• 제어로봇시스템학회논문지
• /
• 제18권5호
• /
• pp.502-508
• /
• 2012

Heliostat, as a concentrator to reflect the incident solar energy to the receiver, is the most important system in the tower-type solar thermal power plant since it determines the efficiency and ultimately the overall performance of solar thermal power plant. Thus, a good sun tracking ability as well as a good optical property of it are required. Heliostat sun tracking system uses usually an open loop control system. Thus the sun tracking error caused by heliostat's geometrical error, optical error and computational error cannot be compensated. Recently use of sun tracking error model to compensate the sun tracking error has been proposed, where the error model is obtained from the measured ones. This work is a development of heliostat sun tracking error measurement and compensation method using BCS (Beam Characterization System). We first developed an image processing system to measure the sun tracking error optically. Then the measured error is modeled in linear polynomial form and neural network form trained by the extended Kalman filter respectively. Finally error models are used to compensate the sun tracking error. We also developed the necessary image processing algorithms so that the heliostat optical properties such as maximum heat flux intensity, heat flux distribution and total reflected heat energy could be analyzed. Experimentally obtained data shows that the heliostat sun tracking accuracy could be dramatically improved using either linear polynomial type error model or neural network type error model. Neural network type error model is somewhat better in improving the sun tracking performance. Nevertheless, since the difference between two error models in compensation of sun tracking error is small, a linear error model is preferred in actual implementation due to its simplicity.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2006년도 한국우주과학회보 제15권1호
• /
• pp.129-132
• /
• 2006

한국항공대학교 우주시스템연구실에서는 나노급 위성인 HAUSAT-2 개발과 더불어 주요 탑재체인 동물 추적 시스템을 직접 연구 개발하고 있다. 동물 추적 시스템은 위성에 탑재되는 동물 추적 시스템 수신기와 동물 추적 송신기, 위성으로부터 수신된 신호를 해석하고 처리하는 지상국으로 구성되어 있다. 본 논문에서는 동물추적시스템의 전반적인 운용개념과 하드웨어 개발에 대하여 기술하며 데이터를 처리하기 위한 소프트웨어 알고리즘 및 도플러 편이(Doppler Shift)를 이용한 동물 위치 추정 알고리즘에 대하여 논한다.

• Journal of Communications and Networks
• /
• 제7권3호
• /
• pp.248-257
• /
• 2005

In this paper, we develop design procedures for carrier tracking loop for orthogonal frequency division multiplexing (OFDM) systems or other systems of blocked data. In such communication systems, phase error measurements are made infrequent enough to invalidate the traditional loop design methodology which is based on analog loop design. We analyze the degradation in the OFDM schemes caused by the tracking loop and show how the performance is dependent on the rms phase error, where we distinguished between the effect of the variance in the average phase over the symbol and the effect of the phase change over the symbol. We derive the optimal tracking loop including optional delay in the loop caused by processing time. Our solution is general and includes arbitrary phase noise apd additive noise spectrums. In order to guarantee a well behaved solution, we have to check the design against margin constraints subject to uncertainties. In case the optimal loop does not meet the required margin constraints subjected to uncertainties, it is shown how to apply a method taken from control theory to find a controller. Alternatively, if we restrict the solution to first or second order loops, we give a simple loop design procedure which may be sufficient in many cases. Extensions of the method are shown for using both pilot symbols and data symbols in the OFDM receiver for phase tracking. We compare our results to other methods commonly used in OFDM receivers and we show that a large improvement can be gained.

• 한국통신학회논문지
• /
• 제22권3호
• /
• pp.506-514
• /
• 1997

In this paper, we implement digital circuit of despreading delay lock loop for GPS receiver. The designed system consists of Epoch signal generator, two 13bit correlators which correlates the received C/A code and the locally generated C/A code in the receiver, the C/A code generator which generates C/A code of selected satellite, and the direct digital clock synthesizer which generates the clock of the C/A code generator to control the phase and clock rate, the clock controller, and the clock divider. The designed circuit has the function of the acquisition and tracking by the autocorrelation characteristics of Gold code. The controller generates each other control signals according to the correlation value. The designed circuit is simulated to verify the logic functional performance. By using the simulator STR-2770 that generates the virtual GPS signal, the deigned FPGA chip is verified the circuit performance.

• Journal of Positioning, Navigation, and Timing
• /
• 제10권2호
• /
• pp.91-102
• /
• 2021

In this paper, a fully reconfigurable Software Defined Radio (SDR) for multi-constellation and multi-frequency Global Navigation Satellite System (GNSS) receivers is presented. The reconfigurability with respect to the data structure, variability of signal and receiver parameters, and receiver's internal functionality is presented. The configuration file, that is modified to lead to an entirely different operation of the SDR in response to specific target signal scenarios, directly determines the operating characteristics of the SDR. In this manner, receiver designers can effectively reduce the effort to develop many different combinations of multi-constellation and/or multi-frequency GNSS receivers. Finally, the implementation of the presented fully reconfigurable SDR is included with the experimental processing results such as acquisition, tracking, navigation for the received signals in the realistic fields.

