• 한국군사과학기술학회지
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• 제2권1호
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• pp.30-37
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• 1999

흙으로 침투하는 전파의 투과도와 흙에 의한 신호감쇄량을 계산하였다 대상 복합매질을 이층구조로 모델링한 후, 적분형태로 주어진 전계 표현식을 보였다. 불균일 복합매질에서는 체적산란이 일어나며, 이의 영향이 감안된 전파특성을 분석하기 위하여 반복법인 본(Born) 근사법을 사용하였다. 또한 불균일 복합매질이 가진 랜덤성의 정도는 분산과 상관길이에 의해 정해지도록 하였다. 흙에 함유된 수분량, 흙 입자의 반경, 온도 및 주파수를 변수로 하는 투과도 및 신호감쇄량 식을 제안하였다. 제안된 식으로부터 이들 변수에 따른 투과도 및 신호감쇄량의 변화를 보였다. 분석 결과, 수분이 함유된 경우에는 신호감쇄량의 변동폭이 온도에 따라서 크게 달라짐을 보게 되었고, 그 변동치는 일반적인 예상치를 훨씬 초과하였으며 그 물리적 이유를 설명하였다.

• 한국음향학회지
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• 제20권3호
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• pp.91-97
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• 2001

능동소나 시스템에서 표적신호의 근거리 정보가 중요해짐에 따라, 표적 음향산란 신호의 고유한 특성을 분석하기 위해 실험적인 방법과 시뮬레이션 기법이 사용된다. 본 논문에서는 표적신호 합성을 위해 축소표적 반향실험을 수행하였고. 자료의 분석 결과 축소표적의 음향산란은 거울면 반사의 영향이 큰 것으로 분석되어, 표적신호 합성에서 기하광학이론을 응용하였다. 복잡한 형태의 표적을 여러 표본형상으로 분리하고, 각 표본형상의 기여도를 신호의 위상과 강도를 줌으로써 계산하였으며, 표적신호 합성모델의 검증을 위해 실제 축소표적 실험 결과와 비교하였다.

• 한국안전학회지
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• 제19권1호
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• pp.23-30
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• 2004

Modern production systems are very complex by request of automation, and failure modes that occur in thisautomatic system are very various and complex. The efficient fault diagnosis for these complex systems is essential for productivity loss prevention and cost saving. Traditional fault diagnostic system which perforns sequential fault diagnosis can cause catastrophic failure during diagnosis when fault propagation is very fast. This paper describes the Real-time Intelligent Multiple Fault Diagnosis System (RIMFDS). RIMFDS assesses current machine condition by using sensor signals. This system deals with multiple fault diagnosis, comprising of two main parts. One is a personal computer for remote signal generation and transmission and the other is a host system for multiple fault diagnosis. The signal generator generates various faulty signals and image information and sends them to the host. The host has various modules and agents for efficient multiple fault diagnosis. A SUN workstation is used as a host for multiple fault modules and agents for efficient multiple fault diagnosis. A SUN workstation is used as a host for multiple fault diagnosis and graphic representation of the results. RIMFDS diagnoses multiple faults with fast fault propagation and complex physical phenomenon. The new system based on multiprocessing diagnoses by using Hierarchical Artificial Neural Network (HANN).

• 대한의용생체공학회:의공학회지
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• 제6권2호
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• pp.13-14
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• 1985

We have developed a microprogramir!able signal processor for real-time ultrasonic signal processing. Processing speed was increased by the parallelism in horizontal microprogram using 104bits microcode and the Pipelined architecture. Control unit of the signal processor was designed by microprogrammed architec- ture and writable control store (WCS) which was interfaced with host computer, APPLE- ll . This enables the processor to develop and simulate various digital signal processing algorithms. The performance of the processor was evaluated by the Fast Fourier Transform (FFT) program. The execution time to perform 16 bit 1024 points complex FF7, radix-2 DIT algorithm, was about 175 msec with IMHz master Clock. We can use this processor to Bevelop more efficient signal processing algorithms on the biological signal processing.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(5)
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• pp.117-120
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• 2000

Pulse oximetry is a well established non-invasive optical technique for monitoring the SpO$_2$ during anaesthesia, recovery and intensive care. Pulse oximeters determine the oxygen saturation level of blood by measuring the light absorption of arterial blood. The sensors consists of red and infrared light sources and photodetectors. In the measurement of the hemoglobin oxygen saturation, conventional method has required the technique of filtering of remove the noise, and of complex signal processing algorithm. So much time have required to signal processing. In this research, we separate AC signal and DC signal in the stage of signal detection. We filter the noise from each signal and convert A/D. We obtain the SpO$_2$ using the DSP algorithm.

