• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.754-756
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• 2013

The modern Electronic Warfare Receivers are required to the current radar technologies like the Low Probability of Intercept(LPI) radars to avoid detection. LPI radars have features of intra-pulse modulation differ from existing radar signals. This features require counterworks such as signal confirmation and identification. Hence this paper presents a study on intra-pulse modulation recognition. The proposed method automatically recognizes intra-pulse modulation types such as LFM and NLFM using classifiers extracted from the features of each intra-pulse modulation. Several simulations are also conducted and the simulation results indicate the performance of the given method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.2009-2019
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• 2013

In this paper, we propose an automatic modulation recognition algorithm based on cyclic moment and new modified cumulant for analog and digital modulation signals. It is noteworthy that each modulated signal has different cycle frequency characteristics according to its order of cyclic moment. By means of this characteristics as classification features, various modulated signals can be efficiently classified. Also, to identify modulated signals having the same cycle frequency characteristics, we take advantage of the additional classification factors such as variations of envelope and phase as well as modified cumulant. The proposed algorithm was evaluated by considering the number of symbols, SNR, and frequency offset. In the simulation condition where the number of gathered symbols was about 819, and SNR and frequency offset were above 10dB and below 25%, respectively, the average accuracy of the proposed algorithm was more than 95%.

• Broadcasting and Media Magazine
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• v.11 no.1
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• pp.86-92
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• 2006

점차 사용 가능한 대역이 포화됨에 따라 이미 할당된 스펙트럼 자원을 효율적으로 공유하고자 하는 무선인지(cognitive radio) 기술이 대역포화 문제를 해결할 수 있는 주요한 기술로 등장하고있다. 이 원고에서는 광대역 무선인지 기술에 필요한 물리계층에서의 필요조건을 살펴보고 이에 적합한 변조방식에 대해 살펴본다. 특히 광대역 무선인지 기술에 필요한 유연성을 제공할 수 있고 인접채널 간섭을 크게 감소시킬 수 있는 웨이블릿 패킷 변조(wavelet packet modulation: WPM) 기술에 대해 소개한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2409-2416
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• 2014

In this paper, an automatic recognition algorithm for linearly modulated signals like PSK, QAM under noncoherent asynchronous condition is proposed. Frequency, phase, and amplitude characteristics of digitally modulated signals are changed periodically. By using this characteristics, cyclic moments and higher order cumulants based features are utilized for the modulation recognition. Hierarchial decision tree method is used for high speed signal processing and totally 4 feature extraction parameters are used for modulation recognition. In the condition where the symbol number is 4,096, the recognition accuracy of the proposed algorithm is more than 95% at SNR 15dB. Also the proposed algorithm is effective to classify the signal which has carrier frequency and phase offset.

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.3-12
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• 2001

It is known that the roughness is one of the most important metrics in assessing the sound quality. In this study, a new roughness model is suggested by combing the previous auditory filter model and several signal processing methods for the enhancement of calculation efficiency and accuracy. For testing the usefulness of the present model, the predicted responses are compared with the experimental data and it is observed that they are in good agreements. Also, it is found that the previous models have limitations to search frequency components mainly contributed to overall roughness. By modifying the correlation criteria of the present model, the revised model for the proper estimation of roughness-contributed components is embedded.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.250-253
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• 1997

The effect of dispersion in optical transmission system changes according to chirp and SPM. Chirp depends on the modulation condition of an external modulator. SPM is proportional to signal power. In this paper, we analyzed the pulse broadening due to SPM and chirp in the system with dispersion by using Split Step Fourier Method and calculated the optimum chirp parameter for 400 km transmission system. Experimental results are presented also.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.66-74
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• 2002

The characteristics of the satellite image quality parameters driven by satellite imaging instrument are investigated. Since the satellite image is directly produced by the satellite imaging instrument, the satellite image quality depends on the imager performance highly. This is why the imager performance parameters are considered as an important part of the satellite image quality parameters. The imager performance parameters consist of spectral band parameters, ground sample distance(GSD) parameters, swath width parameters, imager Modulation Transfer Function (MTF), imager Signal to Noise Ratio(SNR), radiometric response characteristics parameters, pixel registration, and imager calibration.