• 한국통신학회논문지
• /
• 제15권5호
• /
• pp.353-363
• /
• 1990

본 논문은 Data Bit Jitter(DBJ)가 Data 동기수신회로의 Bit Slip Rate(BSR) 에 미치는 영향에 관하여 고찰하였다. 특히 이 논문에서는 BSR치를 계산하는데 필요한 특성 jitter parameter 들을 부각시켰으며 또한 DBJ에 관한 새로운 규격설정을 제시하였다. 새로이 제시된 방법에 의하면 종래의 방법에 비하여 복잡해진 점은 있으나, 반면 보다 현실적이고 보다 더 정확하게 DBJ의 BSR에 관한 영향을 예측할 수 있는 장점이 있다고 생각된다. 새로이 제시된 방법에서는 수신기에 의존하는 parameter들이 부각되었으며 jitter spectrum의 각 부분(저주파, 고주파 부분등)에 대한 적절한 비중이 고려되었다.

• 대한전자공학회논문지TC
• /
• 제44권12호
• /
• pp.44-53
• /
• 2007

이 논문은 실외에서 실시간 적이고 안정적이며 정확도가 높은 위치 인식 정보 및 위치 기반 서비스 제공을 위한 복합 위치인식 알고리즘 개발에 초점을 둔다. 현재 사용 중인 위성 항법 시스템에 갈릴레오 위성 항법 시스템을 병행하여 사용할 경우 사용 주파수의 증가와 가시 위성의 증가로 전리층 오차 등 여러 가지 오차 요인을 줄일 수 있다. 따라서 더 이상 거리 오차는 위치 인식에서는 문제가 되지 않는다. 하지만 노이즈로인해 생기는 chips 등기 오차는 acquisition이나 tracking 지연 오차를 유발하게 되어 수신기의 성능을 저하시킨다. 이를 해결하기 위하여 이 논문에서는 고 정밀도 향상을 위한 correlator를 제안하여 수신기의 성능 향상에 그 목적이 있다.

• Journal of Positioning, Navigation, and Timing
• /
• 제12권1호
• /
• pp.75-81
• /
• 2023

In this study, we design an optimized Graphics Processing Unit (GPU)-based GNSS signal processing technique with the goal of designing and implementing a GNSS Software Defined Receiver (SDR) that can operate in real time all-in-view mode under multi-constellation and multi-frequency signal environment. In the proposed structure the correlators of the existing GNSS SDR are processed by the GPU. We designed a memory structure and processing method that can minimize memory access bottlenecks and optimize the GPU memory resource distribution. The designed GNSS SDR can select and operate only the desired GNSS or desired satellite signals by user input. Also, parameters such as the number of quantization bits, sampling rate, and number of signal tracking arms can be selected. The computing capability of the designed GPU-based GNSS SDR was evaluated and it was confirmed that up to 2400 channels can be processed in real time. As a result, the GPU-based GNSS SDR has sufficient performance to operate in real-time all-in-view mode. In future studies, it will be used for more diverse GNSS signal processing and will be applied to multipath effect analysis using more tracking arms.

• 제어로봇시스템학회논문지
• /
• 제14권9호
• /
• pp.963-968
• /
• 2008

A new method to deal with GPS indoor positioning by means of time synchronized switching GPS repeater has been developed by authors[1]. But the developed indoor positioning system has problems. Therefore, we proposed a method for indoor positioning using GNSS Repeater-Assisted. To solve the 3-dimensional user's position, the 4 or more retransmission antennas are needed in the previously proposed methods. If a GPS repeater periodically transmits the signal like as pseudollite, the information for assisting an acquisition and tracking can be informed to receiver. Then, the user position can be calculated using the induced weak signal. The advantage of the proposed algorithm is use of only 1 re-transmission antenna because the re-transmitted signal are not used for positioning but used for assisting an acquisition and tracking weak signals induced indoor. We analyze the propose algorithms through the experiment and performed the test of feasibility.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
• /
• pp.114-117
• /
• 2002

The airborne tracking radar is located in front of aircraft or missile and measures and tracks a target motion. The signal processor receives target signals from a receiver using A/D converters, and calculates the target motion, and transfers the data to the aircraft or missile control unit. Since the signal processing system is required to be lightweight and small size as well as high performance to calculate and analyze the received signal, we use high speed DSPs and SMD type components having low power consumption. In this paper, we describe the design concept of signal processing system of the airborne tracking radar.