• Electronics and Telecommunications Trends
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• v.23 no.4
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• pp.137-146
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• 2008

위성항법수신기는 항법위성(GPS)들이 현재 위치와 시간이 담긴 전파신호를 지상으로 송신하면, 이런 신호를 받아 전파가 도달하기까지 걸린 시간을 계산해 자신의 현재 위치를 파악하게 된다. 경도와 위도, 높이를 동시에 파악하기 위해서는 3개 위성신호가 요구되고, 위성간 시간 오차를 제거해 위치 측정의 정확도를 높이기 위한 신호용으로 또 하나의 위성이 필요해 4개 위성이 요구된다. 항법의 형태는 육표기반 항법, 천체기반 항법, 센서기반 항법, 무선기반 항법 및 위성기반 항법으로 분류되며 그 중 전역이고 간섭 영향 및 재밍(jamming)이 어려우며 정확도 측면에서 우수한 위성항법시스템에는 GPS(미국), GLONASS(러시아)가 운용중이고, Galileo(유럽연합), COMPASS(중국), QZSS(일본), IRNSS(인도)이 개발중이다. 위성항법시스템 다원화에 따라 위성항법 수신기 기술도 이중주파수처리 및 타 시스템과의 호환성 제공이 요구되는바, 본 논문에서는 위성항법 수신기 기술 동향을 소개하고자 한다.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.1
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• pp.9-15
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• 2017

In this paper, results of a jammer detection and localization system operation are given. The system consists of receiver stations, a central tracking station, and a monitoring station and it was developed by our institute in 2014. Through real-time tests, it is confirmed that the developed system has an ability to estimate the location of interference sources with an accuracy of 50 m (CEP) even they was 10 km away. After verification, this system was installed in Incheon International Airport and operating results are being monitored by the airport and our institute continuously. In this year, there were some events that jamming signals were received from North Korea, so the data were analyzed and given here.

• Journal of Space Technology and Applications
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• v.2 no.2
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• pp.169-186
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• 2022

In this article, Russia's space threat assessment and space warfare in the Russia-Ukraine war (Russian invasion of Ukraine) were analyzed and summarized. Considering the probability that commercial satellites will also be potential targets of space warfare, it is suggested that not only military satellites but also commercial satellites develop and apply space technology that can be applied equally to space threats when developing space technology. Necessary space technologies is listed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1549-1556
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• 2016

By increased moving speed of aircraft, estimating location of itself becomes more important than ever. This requirement is satisfied by appearance of GPS, however it is useless when signal reception from satellite is not good enough by interruption, for example, traffic jamming. Applying link for communication to additional positioning system is capable of providing relative position of aircraft. Estimating location with link for communication is done without additional equipment but with signal processing based on correlation of received signal. ESPRIT is one of the representative algorithm among them. Estimating correlation matrix is possible to have error since it includes average operation needs enough number of samples not impractical. Therefore we propose algorithm that defines, estimates and removes error matrix of correlation. Proposing algorithm shows better performance than previous one when transmitters are close.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.2
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• pp.169-176
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• 2012

GPS(Global Positioning System) is widely used for the position estimation of an aerial vehicle. However, GPS may not be available due to hostile jamming or strategic reasons. A vision-based position estimation method can be effective if GPS does not work properly. In mountainous areas without any man-made landmark, a horizon is a good feature for estimating the position of an aerial vehicle. In this paper, we present a new method to estimate the position of the aerial vehicle equipped with a forward-looking infrared camera. It is assumed that INS(Inertial Navigation System) provides the attitudes of an aerial vehicle and a camera. The horizon extracted from an infrared image is compared with horizon models generated from DEM(Digital Elevation Map). Because of a narrow field of view of the camera, two images with a different camera view are utilized to estimate a position. The algorithm is tested using real infrared images acquired on the ground. The experimental results show that the method can be used for estimating the position of an aerial vehicle.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.3
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• pp.131-136
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• 2016

