• The Journal of the Acoustical Society of Korea
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• v.17 no.6
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• pp.29-36
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• 1998

본 논문은 확산된 데이터에 반송파를 1개가 아닌 여러 개의 반송파로 변조하는 MC DS-CDMA 시스템을 적용하여 페이딩 요소를 고려하지 않는 채널, 즉 Gaussian 채널에서 다중 사용자 간섭 및 부분대역 재머, 최악의 부분대역 재머 간섭하에서 성능을 분석하여 단 일 반송파를 사용한 기존의 DS-CDMA 시스템과 비교 분석한다. 또한, Gaussian채널에서 고려된 간섭들에 대해 다중경로 페이딩 채널에서 시스템 성능을 분석하고 Gaussian채널에 서 분석된 시스템 성능과 비교한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.6
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• pp.729-737
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• 2012

In case that multiple jammers are transmitting the signals which are the same type a general algorithm based on TDOA method cannot estimate the positions of multiple jammers because there are many TDOA measurements including true and false values. This paper, therefore, designs a new algorithm based on TDOA method to localize multiple jammers. In this algorithm, TDOA measurements are obtained by rotating the reference sensor, and then the positions of multiple jammers can be estimated by detecting congregated point among the multiple estimated positions from TDOA measurements. Through computer simulations, it is verified that this algorithm localizes the multiple jammers well. The performance of the algorithm are also analysed by changing the distance between sensors and jammer, and sampling frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.492-499
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• 2002

Performance analysis and comparison of the hybrid DS-SFH spread-spectrum (SS) system using coherent MSK and QPSK modulation techniques over Rayleigh fading channel are considered in the presence of MTJ(multi-tone jamming). To analyze the BER performance of the hybrid systems with or without the Rake receiver, signal-to-noise plus interference ratio is derived as a function of the average signal-to-noise ratio, the jammer-to-signal ratio and other system parameters. Numerical results show that the performance difference between the two modulation schemes, MSK and QPSK, is negligible for low JSR, while it becomes significant with the increase of JSR. In multi-path Rayleigh fading channel without Rake receiver, the performances of the two modulation schemes are slightly improved as the DS spreading gain is increased when the total SS bandwidth is fixed. In particular, there is an optimum DS spreading gain for large JSR, in which a minimum BER is achieved, while only DS spreading gives the best performance for small JSR. For hybrid systems with Rake receiver, it is shown that the hybrid system of the MSK modulation scheme provides better anti-jamming performance and larger performance improvement with the increase of multi-path resolution capability of Rake receiver than that of QPSK modulation for all conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.491-498
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• 2017

GPS (global positioning system) is a popular system that provides location information by measuring arrival time difference at the receiver between several GPS satellite signals. GPS is widely used in commercial area as well as military systems. Reliable GPS signal reception is more important in the military applications such as guided missiles. However, since the carrier frequencies of the GPS signals are well known and the received power is extremely low, the GPS systems are vulnerable to intentional jamming attacks. To remove jammers while maintaining GPS signals at the received signals, a popular technique is an adaptive beam steering method based on array antenna. Among adaptive beam steering techniques, this paper considers MVDR (minimum variance distortionless response) algorithm, and proposes a new adaptive technique that preserves the received signals at desired directions, but removes the unknown jamming signals adaptively. The performance of the proposed method is verified through computer simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.137-144
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• 2009

This paper deals with the performance comparison of jammer signal's angle spreading in the beamforming after the estimation of direction of arrival using 3D array antenna basis of the GPS signal. After the estimation of direction of arrival using array antenna, the beamforming is need for the direction of arrival by spatial filtering and the other direction are nulling for reducing intererence signal, it is possible to improving the received signal strength and quality. But we obtains the degraded performance by the angle spreading due to the multi-jammer signal in this process. In this paper, the MUSIC and LCMV algorithms are applied for the estimating the direction of arrival and for beamforming using the 5 types of 3D array antenna. we performs the comparison of performance by calculating the bit error rate applying the BPSK modem and the varying the azimuth and elevation angle of incoming jammer signal. As a result of simulation, the Curved (B) type 3D array antenna has a more better performance compared to the other type antenna.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1539-1545
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• 2015

GPS (global positioning system) is a popular system that provides location information by measuring arrival time difference at the receiver between several GPS satellite signals. GPS is widely used in commercial area as well as military systems. Reliable GPS signal reception is more important in the military systems. However, since the carrier frequencies of the GPS signals are well known, the GPS receivers are vulnerable to intentional jamming attacks. To remove jammers but maintain GPS signals at the received signals, a popular technique is an adaptive beam steering method based on array antenna. Among adaptive beam steering techniques, this paper considers MVDR (minimum variance distortionless response) algorithm, and proposes a new adaptive technique that preserves the received signals at desired direction, but removes the jamming signals adaptively. The performance of the proposed method is verified through computer simulation.

• Journal of Advanced Navigation Technology
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• v.17 no.4
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• pp.386-395
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• 2013

This paper proposes a root-assisted MUSIC algorithm which uses a combination of the MUSIC and the root-MUSIC algorithm. This algorithm consists of two steps. Firstly, a coarse DOA is computed by the root-MUSIC algorithm. Secondly, a precise DOA estimation is carried out by the MUSIC algorithm in the reduced searching range. This paper analyzes the accuracy and the resolution performance of the proposed DOA estimation method using a software simulation platform.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1410-1413
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• 2016

Array beamforming for anti-jamming means that jamming signals are superposed destructively, while superposing information signals constructively at a receiver. However, according to channel state variation, the anti-jamming performance of the beamforming can be degraded because of large beamwidth of the sidelobe and lower selectivity of the mainlobe. To mitigate this problem, we introduce a beamformed decoy signal which uses frequency band distinguished from the information signal to make the jammer concentrate its jamming power to a wrong target under limited feedback. In this paper, we show that the performance of the proposed scheme can approach that of optimal one with perfect feedback.

• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.9-13
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• 2022

In this paper, the tracking error of monopulse radar caused by cross-eye jamming using terrain bounce is analyzed. Cross-eye jamming is a method of generating an error in a radar tracking system by simultaneously transmitting two signals with different phases and amplitudes. When the monopulse radar receives the cross-eye jamming signal generated by the terrain bounce, a tracking error occurs in the elevation direction. In the presence of multipath, this signal is a combination of the direct target return and a return seemingly emanating from the target image beneath the terrain surface. Terrain bounce jamming has the advantage of using a single jammer, but the space affecting the jamming is limited by the terrain reflection angle and the degree of scattering of the terrain. This study can be usefully used to protect ships from low-altitude missiles or aircraft in the sea.