인공위성 RPPT 시스템을 위한 단순화된 직병렬 구조

학위논문(석사) --서울대학교 대학원 :전기. 컴퓨터공학부,2008.2.Maste

(The) relation between internet news use, political socialization and family communication

학위논문(석사) --서울대학교 대학원 :언론정보학과,2009.8.Maste

개에서 실험적으로 유발한 척수 손상에 대한 코티코스테로이드와 전침술의 효과

Thesis (master`s)--서울대학교 대학원 :수의학과 수의외과학전공,2001.Maste

전파간섭 영향분석 및 검출 알고리즘 개발을 위한 위성항법 전파간섭 시뮬레이터 설계

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2013. 2. 박찬국.Global Navigation Satellite System (GNSS) is an essential system for land, maritime, and air navigation. GNSS is also used as main source for time synchronization in financial transaction and electrical grid. In addition, location based service based on GNSS is commonly used for general population. GNSS-based applications are proliferating due to its accuracy, convenience and low cost. However, most people do not realize how vulnerable GNSS is and its vulnerability problem has not resolved even though dependency on GNSS is rapidly increasing. The motivation of this thesis is to find a possible solution for GNSS vulnerability, especially for aviation applications. A Ground Based Augmentation System (GBAS) is an enabling technology for aircrafts’ GNSS based precision approach by enhancing GNSS navigation performance. The GBAS is well designed to ensure navigation system’s accuracy, integrity, availability, and continuity in normal radio frequency environment. However, its use is limited when radio frequency interference (RFI) is present. Some of potential RFI sources can be mitigated or eliminated by controlling unintentional RFI sources around airport and by enforcing law to prevent sales and use of commercial privacy jammers. However, RFI detection, mitigation and characterization system is still required for contingency. In this thesis, research is carried out to examine interference detection parameters and to propose applicable detection algorithm for aviation application. After analyzing pre-correlation and post-correlation detection parameters’ characteristics, an interference detection algorithm is developed utilizing AGC gain and adaptive lattice IIR notch filter parameters considering these parameter’s strengths and weaknesses. The proposed interference detection and characterization algorithm is designed to be used even in excessive RFI environment which prevent GNSS signal acquisition and tracking. The proposed algorithm can detect and classify various interference signals and estimate their signal power. The performance of the algorithm was verified by Monte-Carlo simulation. In addition, MATLAB SIMULINK GNSS interference simulator was designed to assess interference impact on GNSS receiver performance and to characterize interference detection parameters. The designed GNSS interference simulator is a flexible simulation platform to generate GNSS signal data in various types of interference environment according to users’ needs. Therefore, the GNSS interference simulator acted as an essential tool for interference detection and characterization algorithm development. The proposed detection and characterization algorithm and the GNSS interference simulator will be used for interference mitigation and location algorithm research.Chapter 1.Introduction 1 1.1 Motivation and Background 1 1.2 Objectives and Contributions 3 1.3 Organization 3 Chapter 2. Ground Based Augmentation System 4 2.1 Introduction 4 2.2 GBAS Requirement 5 2.3 GBAS Integrity Monitoring System 8 2.4 GBAS Stability Test Results and Recommendations 10 Chapter 3. GNSS Radio Frequency Interference 13 3.1 Types of RF Interference 13 3.2 Personal Privacy Devices 15 3.3 Intentional Jamming 18 Chapter 4. Interference Detection Parameter Analysis 19 4.1 Introduction 19 4.2 AGC Gain 20 4.3 ADC Histogram Distribution 20 4.4 Adaptive Notch Filter Parameters 21 4.5 Frequency Domain Approach 21 4.6 Carrier-to-Noise Ratio 22 4.7 Summary 23 Chapter 5. RFI Detection and Characterization Algorithm Design 25 5.1 RFI Detection Parameter Selection for GBAS 25 5.2 AGC Gain 25 5.2.1 AGC Model 25 5.2.2 AGC Characterization 27 5.3 Adaptive Lattice IIR Notch Filter Parameters 29 5.3.1 Adaptive Lattice IIR Notch Filter 29 5.3.2 Interference Detection and Classification using Adaptive Lattic IIR Notch Filter Parameters 32 5.4 Interference Detection and Characterization Algorithm 33 5.5 Performance Evaluation of the Proposed Algorithm 34 Chapter 6. Simulator Design for RFI Impact Assessment on GNSS 37 6.1 Introduction 37 6.2 GNSS Interference Signal Model 38 6.3 GNSS Interference Simulator Design 40 6.3.1 GPS Signal Generation Module 41 6.3.2 Interference Signal Generation Module 45 6.3.3 Front-end Signal Processing Module 48 6.4 RF Interference Impact Assessment 49 Chapter 7. Conclusions 54 Bibliography 56 국문초록 60Maste