• 한국전자파학회논문지
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• 제12권7호
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• pp.1086-1093
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• 2001

본 논문에서는 n차 오차신호발생기(error signal generator)를 이용한 postdistortion 방식의 RF 전력증폭기의 선형화 기법을 제안하였다. n차 ESG(error signal generator)는 전력증폭기의 기저대역 등가 복소 전달함수를 바탕으로 오차신호를 발생시켜, 이를 전력증폭기의 출력 단에서 n차 이하의 비선형성만을 제거한다. 따라서, 출력 단의 n차 이상의 혼변조 왜곡(intermodulation distortion) 성분에 영향을 미치지 않으며, 개루프(open-loop) 형태이므로 시스템의 안정성을 보장할 수 있다. 또한, 전력증폭기의 입력 신호를 이용하여 오차신호를 발생시키므로 feedforward 방식에서와 같이 오차신호 발생에 따른 주신호 경로(main signal path)의 시간지연 회로가 불필요하다. 실험 결과로 7차 ESG를 이용한 postdistorter를 최대 출력이 5 W인 셀룰러 대역 A급 증폭기에 적용한 경우의 혼변조 왜곡 개선도와 3-carrier CDMA 신호를 이용한 측정 결과를 제시하여 본 방법의 타당성을 검증하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.647-652
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• 2008

Railway signal system has been more complex, larger and required high reliability. So, maintenance by experience must be changed to optimize maintenance program or introduced systematic method for estabilish new maintenance program. In this paper, we introduced the maintenance period decision method which are Age based method and Block replacement method based on the failure distribution for the equipment. So, we allocated optimum maintenacne period for the railway signal equipment using block replacement method.

• 한국통신학회논문지
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• 제35권8A호
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• pp.760-767
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• 2010

For complex channel blind equalization, this study presents the performance and characteristics of two complex blind information theoretic learning algorithms (ITL) which are based on minimization of Euclidian distance (ED) between probability density functions compared to constant modulus algorithm which is based on mean squared error (MSE) criterion. The complex-valued ED algorithm employing constant modulus error and the complex-valued ED algorithm using a self-generated symbol set are analyzed to have the fact that the cost function of the latter forces the output signal to have correct symbol values and compensate amplitude and phase distortion simultaneously without any phase compensation process. Simulation results through MSE convergence and constellation comparison for severely distorted complex channels show significantly enhanced performance of symbol-point concentration with no phase rotation.

• 한국산업정보학회논문지
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• 제22권1호
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• pp.41-51
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• 2017

This Paper Describes a Method for the Evaluation of Sleep Apnea, Namely, the Peak Signal-to-noise ratio (PSNR) of Wavelet Transformed Electroencephalography (EEG) Data. The Purpose of this Study was to Investigate EEG Properties with Regard to Differences between Sleep Spindles and K-complexes and to Characterize Obstructive Sleep Apnea According to Sleep Stage. We Examined Non-REM and REM Sleep in 20 Patients with OSA and Established a New Approach for Detecting Sleep Apnea Base on EEG Frequency Changes According to Sleep Stage During Sleep Apnea Events. For Frequency Bands Corresponding to A3 Decomposition with a Sampling Applied to the KC and the Sleep Spindle Signal. In this Paper, the KC and Sleep Spindle are Ccalculated using MSE and PSNR for 4 Types of Mother Wavelets. Wavelet Transform Coefficients Were Obtained Around Sleep Spindles in Order to Identify the Frequency Information that Changed During Obstructive Sleep Apnea. We also Investigated Whether Quantification Analysis of EEG During Sleep Apnea is Valuable for Analyzing Sleep Spindles and The K-complexes in Patients. First, Decomposition of the EEG Signal from Feature Data was Carried out using 4 Different Types of Wavelets, Namely, Daubechies 3, Symlet 4, Biorthogonal 2.8, and Coiflet 3. We Compared the PSNR Accuracy for Each Wavelet Function and Found that Mother Wavelets Daubechies 3 and Biorthogonal 2.8 Surpassed the other Wavelet Functions in Performance. We have Attempted to Improve the Computing Efficiency as it Selects the most Suitable Wavelet Function that can be used for Sleep Spindle, K-complex Signal Processing Efficiently and Accurate Decision with Lesser Computational Time.

• 한국인터넷방송통신학회논문지
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• 제15권4호
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• pp.119-125
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• 2015

본 논문에서는 다중 셀 MIMO (multiple-input and multiple-output) 네트워크를 위한 Hadamard 행렬 인터스트림 (interstream) 전송기반 blind 채널추정을 소개한다. 제안 방법은 다중 셀로 된 이동 단말 네트워크를 기반으로 연구된다. MS (mobile station) 는 양 셀로부터 신호를 받는 것으로 가정한다. 가까운 셀로부터 받은 신호는 원하는 신호로 간주되고, 다른 셀로부터 받은 신호는 간섭신호로 간주된다. 채널은 blind이기 때문에 채널을 추정하기 위해 Hadamard 행렬 패턴의 파일럿 (pilot) 스트림 (stream) 을 전송하면, 대규모 MIMO 채널에 대해 보다 쉽고 빠른 채널 추정이 가능하게 된다. Hadamard 행렬 기반시스템의 계산은 오직 복소 가산 (complex addition) 만 필요하기 때문에, 복소 승산 (complex multiplication) 이 필요한 Fourier 변환을 이용한 방법보다 복잡도가 훨씬 줄어든다. 수치적 분석을 통해 본 결과 제안한 방법이 완벽함을 보여준다.