• 제어로봇시스템학회논문지
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• 제15권6호
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• pp.649-654
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• 2009

In this paper, an frequency tracking algorithm for weak signal tracking is proposed. The proposed frequency tracking algorithm uses a FMS (Fast Minus Slow) discriminator for frequency error estimation. This frequency tracking algorithm shows good frequency estimation performance under weak signal condition and is a computationally efficient for embedded software GNSS receiver. The software GNSS receiver implementing the proposed weak signal tracking algorithms could track GPS signal down to - 159dBm signal strength in the signal generator test and real GPS signal under dense urban condition.

• 제어로봇시스템학회논문지
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• 제17권3호
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• pp.283-288
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• 2011

In this paper, an adaptive signal tracking loop for a GPS L1/L2C/L5 receiver is designed. The design parameters is adjusted according to the receiver's operating conditions such as the signal strength and the receiver dynamics by using the different characteristics of GPS L1, L2C and L5 signal. Simulation results show that the tracking accuracy of the proposed signal tracking loop is better than those of L1, L2C and L5 only signal tracking loop.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.223-228
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• 2006

The main purpose of this paper is to describe the code tracking performance of a non-coherent digital delay lock loop (DLL) or coherent DLL while tracking GNSS signal in the presence of signal masking. The masking effect is usually caused by buildings that obscure the signal in either a periodic or random manner. In some cases, ideal masking is used to remove random or periodic interference. Three types of the masked signal are considered - no masking, periodic masking, and random masking of the signal input to the receiver. The mean time to lose lock (MTLL) of the code tracking loop are evaluated, and some numerical result and simulation results are reported. Finally, the steadystate tracking errors on the performance of the tracking loop in interference environment are also presented.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.15-22
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• 2006

This paper presents a novel signal tracking algorithm for GNSS receivers using a MLE technique. In order to perform a robust signal tracking in severe signal environments, e.g., high dynamics for navigation vehicles or weak signals for indoor positioning, the MLE based signal tracking approach is adopted in the paper. With assuming white Gaussian additive noise, the cost function of MLE is expanded to the cost function of NLSE. Efficient and practical approach for Doppler frequency tracking by the MLE is derived based on the assumption of code-free signals, i.e., the cost function of the MLE for carrier Doppler tracking is used to derive a discriminator function to create error signals from incoming and reference signals. The use of the MLE method for carrier tracking makes it possible to generalize the MLE equation for arbitrary codes and modulation schemes. This is ideally suited for various GNSS signals with same structure of tracking module. This paper proposes two different types of MLE based tracking method, i.e., an iterative batch processing method and a non-iterative feed-forward processing method. The first method is derived without any limitation on time consumption, while the second method is proposed for a time limited case by using a 1st derivative of cost function, which is proportional to error signal from discriminators of conventional tracking methods. The second method can be implemented by a block diagram approach for tracking carrier phase, Doppler frequency and code phase with assuming no correlation of signal parameters. Finally, a state space form of FLL/PLL/DLL is adopted to the designed MLE based tracking algorithm for reducing noise on the estimated signal parameters.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.128-128
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• 2000

An antenna tracking technique, referred to as "step track", is commonly used in communication applications. In this paper, an algorithm to improve the step-tracking technique for satellite tracking is proposed. We suggest a method by which the antenna scans the azimuth, detects the satellite signal without the position information, and points quickly to the direction receiving the signal of peak level. After reaching the peak level, the step-track system maintains enough signal levels to receive satellite broadcasting normally. Performance of the Tracking Algorithm proposed in this paper are verified with simulation.

