• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.47-52
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• 2006

In recent years, there is a strong urge to introduce GPS systems which can role in reference points and measure global positions to the field of structural measurements. In this study, a new structural measurement system using low-cost L1 single frequency GPS receivers instead of conventional expensive RTK L1&L2 dual frequency GPS receiver. This system consists of GPS OEM board, GPS antenna, wireless access points, and monitoring program based on Lambda method and makes it possible to apply to monitor a static behavior of large scaled Infra-structures, such as dams, tall buildings, road slops.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.8
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• pp.765-772
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• 2006

The L2 Civil Signal (L2CS) will be transmitted by modernized IIR(IIR-M), IIF and all subsequent GPS satellites. It contains two codes of different length; CM code contains 10,230chips, repeats every 20milliseconds and is modulated with message data, and CL code contains 767,250chips, repeats every 1.5second Z-count and has no data modulation. And the message data is encoded for Forward Error Correction(FEC). The long code length is useful for weak signal, but it also requires very long acquisition time. Therefore, the structure of GPS Ll/L2C Correlator and the fast acquisition scheme are proposed in this paper.

• Journal of IKEEE
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• v.24 no.2
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• pp.649-653
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• 2020

GPS is a representative satellite navigation system that provides users with accurate location and time information. GPS L1 C / A is opened for civilian and thus utilized in various fields. When the satellite signal reaches the receiver, signal acquisition unit of the digital signal processing hardware searches and acquires the signal among visible satellites. The signal acquisition unit has different implementation methods depending on the signal searching method, such as serial search acquisition, parallel frequency search, parallel code phase search. In this paper, we compare and analyze the three representative acquisition hardwares using live GPS L1 C/A signals. According to the comparison, the parallel code phase search acquisition outperforms the other methods due to reduction of the number of the searchings and a high resolution.

• 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 Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.167-173
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• 2006

Ionosphere is the largest error source on propagation of GPS signals. Dual frequency (L1,L2) GPS receiver can be effectively able to eliminate the ionosphere error by using linear combination of two frequencies, but the single frequency receiver (L1) have to compute the ionosphere error. In this research, we developed the new ionospheric model with $1^{\circ}$ by $1^{\circ}$ spatial resolution based on the grid from using 9 GPS reference stations which have been operated by KASI (Korea Astronomy and Space Science Institute) and computed TEC (Total Electron Contents) over South Korea by epoch. This paper gives the positioning results of Klobuchar model with that of a newly developed KASI regional ionospheric model and shows the positioning precision of the KASI regional ionospheric model along with TEC variation of ionosphere.

• Journal of Advanced Navigation Technology
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• v.17 no.2
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• pp.177-182
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• 2013

In this paper, printed antenna which can be applied to a built-in wireless module of the security controller operating at global positioning system(GPS) L1 frequency band(1.575GHz) is proposed. The proposed antenna is basically composed of a microstrip patch antenna with inserting feed. In particular left and right slots which are respectively asymmetric are used for impedance matching, whereas slot with one open-end and shorting point are used on the bottom plane to set operating frequency and enhance bandwidth. It is observed at the desired GPS L1 frequency band that the radiation efficiency and gain of the proposed antenna are 90% and more than 4.8dBi respectively.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.421-422
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• 2008

In this paper, CMOS RF front-end circuits for an L1/L5 dual-band global positioning system (GPS)/Galileo receiver are designed in $0.13\;{\mu}m$ CMOS technology. The RF front-end circuits are composed of an RF single-to-differential low noise amplifier, an RF polyphase filter, two down-conversion mixers, two transimpedance amplifiers, a IF polyphase filter, four de-coupling capacitors. The CMOS RF front-end circuits provide gains of 43 dB and 44 dB, noise figures of 4 dB and 3 dB and consume 3.6 mW and 4.8 mW from 1.2 V supply voltage for L1 and L5, respectively.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.7
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• pp.644-650
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• 2005

The expected positioning accuracies of civil users utilizing modernized GPS and Galileo are derived using the error analysis in this paper. Since, in general, the performance of DLL, PLL and FLL is proportional to chip lengths and wavelengths, the positioning accuracies from various measurements of modernized GPS and Galileo are derived as function of chip length and wavelength. These results are compared with that from GPS Ll measurement. In absolute positioning, compared to GPS C/A code only case, more than 17 times performance improvement is expected when all civil code signals of modernized GPS and Galileo (L1, L2, L5, E1, E5A and E5B) are used. In relative positioning, compared to GPS L1 carrier phase only case, more than 2 times performance improvement is expected when all civil signals of modernized GPS and Calileo are used. Furthermore, the relationship between GDOP and RGDOP in single frequency case is expanded to general case where multiple frequencies and both code and carrier phase measurements are used.

• Journal of Positioning, Navigation, and Timing
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• v.1 no.1
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• pp.29-34
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• 2012

A software GNSS signal generator for the GPS L1/L2/L5 and Galileo E1/E5 signals is proposed in this paper. And this signal generator is designed and implemented with several components by considering the reuse and expansion of components for similar GNSS signals. The characteristics of the reusability of the components are confirmed with the carrier generation and the band-pass filter components. And the functionality of the GNSS multi-band IF signal generator is validated by using the commercial software GPS L1 receiver, and the performance of signal acquisition, tracking and accuracy of horizontal position error are analyzed for this validation. As a result, the GPS L1 signal generator operates successfully and it could be expected that other signal generators also operate well because most of components are the same as those of the GPS L1 signal generator.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.2
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• pp.10-15
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• 2011

본 논문은 위성항법신호감시국용 GPS/갈릴레오 복합수신기에 대한 구현 및 성능 시험결과를 기술한 논문으로 복합수신기는 단일 플랫폼에서 갈릴레오 E1, E5a 신호와 GPS L1, L2C, L5 신호를 수신처리 할 수 있으며, GPS신호와 갈릴레오 E1 신호를 복합적으로 처리함으로써, 위치정확도가 향상됨을 보였다. 각 신호에 대한 신호획득을 신속하게 하기 위해, 모든 신호에 대해 정합필터와 FFT 방식이 결합된 방식을 적용하였고, 신호추적과정에서는 다수의 추적루프를 적용하였으며 본 논문에서는 주요 신호에 대한 신호획득 및 추적과정의 시험결과를 보였다. 또한 기존에 발표된 논문과의 차별화 항목으로, 항법신호의 수신레벨이 낮아 CW 형태와 같은 간섭신호에도 영향을 받는바, 이에 대한 개발된 항재밍 모듈에 대한 시험결과도 제시하였으며, 성능측면에서의 비교를 위해 상용수신기와 개발된 수신기와의 성능 비교 결과도 함께 제시하였다.