• Journal of Positioning, Navigation, and Timing
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• 제3권3호
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• pp.107-116
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• 2014

When an incoming Global Positioning System (GPS) signal is acquired, pull-in search performs a finer search of the Doppler frequency of the incoming signal so that phase lock loop can be quickly stabilized and the receiver can produce an accurate pseudo-range measurement. However, increasing the accuracy of the Doppler frequency estimation often involves a higher computational cost for weaker GPS signals, which delays the position fix. In this paper, we show that the Doppler frequency detectable by a long coherent auto-correlation can be accurately estimated using a complex-weighted sum of consecutive short coherent auto-correlation outputs with a different Doppler frequency hypothesis, and by exploiting this we propose a noise resistant, low-cost and highly accurate Doppler frequency and phase estimation technique based on a reverse directional application of the finite rate of innovation (FRI) technique. We provide a performance and computational complexity analysis to show the feasibility of the proposed technique and compare the performance to conventional techniques using numerous Monte Carlo simulations.

• 대한전자공학회논문지TC
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• 제44권5호
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• pp.40-46
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• 2007

본 논문에서는 OFDM(Orthogonal Frequency Division Multiplexing) 기반의 트랜스패런트(transparent) 이동 다중 홉 릴레이(mobile multi-hop relay; MMR)시스템에서 MS(Mobile Station)가 이동함에 따라 발생하는 도플러 확산(Doppler spread)에 대한 영향을 분석한다. 상호협력(cooperative) MMR 또는 비상호협력(non-cooperative) 수율 증가(throughput enhancement;TE) MMR을 갖는 OFDM 시스템에서 부채널간 간섭(interchannel interference; ICI) 전력과 ICI 전력의 상계(upper bound)를 유도한다. 또한, 신호 대 간섭비(signal-to-interference ratio; SIR)와 SIR의 하계(lower bound)를 유도하고, WiBro(mobile WiMAX)용 파라미터를 이용하여 모의 실험을 통해 유도 결과를 검증한다.??

• International Journal of Computer Science & Network Security
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• 제23권5호
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• pp.121-127
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• 2023

A 500 km/h linear motor high speed terrestrial transportation service is planned to launch 2027 in Japan. In order to support 5G service in the train, the Sub-carrier spacing frequency of 30 kHz is planned to be used instead of common 15 kHz sub-carrier spacing to mitigate Doppler effect in such high-speed transportation. In addition, to increase the cell size of 5G mobile system, plural Base Station antenna will transmit the identical Down Link (DL) signal to form the expanded cell size along the train rail. In this situation, forward and backward antenna signals will be Doppler shifted by reverse direction respectively and the receiver in the train might suffer to estimate accurate Channel Transfer Function (CTF) for its demodulation. In this paper, Delay and Doppler Profiler (DDP) based Channel Estimator is proposed and it is successfully implemented in signal processing simulation system. Then the simulated performances are compared with the conventional Time domain linear interpolated estimator. According to the simulation results, QPSK modulation can be used even under severe channel condition such as 500 km/h, 2 path reverse Doppler Shift condition, although QPSK modulation can be used less than 200 km/h with conventional Channel estimator.

• 한국정보통신학회논문지
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• 제11권3호
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• pp.452-458
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• 2007

비교적 낮은 고도에서의 기상위험 탐지를 위한 항공기용 기상 레이다의 경우 강력한 지표면 반사파가 존재하게 되며 이러한 강력한 클러터의 제거 없이는 미약한 도플러 신호로부터 신뢰성 있는 기상 자료의 추출이 불가능하다. 그러나 시스템 위상잡음은 클러터 및 도플러 신호를 분산시켜 효율적인 클러터 제거에 심각한 문제를 일으킬 수 있다. 따라서 본 논문에서는 도플러 기상 레이다 시스템에서의 위상잡음을 모델링하고 이에 따른 클러터 및 신호에 미치는 영향 정도를 구체적으로 분석할 수 있도록 하였다. 또한 수신되는 클러터 및 도플러 신호전력의 비에 따른 위상잡음에 의한 클러터 전력 제거의 한계치를 고찰하였다. 수신되는 신호 대 클러터 비가 낮은 경우 상대적으로 강력한 클러터 전력의 위상잡음으로 인한 분산 현상으로 일정 정도 이상의 효율적인 클러터 제거가 어렵게 됨을 알 수 있다.