The present paper shows that beamforming algorithm such as Minimum Variance Distortionless Response (MVDR) based on array antenna signal processing can have not only anti-jamming but also anti-spoofing characteristics. A beam pattern due to the beamforming algorithm strengthens received signal power as it is formed in the incident direction of desired signal. During the process, the effect of unnecessary signals such as spoofing signals can be reduced because the beam pattern reduces received signal power in the incident directions excluding the beam pattern-directed direction. In order to analyze the anti-spoofing effect due to the beamforming algorithm, a software-based simulation environment was configured. An arbitrary error was applied between incident direction of Global Positioning System (GPS) satellite signal and steering vector direction of the beamforming algorithm to analyze the received signal power and required conditions were provided to see the anti-spoofing effect due to the beamforming algorithm. The used antenna was 7-element planar circular array and beam patterns were formed through the MVDR algorithm.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.58-63
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• 2007

GPS signal is vulnerable to intentional and unintentional interferences since it has a very weak signal power and its structure is well-known. Among the interference rejecting techniques, the ATF is being generally used as a pre-correlation technique. However, it does not have a design parameter relating to the notch width, resulting in the spectral loss around frequency of the interference. The IIR notch filter has a design parameter relating to the notch width and can generate a sharp notch for the CW interference. In this paper, an adaptive IIR notch filter is proposed and the performance is evaluated using software signal generator and real measurements.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.347-352
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• 2006

Narrowband interference can severely degrade the performance of GPS receivers. Detecting the presence of interference and then characterizing it can lead to its removal. Receivers can be reconfigured to focus on other signals or satellites that are less vulnerable to that interference at that moment. Using hardware reconfigurability of FPGA receivers and characterizing the effect of narrowband interference on the GNSS signal quality lead us to a new RFI mitigation technique in which the highest quality and less vulnerable signal can be chosen at each moment. In the previous work [1], the post processing capability of a software GPS receiver, has been used to detect and characterize the CW interference. This is achieved by passing the GPS signal and the interference through the correlator. Then, using the conventional definition of C/No as the squared mean of the correlator output divided by its variance, the actual C/No for each satellite is calculated. In this work, first the 'Exclusion zone' for each satellite signal has been defined and then by using some experiments the effects of different parameters like signal power, jamming power and the environmental noise power on the Exclusion zone have been analyzed. By monitoring the Doppler frequency of each satellite and using the actual C/No of each satellite using the traditional definition of C/No and actual data from a software GPS receiver, the decision to reconfigure the receiver to other signal can be made.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.4
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• pp.683-690
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• 2018

In this paper, a new signal processing technique is proposed for calibrating gain, phase, delay offsets in array antenna based anti-jamming minimum variance distortionless response (MVDR) global-positioning-system (GPS) receivers. The proposed technique estimates gain, phase and delay offsets across the antennas, and compensates for the offsets based on the estimates. A pilot signal with good correlation characteristics is used for accurate estimation of the gain, phase and delay offsets. Based on the cross-correlation, the delay offset is first estimated and then gain/phase offsets are estimated. For fine delay offset estimation and compensation, an interpolation technique is used, and specifically, the discrete Fourier transform (DFT) is employed for the interpolation technique to reduce the computational complexity. The proposed technique is verified through computer simulation using MATLAB. According to the simulation results, the proposed technique can reduce the gain, phaes and delay offset to 0.01 dB, 0.05 degree, and 0.5 ns, respectively.

• Smart Media Journal
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• v.7 no.3
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• pp.64-71
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• 2018

Utilization of unmanned aerial vehicles (UAVs) are rapidly expanding to various fields ranging from defense, industry, entertainment and personal hobbies. Due to the increased activities of unmanned airplanes, many security problems have emerged, including flight path errors to undesired destinations, secondary threats due to exposed securities caused by the capture of unmanned airplanes in hostile countries. In this paper, we find security vulnerabilities in UAVs such as GPS spoofing, hacking captured video information, malfunction due to signal attenuation through jamming, and exposure of personal information due to image shooting. In order to solve this problem, the stability of the unstructured data is secured by setting the encryption of the video shooting information section using the virtual private network (VPN) to prevent the GPS spoofing attack. In addition, data integrity was ensured by applying personal information encryption and masking techniques to minimize the secondary damage caused by exposure of the UAV and to secure safety. It is expected that it will contribute to the safe use and stimulation of industry in the application field of UAV currently growing.