섭 완화기술 및 방법 등이 활발히 연구되고 있다. 본 고에서는 전력선통신의 고속화를 위한 기술 동향 및 간섭 완화 방법 기술을 분석하고, 구현된 시스템이 다른 무선설비와 간섭 없이 사용될 수 있도록 규정하고 있는 관련 기술기준을 분석하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.231-238
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• 2004

This paper presents the high speed noise reduction processing system using the modified discrete fourier transform(MDFT) on the frequency domain. The proposed filter uses the linear prediction coefficients of the adaptive line enhance(ALE) method based on the Sign algorithm The signals with a random noise tracking performance are examined through computer simulations. It is confirmed that the fast adaptive digital filter is realized by the high speed adaptive noise reduction(HANR) algorithm with rapid convergence on the frequency domain(FD).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.230-237
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• 2012

The ultrasonic resonance method was applied to detect the disbond interface and empty layer between steel and FRP of the exit cone. The ultrasonic resonance method can easily detect the disbond interface and empty layer by amplifying the ultrasonic signal, but pulse echo method is difficult to distinguish adhesive interface from disbond interface or empty layer. The resonance frequency was predicted using the pressure reflection coefficient of 3-layered medium, and measured from ultrasonic signal of the test block using Fast Fourier Transform. The ultrasonic resonance proved that the predicted resonance frequency was in good agreement with the measured resonance frequency.

• Journal of IKEEE
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• v.13 no.1
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• pp.1-10
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• 2009

Recently, some frequency domain CMA (Constant Modulus Algorithm) have been introduced in an effort to reduce computational complexities [1,2]. In [1], a fast algorithm that minimizing cost function designed for block input signal is employed, while in [2], a novel cost function that minimizing sample by sample input is used. Although, the two fast algorithm save computational complexities as compared to CMA, the convergence behaviors of the two fast algorithm show different results with repsect to CMA. Thus, in this paper, some analytical results on the error surface of the fast frequency domain CMA are introduced. From the analytical results, we show that the more recent algorithm [2] outperforms the previous algorithm [1]. Simulation results reveals that the recent algorithm [2] shows 50% enhanced convergence with respect to the old fast algorithm [1]. Also, we show that the recent fast algorithm [2] has comparable convergence performance with respect to conventional CMA algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1024-1031
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• 1999

In order to transmit high-speed wide band signals efficiently in multipath fading environments, M-ary QAM signalling combined with OFDM transmission technique is applied. In this paper, the effect of synchronization error caused by carrier frequency offset and SER(Symbol Error Rate) performance of OFDM-16QAM and OFDM-64QAM are theoretically analyzed. Our result shows that as the number of sub-carrier in OFDM system increases the frequency-offset caused inter-channel interference(ICI) increases significantly, and that an error floor occurs even at high SNR of OFDM system. For OFDM-64QAM, the error floor occurs at SER=1$\times$10-7 when a normalized frequency-offset is 0.001, in which the SNR degradation is much greater than that of OFDM-16QAM. From this study the maximum allowable frequency-offset of OFDM-16QAM and OFDM-64QAM systems can be determined to meet the specific SER requirement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1243-1250
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• 2014

In this paper, a wideband DDS module covering the frequency range from 0.5 to 1.1 GHz was designed and fabricated. The clock frequency of the DDS was selected 2.4 GHz in order for 600 MHz output bandwidth. Multiple spurious cancelling signals having same amplitude and $180^{\circ}$ phase difference compared to the spurious were created at the additional path and added to the output signal within DDS for the spurious performance improvement. The fabricated DDS module showed better spurious performance than the commercial DDS one more than 10 dB and frequency tuning time was 340 ns below.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.295-301
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• 2012

In this article, we have designed SHA, which has 12 Bit resolution at an input signal range of 1 $V_{pp}$ and operates at a sampling speed of 100 MS/s in order to use at front of high speed ADC. SFDR(Spurious Free Dynamic Range) of the proposed system drops to approximately 66.3 dB resolution when the input frequency is 5 MHz, and the sampling frequency is 100 MHz, however, the circuit without a feedthrough has 12 bit resolution with approximately 73 dB.