• 한국위성정보통신학회논문지
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• 제10권3호
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• pp.38-43
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• 2015

본 논문에서는 소프트웨어로 검증된 GPS 신호생성 알고리즘을 FPGA 기반으로 구현함으로써 RF레벨에서 다중 위성신호를 실시간으로 생성 가능한 GPS 신호생성기에 대해 기술한다. 탑재된 신호생성 알고리즘은 궤도 및 환경 오차 모델을 반영하고 수신기 위치를 기반으로 위성 신호를 모의한다. GPS 신호생성기 하드웨어는 16개의 위성 신호를 실시간으로 생성할 수 있는 디지털보드와 IF Data를 RF 신호로 변환해주는 아날로그보드로 구성되어 있다. Windows 기반의 신호생성 시뮬레이터를 제어하는 소프트웨어를 통해 항법신호뿐만 아니라 기만신호, 재밍신호를 생성이 가능하며 GIS 화면위에서 수신기의 경로를 편집할 수 있는 시나리오 구성 기능이 제공된다. GPS 신호생성기는 성능은 상용수신기를 이용해 검증하였다. GPS 신호생성기를 이용한 응용 예로써 실내측위 시스템을 구성하고 시험하였으며 실내측위 시스템의 정확도를 개선하는 것은 추가적인 연구를 진행하고 있다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1234-1238
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• 2005

As the low power GPS signal is susceptible to interference, interference can seriously degrade the performance of GPS receiver. This paper designs a ANIEF(Adaptive Narrowband Interference Excision in Frequency domain) filter that removes narrow band interferences with low signal loss. This filter uses the pre-correlation technique and attempts to filter out the interference in the frequency domain. The interference excision performance of the designed filter is evaluated for various interferences using the ANIEF filter inserted GPS software receiver and the interference generator. Interferences considered in this paper are single-tone CWI(Continuous Wave Interference), multi-tones CWI, pulsed CWI, and swept CWI. The narrowband interference excision filter in frequency domain is very effective against various interferences and the strong interference with a simple structure. However, the signal power loss is unavoidable while transforming. In this paper, the hamming window and overlap technique are adopted to reduce the signal power loss. Finally, the interference excision performance and the reduced signal power loss of the ANIEF filter are shown.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.695-701
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• 2008

In this paper, we propose the efficient Doppler removal method using map-based partial-time common intermediate frequency removal technique. In the proposed algorithm, the 2-stage carrier removal process was used. First, the component of common intermediate frequency is removed. Next the component of Doppler was removed with averaging and approximation. For the evaluation of the proposed algorithm, The real-time software GPS L1 C/A-code receiver was implemented. When the proposed algorithms are used, 12 tracking channels with 3 track arm(early, prompt, late) is operated real-time on PC using a Intel Pentium-III 1.0GHz CPU. Also, the requirement of memory was less than 2Mbytes. The real-time software GNSS receiver using the proposed algorithms provides the navigation solution with below 10 meter rms error. Especially, in spited of using the various approximations for implementing the algorithms, the high sensitivity capability (able to track the weak signal with -159dBm) was achieved.

• Journal of Positioning, Navigation, and Timing
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• 제1권1호
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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.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.399-403
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• 2006

Software-based GNSS receivers have the great advantage in flexibility compared with conventional receivers. But it has some problems to processing IF level Signal RAW data, need long time to process long term data and TTFF is long because the process is too slow. So this time, we concentrated on the signal acquisition, and examined the speedup technique. Using this technique, the acquisition was speedup dramatically, and signal-to-noise ratio was improved.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2016년도 춘계학술대회
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• pp.22-25
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• 2016

해상에서의 선박 항해에 있어서 GPS와 같은 위성항법시스템에 대한 의존도가 매우 높다. 하지만 전파 교란 등과 같은 열악한 환경이 선박 주위에 가해질 경우 선박에 탑재된 GPS 수신기에서 위치를 추정할 수 없기 때문에 정상적인 항해가 어렵게 된다. 본 논문에서는 위와 같은 약한 전파 교란 환경을 가정하여 열악한 환경 내에서 GPS 수신기가 위치 추정 정확도는 열화되더라도 자신의 위치를 처음 파악하는 데 걸리는 시간인 TTFF(Time To First Fix)를 감소시켜 선박의 신속한 위치 계산을 위한 개략 위치 추정 기법을 설계하였다. 또한 열악한 신호 환경을 가정하여 진행된 실험에서 기존 GPS TTFF와의 비교를 통해 설계된 기법을 검증하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.291-295
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• 2006

As GPS equipments improve, one can acquire GPS data easily in the field. However, to obtain precise and accurate coordinates, post processing is additionally required and the processing needs high degree of skills. Besides, it is very common that we can't operate processing software in the field because required system environment is usually not prepared. The aim of this study is the development of internet-based GPS data processing service. For post processing, we use GIPSY developed by JPL. It has many advantages such as precise point positioning, which enables a rapid determination of receiver positions. The developed service in this study proceeds as following orders by interlocking GIPSY and internet service on a Linux platform: Users upload raw data files on the internet, then GIPSY runs automatically and then the user get the result in the field. We use an Apache Web Server as a hosting program and PHP is used in coding web pages.

• 한국항행학회논문지
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• 제18권5호
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• pp.429-436
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• 2014

본 논문에서는 의사위성과 GPS 위성 사이의 시각동기를 위한 세가지 동기 방안을 제안하고 시각동기 기법의 성능 분석에 필요한 의사위성 시각동기 오차요소에 대해 분석한다. 제시한 세가지 시각동기 방안으로는 의사위성 시각동기 스테이션 구축 방안, UTC(KRIS)의 시각정보원을 활용한 의사위성 시각동기 방안, GPS 시각용 수신기를 활용한 시각동기 방안이 있다. 또한 제안한 의사위성 시각동기 방안의 성능평가를 위한 시뮬레이션 구성을 위해 의사위성 시각동기 방안의 오차요소를 의사위성 및 기준 클럭의 오차, 전송선로에 의해 발생하는 오차, TIC에 의해 발생하는 오차, 클럭 동기 알고리즘에 의해 발생하는 오차로 구분하고 각 오차 요소를 분석하였다.

• Journal of Positioning, Navigation, and Timing
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• 제3권2호
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• pp.53-62
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• 2014

In the guided missile and unmanned vehicle system, the navigation system is one of the most important components. Recently, low-cost effective smart projectiles and guided bomb are being developed using MEMS based navigation system which has high-G, low-cost and small size. In this paper, locally developed MEMS based GPS/INS integrated navigation system will be introduced in comparison with the state of the art of MEMS based navigation system. And technical design and development method is described to satisfy the required performance of GPS receiver, MEMS inertial sensor assembly, navigation computer and software.

• 농촌계획
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• 제7권2호
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• pp.3-11
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• 2001

A portable GPS receiver and a navigation software were used to investigate land application practices of manure composts. The field investigation indicated that most of the land application of manure composts were observed before April. Plowing for incorporation of manure with soil were continued from the middle of April. The results also revealed that over 60% of the farms were within 1 km from livestock farms from which manure composts were transported. Most of the farms having land application were dry field rather than paddies, Some of fields located near livestock farms frequently experience over-application of manure composts. It seems to have been difficult to complete the investigation in this study without the Gps/navigation system. The GPS/navigation system will become an essential tool in field investigations such as ecological/environmental monitoring works that require repeated observation at a number of sites.