• Journal of Positioning, Navigation, and Timing
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• 제10권4호
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• pp.307-313
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• 2021

Modernized GNSS signal structures tend to use tiered codes, and all GNSSs use binary codes as secondary codes. However, recently, signals using polyphase codes such as Zadoff-Chu sequence have been proposed, and are expected to be utilized in GNSS. For example, there is Tiered Differential Polyphase Code (TDPC) using polyphase code as secondary code. In TDPC, the phase of secondary code changes every one period of the primary code and a time-variant error is added to the carrier tracking error, so carrier tracking ambiguity exists until the secondary code phase is found. Since the carrier tracking ambiguity cannot be solved using the general GNSS receiver architecture, a new receiver architecture is required. Therefore, in this paper, we describe the carrier tracking ambiguity and its cause in signal tracking, and propose a receiver structure that can solve it. In order to prove the proposed receiver structure, we provide three signal tracking results. The first is the differential decoding result (secondary code sync) using the general GNSS receiver structure and the proposed receiver structure. The second is the IQ diagram before and after multiplying the secondary code demodulation when carrier tracking ambiguity is solved using the proposed receiver structure. The third is the carrier tracking result of the legacy GPS (L1 C/A) signal and the signal using TDPC.

• 한국인터넷방송통신학회논문지
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• 제20권5호
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• pp.71-77
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• 2020

최근 추적 레이더는 다양한 환경에서 여러 가지 제약을 받지 않고 운용이 가능한 소형 추적 레이더 개발의 필요성을 확인하였다. 또한 소형 추적 레이더의 성능은 기존 추적 레이더와 동등 이상을 요구한다. 이런 소형 추적 레이더는 기존 추적 레이더의 소형화와 저전력화를 통해 구현할 수 있다. 본 논문에서는 소형 추적 레이더를 위한 신호처리기의 역할과 기능을 정의하고, 소형 추적 레이더를 위한 신호처리기를 구현하기 위해 필요한 디바이스 사용의 최소화를 통한 소형화와 소비 전력의 효율을 높이기 위한 방안을 제안하였다. 소형화에 대한 방안으로 상용 DDC, 통신 controller등의 디바이스 기능을 FPGA에 구현하여 소형 추적 레이더를 위한 신호처리기를 설계하였다. 또한 효율이 좋은 Switching regulator를 사용한 전원부의 설계로 저전력 신호처리기를 설계하였다. 마지막으로 구현한 소형 추적 레이더를 위한 신호처리기의 성능시험과 소형 추적 레이더에 신호처리기를 적용한 도플러 추적 시험, 거리 추적 시험으로 신호처리기를 검증하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.285-289
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• 2006

In this paper, a design and implementation of GPS/Galileo software receiver is given. As a GPS receiver, it is able to perform every function of receiver such as acquisition, code and carrier tracking, navigation bit extraction, navigation data decoding, pseudorange calculations, and position calculations. A method to acquire and track the Galileo BOC(1,1) signal is also required because the correlation of BOC(1,1) signal has multiple peaks different from that of GPS signal. Therefore, a method to detect the main-peak in correlation function of BOC signal is required to avoid false acquisition. In this paper, very-early, very late correlation is implemented to track the correct main peak. The performance of implemented GPS/Galileo software receiver with BOC(1,1) signal tracking feature is evaluated with GPS/Galileo IF signal generator.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2002년도 종합학술발표회 논문집 Vol.12 No.1
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• pp.118-122
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• 2002

This paper is concerned with the design of the beam forming module that is a key unit of the active phased array antenna(APAA) system for mobile satellite communications. This module includes two blocks for main signal and tracking signal. Main signal block has the role of transmitting input signal from phased away antenna to tracking signal block. And, tracking signal block executes main roles, beam forming of tracking signal and electronic beam control. The several electrical performances of this module, phase characteristics and linear gain, etc., agreed with specifications needed for APAA, and for more clear verification of the performances, the satellite communication test of the APAA including the modules was accomplished in the outdoors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.669-672
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• 2003

This paper proposes a tracking algorithm for receiving satellite signal. Tracking algorithm uses the angular velocity of vehicle and the slope of received satellite signal for searching the maximum level of signal. The tracking algorithm is composed of two parts. One is the routine to maintain the acceptable signal in spite of the variation of angular velocity. The other is the fine tuning routine to search the maximum signal level by giving the weight factors to the slope of signal. Experimental results show that the proposed algorithm is efficient and stable.