• 한국군사과학기술학회지
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• 제12권2호
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• pp.182-190
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• 2009

GPS receivers can be disrupted by intentional or unintentional jamming, then it is unable to receive GPS signals and it is impossible to get the correct navigation results. Anti-jamming schemes using array antennas are being studied well due to high performance of those, and the efforts to apply them to GPS receiver are also being done. A GPS receiver structure for a multiple beam-forming scheme among those schemes has been proposed in this paper, and the performance is also compared with that using a general GPS receiver structure. For a general GPS receiver structure, each satellite signal which is formed by a beam-forming scheme is summed to be processed in a part of digital signal processing. For a proposed GPS receiver structure, however, each satellite signal is respectively processed by a designated channel in a part of digital signal processing. Finally, it is confirmed that the proposed GPS receiver structure is superior to a general GPS receiver structure in a point of the carrier to noise power ratio and the navigation accuracy using a software platform.

• 한국항행학회논문지
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• 제20권3호
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• pp.218-225
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• 2016

일반적으로 알려진 GPS 항재밍 기술로는 재밍 방향에 대한 감쇄효과를 얻는 널 스티어링 (null steering)과 위성방향으로의 추가 합성이득을 얻는 빔 스티어링 (beam steering) 방식이 있다. 이 신호처리 알고리즘을 소개하는 문헌에 의하면, 수학 공리에 따라 동시처리 가능한 재밍의 개수는 배열안테나 소자의 개수 N 에서 기준 안테나 1개를 제외한 N-1 개에 대해서만 유효하다는 표현을 하지만, 재머 배치나 비행체의 자세 그리고 둘 간의 상대적 배치 등 실질적인 운용 조건을 고려한 알고리즘 특성에 대한 분석은 알려져 있지 않다. 이에 본 논문에서는 4소자 및 7소자 표준 배열안테나가 적용된 항재밍 시스템을 모델링하여 비행체의 자세(수평, 수직)와 재머 배치, 그리고 안테나 소자 수를 고려한 두 항재밍 알고리즘(PM, LCMV)에 대한 성능 분석을 하였다. 결과적으로, 동일한 JSR 환경임에도 불구하고, 위성 신호와 재밍 신호 간 입사각이 상대적으로 큰 비행체의 수직 자세의 경우 수평 자세보다 약 10 dB 이상의 이득이 있음을 시뮬레이션을 통해 제시 하였다.

• 한국전자파학회논문지
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• 제25권6호
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• pp.628-636
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• 2014

본 논문은 재밍 대응 위성 항법 장치의 5소자 평면 배열 안테나 설계에 대해 기술한다. GPS $L_1/L_2$ 대역에서 공진하는 적층 구조의 패치 안테나 설계를 제안한다. 제안된 안테나는 광대역 및 원형 편파 특성을 구현하기 위해 칩 커플러를 이용한 이중 급전을 사용한다. 배열안테나 측정 결과, 중앙안테나의 전면 방향 이득은 $L_1$과 $L_2$ 대역에서 각각 1.10 dBic, 0.37 dBic, 측면안테나는 $L_1$과 $L_2$ 대역에서 0.99 dBic, -0.57 dBic를 갖는다. 고각 $30^{\circ}$에서 방위각의 이득은 중앙안테나 $L_1$과 $L_2$ 대역에서 평균 -2.08 dBic, -5.33 dBic의 측정 결과를 갖는다. 측면안테나는 $L_1$과 $L_2$ 대역에서 평균 -0.40 dBic, -2.09 dBic의 측정 결과를 갖는다. 제안된 5소자 평면 배열 안테나는 GPS 재밍 대응 장치에 적합함을 확인한다.