• 한국통신학회논문지
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• 제28권11C호
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• pp.1111-1117
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• 2003

이동 통신 시스템에서 이동체의 속도 추정은 수신신호의 최대 도플러 주파수를 찾는 과정이다. 하지만 실제적인 이동 통신 환경에서 이동체의 속도 추정은 부가된 잡음의 영향으로 많은 왜곡을 가지게 된다. 본 논문에서는 이동 통신 환경에서 최대 도플러 주파수 추정 시 부가 잡음의 영향을 억제하기 위한 결정 궤환 적응형 대역 제한(Decision Feedback Doppler Adaptive Band-Limit : DF-DABL) 알고리즘을 제안한다. 제안된 알고리즘에서는 잡음의 2차 통계 특성을 대역 제한 방법을 통하여 신호의 특성과 일치하게 함으로서 부가된 잡음의 영향을 효과적으로 제거한다. 특히 제안된 방법에서는 신호대잡음비 (SNR)와 같은 추가 채널 정보를 필요로 하지 않는다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.53-55
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• 2001

A dual probe laser Doppler vibrometer (LDV) that has one laser source and provides two independent object beams has been developed for the first time. An electronic circuit that converts light signal to electronic signal has been also developed using phase locked loop(PLL). It was found that this types of dual probe LDV can be used in differential mode and self-vibration compensation mode.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1838-1840
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• 2001

A dual probe laser Doppler vibrometer (LDV) that has one laser source and provides two independent object beams has been developed for the first time. An electronic circuit that converts light signal to electronic signal has been also developed using digital phase locked loop(DPLL). It was found that this types of dual probe LDV can be used in differential mode and self-vibration compensation mode.

• 한국군사과학기술학회지
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• 제3권1호
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• pp.58-65
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• 2000

A target signal simulation method for passive sonar systems is introduced. The method uses multirate signal processing techniques to simulate moving target signals in the multi-path sound propagation environment by introducing Lloyd's mirror and Doppler effect. Time and frequency variation of target signal due to the target maneuvering is also considered to provide realistic ship signatures in the LOFAR gram so that the simulated target is used for sonar operator training. Synthesized target characteristics is analyzed and compared with real target signal in terms of interference pattern and frequency variation in the LOFAR gram.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.158.2-158
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• 2001

This paper introduces the design and implementation of a signal processing system for an airborne active homing radar system. This airborne active homing radar system uses the pulse Doppler radar of high PRF (Pulse Repetition Frequency) for computation of exact relative velocity of the target. This system carries out two operations mainly. The first is to transmit and receive microwave signal through the antenna. The second is to calculate the relative velocity of the target taking advantage of the Doppler frequency signal reflected from the target and detect the angle error between a target and an antenna LOS (Line Of Sight) to make the antenna direction coincident with the target. The signal processing system has a role of the latter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2434-2437
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• 1999

In order to detect the ultrasonic that is generated by the partial discharge of the heavy electric machinery, a Laser Doppler Vibrometer (LDV) was developed. A Michelson type interferometer which employed heterodyne signal process technique was built to measure the frequency and amplitude of vibration. The output signal of the fast photodetector was a frequency modulated signal centered at 40 MHz. The signal from the detector was amplified and downconverted to intermediate frequency centered at 1 MHz after mixing process. The voltage output that was proportional to the velocity of the moving surface(PZT) was obtained using PLL. The spectrum of the FM signal was analyzed and integration method was introduced to obtain amplitude information. This LDV can be used to measure the vibration of MEMS devices, automobiles, HDD and CDP.