• Journal of the Korea Society of Computer and Information
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• v.27 no.8
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• pp.211-218
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• 2022

In this paper, a computer simulation program was developed to interpret the results measured by photoreflectance spectroscopy. The developed program is implemented so that the user can easily change the factors required for optical modulation characteristic interpretation, and the result of the value can be checked simultaneously with the actual measurement result. The results obtained by photoreflectance spectroscopy are obtained by mixing a third derivative function form (TDFF) modulated around a bandgap with a Franz-Keldysh oscillation (FKO) signal due to an electric field at a surface and an interface higher than the bandgap. Through the computer simulation program, the optical characteristics that appear in the GaSb Epi layer formed as a single layer were analyzed, and very useful results were obtained by specializing in optical modulation analysis. In addition, a Fast Fourier Transform (FFT) analysis tool was added to facilitate frequency characteristics analysis of FKO.

• Clinical and Experimental Pediatrics
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• v.49 no.5
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• pp.507-512
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• 2006

Purpose : Early detection and intervention of hearing impairment is believed to improve speech and language development and behavior of children. The aim of this preliminary study was to determine the prevalence of hearing impairments, and to identify the association of risk factors relating to refer response in high risk neonates who were screened using distortion product otoacoustic emissions (DPOAE). Methods : The subjects included 871 neonates who were admitted to the neonatal intensive care unit of the Pediatric Department in Soonchunhyang University Bucheon Hospital from May, 2001 to December, 2004. They were screened using DPOAE. Based on DPOAE, we divided the neonates in two groups : 'Pass' and 'Refer'. The differences in risk factors between the pass group and the refer group were analyzed. Results : The incidence of the refer group was 12.1 percent(106 out of 871). The bilateral refer rate was 5.4 percent(47 out of 871). And the unilateral refer rate was 6.7 percent(59 out of 871). Gender, birth place, family history of hearing loss, small/large for gestational age, obstetrical factor, hyperbilirubinemia and use of gentamicin were not statistically related to the refer rate. Statistically related to refer rate were birth weight, resuscitated neonates, Apgar score, craniofacial anomaly, mechanical ventilator application, sepsis, using of vancomycin(P<0.05). The prevalence of hearing impairment (${\geq}60dB$) in this study was 2 percent(18 out of 871). Conclusion : This study showed a higher prevalence of hearing impairment in high-risk neonates. Thus neonatal hearing screening should be carried out in high-risk neonates.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.34-34
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• 2003

목적 : 폐암 환자 세기변조방사선치료 과정을 소개하고, 방사선치료계획의 최적화를 위한 빔 수와 방향, 가상장기 설정 (virtual organ delineation, VOD) 및 선량 제한 인자들의 이용에 대해 평가함으로써 폐, 심장 등에 조사되는 선량을 최소화하는데 사용하는 세기변조방사선치료 (intensity modulated radiotherapy, IMRT) 기술의 유용성을 평가하고자한다. 대상 및 방법 : 종양이 종격동을 침범하여 상대적으로 장기움직임에 의한 오차가 적은 폐암환자 5 명을 대상으로 하였다. 환자고정장치는 상반신을 편안하게 유지함과 동시에 팔의 위치를 고정시킴으로써 기대할 수 있는 환자고정효과와 벨트를 이용하여 환자 상복부를 압박해줌으로써 호흡운동에 의한 장기 움직임을 감소시킬 수 있는 형태로 고안하였다. 치료계획시 빔 수와 방향은 5,7,9 문 (from 200 to 160, equispaced field, arbitrary field), 4 문 (anterior, posterior, bilateral posterior oblique field) 과 비등방 7, 9 문 (non-equispaced field, arbitrary field) 등을 사용하였다. 선량제한 ($V_{20}V_{25}$)은 문헌에 기초하여 설정하였으며, 가상장기를 적절히 사용하여 최적화된 치료계획 결과를 얻었다. 방사선치료계획 평가는 선량-체적간 히스토그람 (DVH), 등선량곡선 및 선량통계 등을 이용하여 수행하였다. 특히 가상장기 설정 전, 후의 결과 값을 분석함으로써 그 유용성을 확인하였다. 결과 : 9문 등방-IMRT와 7문 비등방-IMRT 방법이 치료계획용적의 선량균질성 (PTV dose homogeneity), 평균 폐선량 (mean lung dose) 및 $V_{20}V_{25}$ 모두에서 20% 이내의 좋은 결과를 얻을 수 있었고, 가상 장기를 설정함으로써 같은 결과를 가져옴을 알 수 있었다. 또한 폐암 세기변조방사선치료 프로토콜을 작성하여 임상에 사용함으로써 치료과정 중 발생할 수 있는 오류를 보완할 수 있음을 알 수 있었다. 결론 : 폐암 세기변조방사선치료 시 사용할 수 있는 프로토콜을 작성하였고, 적절한 가상 장기 및 조사계획 설정으로 치료계획의 최적화를 얻을 수 있음을 알 수 있었다.