• Journal of Positioning, Navigation, and Timing
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• 제8권3호
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• pp.95-105
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• 2019

A method that applies space-time adaptive signal processing (STAP) algorithm based on an array antenna consisting of multiple antenna elements has been known to be effective to remove wide-band jamming signals in GPS receivers. However, the occurrence of phase distortion in navigation signals has been a problem when navigation signals, from which jamming signals are removed using STAP, are supplied to global positioning system (GPS) receivers. This paper verified the navigation performance degradation as a result of phase distortion. To mitigate this phenomenon, this paper proposes a mode switching scheme, in which a bypass mode is adopted to make the best use of the tracking performance of receivers without performing signal processing when jamming signals are not present or weak, and a STAP mode is employed when jamming signals exceed the threshold value. In this paper, the mode switching scheme is proposed for two environments: when receivers are stationary, and when receivers are moving. This paper confirmed that the performance of position error improved because phase distortion could be excluded due to STAP if the bypass mode was adopted under a condition where the jamming signal power level was below the threshold value in an environment where receivers were stationary. However, this paper also observed that the navigation failed due to the instability of tracking performance of receivers due to phase distortion that occurred at the switching time, although the number of switching could be reduced dramatically by proposing a dual threshold scheme of on- and off-thresholds that switched a mode due to the array antenna characteristics of varying gains according to the jamming signal incident direction in an environment where receivers were moving. The analysis results verified that running the STAP algorithm at all times is more efficient than the mode switching, in terms of maintaining stable navigation and ensuring position error performance, to remove jamming signals in an environment where receivers were moving.

• 한국군사과학기술학회지
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• 제9권3호
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• pp.48-55
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• 2006

This paper describes the antenna based GPS anti-jamming technology called CRPA(Controlled Reception Pattern Antenna), which used $2{\times}2$ array elements. In this system, the main functions are the antenna complex weight control and the GPS digital I/Q VM(Vector Modulator). To update the VM's I/Q complex weights, the PC based DAC(Digital to Analog Converter) module was also used and the two analog output voltages were applied to the $2{\times}2$ array elements to synthesize the null pattern. In the study, we also simulated the $2{\times}2$ GPS array null patterns to compare the null depth with experimental results. The VM was also modified at the frequency of 1.575GHz for the GPS L1 and controlled by the PC based VM software.

• Journal of Positioning, Navigation, and Timing
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• 제11권3호
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• pp.181-189
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• 2022

The public open signals from Global Navigation Satellite System (GNSS) including Global positioning system (GPS) are used widely by many peoples in the world except for the public regulated restriction signals which are encrypted. Nowadays there are growing concerns about GNSS signal spoofing which can deceive the GNSS receivers by abusing these open services. To counter these spoofing threats, many researches have been studied including array antenna techniques which can detect the direction of arrival by means of Multiple Signal Classification (MUSIC) algorithm. Originally the array antenna techniques were developed to countermeasure the jamming signal in electronic warfare by using the nulling or beamforming algorithm toward a certain direction. In this paper, we study the anti-spoofing techniques using array antenna to overcome the jamming and spoofing issues simultaneously. First, we will present the theoretical analysis results of spoofing signal response of Minimum Variance Distortionless Response (MVDR) algorithm in array antenna. Then the eigenvector algorithm of covariance matrix is suggested and verified to work with the existing anti-jamming method. The modeling and simulation are used to verify the effectiveness of the anti-spoofing algorithm. Also, the field test results show that the array antenna system with the proposed algorithms can perform the anti-spoofing function. This anti-spoofing method using array antenna is very effective in the view point of solving both the jamming and spoofing problems using the same array antenna hardware.

