• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.221-228
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• 2009

We estimated the receiver and satellite differential code bias(DCB) based on the ionospheric total electron content(TEC) estimation method. The GPS network which has been operated by the Korea Astronomy and Space Science Institute(KASI) was designed to calculate TEC. The receiver and satellite DCB values were obtained from the weighted least square method with time interval for one hour. The results represented that the receiver DCB values are mostly varying within ${\pm}2m$ meter and are derived comparatively stable within three days. The estimated mean values of the satellite DCB show the maximum and minimum values of 4.09 nano-second(ns), -6.28ns respectively. We could detect great variations of TEC over 9 TECU difference at any time when the DCB sets were applied to TEC estimation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2307-2314
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• 2015

This paper focuses on the generation algorithm of BeiDou pseudorange correction (PRC) and simulation based performance verification for design of Differential Global Navigation Satellite System (DGNSS) reference station and integrity monitor (RSIM) in order to prepare for recapitalization of DGNSS. First of all, it discusses the International standard on DGNSS RSIM, based on the interface control document (ICD) for BeiDou, estimates the satellite position using satellite clock offset and user receiver clock offset, and the system time offset between Global Positioning System (GPS) and BeiDou. Using the performance verification platform interfaced with GNSS (GPS/BeiDou) simulator, it calculates the BeiDou pseudorange corrections , compares the results of position accuracy with GPS/DGPS. As the test results, this paper verified to meet the performance of position accuracy for DGNSS RSIM operation required on Radio Technical Commission for Maritime Services (RTCM) standard.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.4
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• pp.49-55
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• 2015

This paper explains major considerations for integrated GPS/GLONASS/BDS positioning, and then analyzes integrated GNSS positioning accuracies based on low-cost receivers in open-sky and poor reception environments. In an open-sky environment, horizontal RMSE of the integrated system positioning is about 1.2m. It shows improved result compared with single system positioning, the improvement ratio was 17-55%. In poor reception environments, we sometimes could not do positioning because the number of visible satellites gets below four. In an integrated positioning mode, the number of visible satellites was always higher than four, allowing us to find positions all the time. The horizontal RMSE of the integrated system positioning in poor reception environments is about 6.4m. Compared with single system positioning;the integrated system positioning shows better performance and the improvement ratio was 8-47% for the horizontal directions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1112-1115
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• 2016

Global Positioning System(GPS) is a useful system used in both civilian and military applications. However, the signal of GPS is susceptible to jamming attacks due to low receive sensitivity, since the signals come from the satellite located at over 20,000 km above the earth. In this paper, we have conducted a preceding research on a non-Foster matching circuit that efficiently matches an electrically ultra-small GPS antenna. Electrically Small Antennas(ESAs) are inefficient radiators and are difficult to match in wideband due to extremely high quality factor. In order to match small GPS antenna in wideband, a non-Foster matching circuit for a small GPS antenna was designed. A negative impedance converter circuit consisting of Linvill's cross-coupled pair transistors was fabricated and its stability was verified by the time-domain stability analysis. In addition, anechoic chamber measurements show that the non-Foster matching circuit for small GPS antenna can lead bore-sight gain improvement by more than 17 dB.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.21 no.4
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• pp.309-316
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• 2003

Rapid and accurate data processing is required in many GPS(Global Positioning System) applications including surveying. While one can use four different kinds of GPS satellite orbits, we evaluated the accuracy and precision of each kind of orbits to find the best candidate for rapid and accurate data processing. The four different kinds of orbits we: broadcast orbits from GPS satellites; and ultra-rapid orbits, rapid orbits, and precise orbits provided by international GPS data analysis centers such as IGS. With GIPSY and ultra-rapid orbits, we could get the positioning accuracy of 1.5cm from seven days of GPS data. From this study, we conclude that rapid and accurate data processing is achieved with GIPSY and ultra-rapid orbits.

• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.29-35
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• 2013

In this paper, we investigate the type and detection methode of spoofing attack, and then analyze the performance of spoofing detection algorithm in GPS L1 signal through the simulation. Generally spoofer is different from the jammer, because the receiver can be operated and not. In case of spoofing the GPS receiver is hard to recognize the spoofing attack and can be operated normally without stopping because the spoofing signal is the mimic GPS signal. To evaluate the performance of spoofing detection algorithm, both the software based spoofing and GPS signal generator and the software based GPS receiver are implemented. In paper, we can check that spoofing signal can affect to the DLL and PLL tracking loop because code delay and doppler frequency of spoofing. The spoofing detection algorithm has been implemented using the pseudorange, signal strength and navigation solution of GPS receiver and proposed algorithm can effectively detect the spoofing signal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1520-1525
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• 2009

In this paper, we study and simulate the suggested position control system using GPS and USN to replace the existing control system of a crane. For the correct approach, the position control system of a crane is divided into the control system of the ground station and the mobile station The hardware is comprised of GPS receiving module to receive the position control data of a crane from GPS satellites, bluetooth communication module for the data communication between the ground station and the mobile station, supersonic sensor module for a precise position control of a crane, motor to replace a crane roller, embedded MCU(ATmega128L) and so on. In here, an embedded MCU controls GPS receiving module, bluetooth communication module and supersonic sensor module. The Software is comprised of three programs. Three programs are the program to filter GGA output part in a receiving data of GPS receiving module, the driving program for supersonic sensor module, the digital map program to monitor a crane location. From the simulation results, it is demonstrated that the proposed system has the capability of crane position control with 1cm precision.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.10
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• pp.2059-2064
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• 2011

The DGPS systems that is a GPS augmentation system were installed for ocean- and land-service. The ocean-based reference station of 11 site and the land-based reference station of 6 sites are operating for ocean- and land-service. Although the land-based reference stations provide the output power of 500W, the service shadow regions are occurred due to mountain lands and building area. In this paper, the service coverages for land-based reference stations are analyzed in conditions of output power enhancements of reference station. The service shadow areas are deduced from service coverages of land-based reference stations and ocean-based reference stations. The medium frequency-band wave propagation models are considered as DGPS wave propagation model. The service coverages are analyzed by considering the compensated ground surface-conductivity.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.64-68
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• 2007

This paper describes the development of RF front.end equipment of a wide band high precision satellite navigation receiver to be able to receive the currently available GPS navigation signal and the GALILEO navigation signal to be developed in Europe in the near future. The wide band satellite navigation receiver with high precision performance is composed of L - band antenna, RF/IF converters for multi - band navigation signals, and high performance baseband processor. The L - band satellite navigation antenna is able to be received the signals in the range from 1.1 GHz to 1.6 GHz and from the navigation satellite positioned near the horizon. The navigation signal of GALILEO navigation satellite consists of L1, E5, and E6 band with signal bandwidth more than 20 MHz which is wider than GPS signal. Due to the wide band navigation signal, the IF frequency and signal processing speed should be increased. The RF/IF converter has been designed with the single stage downconversion structure, and the IF frequency of 140 MHz has been derived from considering the maximum signal bandwidth and the sampling frequency of 112 MHz to be used in ADC circuit. The final output of RF/IF converter is a digital IF signal which is generated from signal processing of the AD converter from the IF signal. The developed RF front - end has the C/N0 performance over 40dB - Hz for the - 130dBm input signal power and includes the automatic gain control circuits to provide the dynamic range over 40dB.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.328-333
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• 2012

Current differential GPS (DGPS) system consists of reference station (RS), integrity monitor (IM), and control station (CS). The RS computes the pseudorange corrections (PRC) and generates the RTCM messages for broadcasting. The IM receives the corrections from the RS broadcasting and verifies that the information is within tolerance. The CS performs realtime system status monitoring and control of the functional and performance parameters. The primary function of a DGPS integrity monitor is to verify the correction information and transmit feedback messages to the reference station. However, the current algorithms for integrity monitoring have the limitations of integrity monitor functions for satellite outage or anomalies. Therefore, this paper focuses on the detection and identification methods of satellite anomalies for maritime DGPS RSIM. Based on the function analysis of current DGPS RSIM, it first addresses the limitation of integrity monitoring functions for DGPS RSIM, and then proposes the detection and identification method of satellite anomalies. In addition, it simulates an actual GPS clock anomaly case using a GPS simulator to analyze the limitations of the integrity monitoring function. It presents the brief test results using the proposed methods for detection and identification of satellite anomalies.