Design of GNSS Interference Simulator using MATLAB SIMULINK

proceedingsGround Based Augmentation System (GBAS) is an enabling technology for GNSS based precision approach. However, GBAS is vulnerable to radio frequency interference, so GNSS interference detection and mitigation is essential for safe aircraft operation based on GBAS. In this paper, a GNSS interference simulator is designed based on previously developed GPS L1 software simulator. The interference simulator can generate user specified interferences repeatedly, so it can be used for interference signal characterization and detection algorithm research. The simulator gets signal parameters from a user and generates GPS L1 signal, noise and interference signals. The generated signals are processed by band pass filter, AGC, and ADC module and saved in a binary file. The simulator can generate single-tone continuous wave interference, swept continuous wave interference and band limited white Gaussian noise. The simulated signal data was verified by theoretical evaluation of signal spectrum and used for interference effect assessment and interference detection and mitigation algorithm research. This simulation environment allows rapid modification and tuning of parameters during algorithm development.DAPA/ADD/NGR

The Design of the GPS L1 Software Simulator using MATLAB SIMULINK

As Global Navigation Satellite System(GNSS) becomes the primary means of navigation, many researchers are trying to develop more efficient and robust GNSS receiver algorithm. Currently, algorithm development with a software GNSS receiver is common among developers due to its cost-effectiveness and flexibility. In addition, developers are in need of a GNSS signal simulator to test the performance of receivers and evaluate new algorithms. In this paper, a 8 channel GPS L1 software simulator was designed using MATLAB SIMULINK. The simulator gets signal parameters from a user and generates 8 satellites signals and saves IF signal after band pass filtering and analog to digital converting. The simulated signal data was verified by theoretical evaluation of signal spectrum and a software GPS receivers acquisition and tracking results. This simulator will be used to generate weak signals to evaluate new software receiver algorithm.본 연구는 방위사업청과 국방과학연구소가 지원하는 국방 위성항법특화연구센터 사업의 일환으로 수행되었습니다

Study on Interference Localization using DRSS/AOA Integrated Method

In localization techniques, the estimation methods used for source localization are typically based on received signal strength (RSS), time of arrival (TOA), time-difference-of-arrival (TDOA), angle-of arrival (AOA), or their combinations. Despite of lower location accuracy with a small number of nodes in general, differential received signal strength (DRSS)-based localization is a cost-effective solution with low-complexity. Specifically, it is attractive because DRSS is readily available in most types of wireless systems, and does not require accurate knowledge of transmitter such as the transmitted power. In this paper, a hybrid localization method is proposed to achieve better location accuracy. The proposed localization scheme combines DRSS from the base stations with the AOA measurement from the reference stations. Numerical results show that the proposed DRSS/AOA integrated method gives better location accuracy than AOA only location, when the number of base stations is small.DAPA/ADD/NGR

Performance Analysis of GNSS Interference Detection Parameters

ProceedingsIn this paper, an adaptive lattice IIR notch filter is employed to track narrowband single-tone and swept continuous wave interference(CWI), and an interference detection method is proposed. The detection parameters are selected by using their unique characteristics, according to the type of received interference. The performance of the detection parameters is simulated for scenarios of GNSS signal in the presence of single-tone and swept CWI. The detection probability according to the power of the interference is perfect when jammer to signal ratio(JSR) of single-tone CWI is above than 15dB and JSR of swept CWI is above than 25dB.DAPA/ADD/NGR

Analysis of GPS signal acquisition algorithm for SDR

In Software-Defined GPS Receiver (SDR), GPS signal acquisition is a significant algorithm to identify the visible satellites. It also finds the code phase and Doppler frequency. After acquisition, the acquired code phase and Doppler frequency are transferred to a tracking loop as initial values to demodulate the navigation data. Acquisition time and detectable signal strength are depending on the performance of acquisition algorithm. In this paper, traditional GPS signal acquisition algorithms are analyzed and compared with the proposed GPS signal acquisition algorithm based on the combination of both coherent and noncoherent approaches. The proposed algorithm is verified by simulations. The results show that the proposed GPS signal acquisition algorithm gives about two times faster acquisition time than the conventional algorithm. In addition, the improved algorithm is more effective in the acquisition of weak signals.본 연구는 방위사업청과 국방과학연구소가 지원하는 국방위성항법특화연구센터 사업의 일환으로 수행되었습니다

Performance Analysis of Interference on the Software GPS Receiver

In this paper, the effect of interferences on the GPS weak signal is analyzed by the carrier to noise ratio(C/No) which is the ratio of the received carrier power level to the noise power level in a 1Hz unit. The C/No is an important parameter describing the performance of a GPS receiver and an indicator of the quality of the received signal. To receive the GPS weak signal, adaptive acquisition method using differential coherent integration is implemented to the software GPS receiver and FLL discriminator is applied to the signal tracking loop. The proposed algorithm is verified by simulation, and the effect of the interference on signal is provided by theoretical results of the carrier to noise ratio.본 연구는 방위사업청과 국방과학연구소가 지원하는 국방위성항법특화연구센터 사업의 일환으로 수행되었습니다