• 한국항행학회논문지
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• 제21권4호
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• pp.339-346
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• 2017

본 논문에서는 위성항법장치와 관성항법장치가 장착된 항체의 고속 이동을 모의하는 환경에서 재밍신호가 인가되었을 때, INS-aided 알고리즘이 장착된 위성항법장치의 재밍대응 성능향상을 검증하기 위한 관성항법장치 모의 장치의 설계 방안을 제시한다. 위성항법 시뮬레이터와 연동하여 관성데이터를 제공할 수 있는 고가의 관성항법장치 시뮬레이터를 대체하기 위해 상대적으로 낮은 가격으로 제작할 수 있는 관성항법장치 모의 장치 설계 방안을 제시하였다. 제안한 설계를 기반하여 제작한 모의 장치를 이용하여 INS-aided 알고리즘이 장착된 위성항법장치의 재밍대응 성능을 검증하기 위해 항체의 고속 이동 환경을 모의한 시험 환경을 구축하였다. 모의 시험을 통해 GPS L1 C/A와 L2C 항법신호에 인가되는 협대역/광대역의 재밍신호에 대응하여 INS-aided 알고리즘 미적용 시와 대비하여 기존 문헌에서 분석한 +5 dB의 재밍대응 성능 향상이 가능함을 확인하였다. 모의 시험 결과를 통해 본 논문에서 설계하여 제작한 관성항법장치 모의 장치가 재밍대응 성능향상 검증을 위한 관성데이터 주입이 가능함을 검증할 수 있었다.

• Journal of Positioning, Navigation, and Timing
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• 제7권3호
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• pp.113-125
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• 2018

Since the global positioning system receivers on the surface of the Earth use satellite signals sent from a remote distance and the intensity of received signals is weak, they are vulnerable to jamming. This paper implements a vector-tracking loop (VTL)-based global navigation satellite system (GNSS) receiver algorithm as an anti-jamming technique and compares the performance of VTL-based receivers with that of scalar-tracking loop (STL) that is used in general GNSS receivers at various jamming environments and a vehicle's dynamics. The simulation results shows that VTL is more robust against jamming than STL in all operating environments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1222-1227
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• 2005

In this paper, an efficient scheme of the adaptive notch filter is presented for rejecting the narrow bandwidth interferences(NBI) in GPS receiver. Designed is the lattice IIR double notch filter for more efficient suppression of the NBI with less computational complexity. The algorithm is of recursive prediction error form and uses a special constrained model of IIR with a minimal number of parameters. This paper chooses seven different jamming scenarios including one without jamming for evaluating the proposed filter algorithm. The simulation results to the jamming scenarios show that the proposed algorithm adjusts the double notch filter effectively for the given JSR, and provides better SNR than the conventional algorithms. Finally, it is shown that the advantages of the proposed filter algorithm can range as high as JSR 79dB in time domain processing. Also, the ADNF(adaptive double notch filter) guarantees that more than SNR 10dB of GPS receiver can be always maintained. In conclusion, there is enough evidence to believe that the proposed algorithm will perform quite well for removing interference signals.

• 한국통신학회논문지
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• 제38C권12호
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• pp.1216-1227
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• 2013

위성항법시스템은 현재 민간과 군에게 위치와 시간 정보를 제공하는 유용한 시스템으로 널리 활용되고 있으며, 국방-IT 간 대표적 융합 기술로 거론되고 있다. 그러나 위성항법시스템은 지구로부터 2만 Km 상공의 원거리에서 신호를 송신하므로 위성항법 수신기의 수신 감도가 매우 미약하여, 재밍(jamming) 공격에 취약한 특성을 가진다. 이와 같은 위성항법시스템을 위한 항재밍(anti-jamming) 기술에 관한 연구는 위성항법시스템을 소유한 국가가 공개하는 기술적 정보에 의존적이어서 국내 국방 분야에서는 소극적 수준의 연구에 머물러 있다. 본 논문에서는 먼저 위성항법시스템의 다양한 재밍원 소개와 J/S와 재머-수신기 간의 거리 링크 버짓 분석을 통한 위성항법시스템의 재밍 취약성을 분석하였다. 또한 위성항법시스템 수신기 설계에 적용 가능한 항재밍 기술을 분류하고 분석하였으며, 최근 연구되고 있는 국내외 항재밍 관련 제품 및 기술을 분석하였다.