• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.69-73
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• 2011

In the defence wireless communications, conventional Anti-Jamming techniques(Frequency Hopping/Spread Spectrum or Direct Sequence/Spread Spectrum) are used to overcome a intentional interfering signals which are single/multitone or partial band jammer etc. DS/SS techniques is very strong on tone jamming signal but not to be on a partial band jammer. So FH/SS AJ performances are expected method of an substitution of DS/SS, however FH/SS could not have good performance on some BMTJ(Band Multi-tone Jammer). So this paper proposes FH-CSS (Frequency Hopped - Chirp Spread Spectrum) to get more robustness against jammers(BMTJ, PBNJ) and analyze the AJ performances.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.71-75
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• 2018

In this paper, we study the secrecy outage probability when using jammer in a relay system based on decode-and-forward. The jammer may be selected among the relays not selected to increase the security capacity in the physical layer so as to generate intentional noise. Jammer noise can equally interfere with the receiver and eavesdropper but can enhance the physical layer security by selecting an optimal jammer that makes the channel quality between the sender-eavesdropper links worse than the channel of the sender-receiver link. In this paper, we compute the theoretical formula of the secrecy outage probability with and without jammers, and compare the theoretical value with the simulation value to prove that the equation is valid.

• Journal of Convergence for Information Technology
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• v.10 no.6
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• pp.14-18
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• 2020

In this paper, when two sets of cross-eye jammer antennas are installed vertically to jam a monopulse radar, the jamming effects according to the jammer's phase difference, amplitude ratio, and radar angle of engagement are analyzed. The phase difference and amplitude ratio of the cross-eye jammer can be adjusted in the jammer, but since the angle of engagement is relatively determined by the radar, it is very important to respond to changes in the angle of engagement. The orthogonally deployed jammer antennas can be considered as a good way to increase the jamming effect while minimizing the hardware configuration, and the jamming effect is analyzed while changing the angle of inclination from 0° to 360°. This jammer greatly improves the jamming effects at the angles of incidence 45°~135° and 225°~315°, compared to a single jammer. And it is expected to be useful in the design of cross-eye jammers for military aircraft and ships.

• International Journal of Control, Automation, and Systems
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• v.5 no.2
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• pp.200-207
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• 2007

The passive direction finding cross localization method is widely adopted in passive tracking, therefore there will exist masses of false intersection points. Eliminating these false intersection points correctly and quickly is a key technique in passive localization. A new method is proposed for passive locating and tracking multi-jammer target in this paper. It not only solves the difficulty of determining the number of targets when masses of false intersection points existing, but also solves the initialization problem of elastic network. Thus this method solves the problem of multi-jammer target correlation and the elimination of static false intersection points. The method which dynamically establishes multiple hypothesis trajectory trees solves the problem of eliminating the remaining false intersection points. Simulation results show that computational burden of the method is lower, the elastic network can more quickly find all or most of the targets and have a more probability of locking the real targets. This method can eliminate more false intersection points.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.49-54
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• 2018

In this paper, we study the secrecy outage probability when using cooperative diversity and jammer in a relay system based on decode-and-forward. MRC method is used in receiver and eavesdroppers to obtain cooperative diversity. To use the MRC technique, direct links between the sender and receiver, and between the sender and the eavesdropper are used, respectively. Jammers are used to generate intentional noise siganls to increase security capacity. Jammers generate intentional noise, degrading the channel quality of the eavesdropper and helping physical layer security be realized. The secrecy outage probability is used to evaluate security performance. Assume that the system is under the Rayleigh fading channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.2
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• pp.226-237
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• 1998

In recent SATCOM systems, transparent transponders are widely used. The transponder is, however, the most vulnerable part in SATCOM systems against jamming interference. All signals within the transponder bandwidth are frequency-converted and retransmitted with IM(intermodulation) products. In this paper, the method is proposed that makes the SJR(Signal-to-Jammer ratio) better. The bandwidth spreading of the user signal can reduce the jammers effects. The geostationary satellite system is modeled to simulate and to certificate the capability of suppression of jammers by DSSS. If signal is partially-overlapped by jammer and PG(processing gain) is 16.9 [dB] for 2ASK jammer and about 16.8 [dB] for QPSK jammer, when BER is $10^{-3}$.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.9
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• pp.3444-3457
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• 2021

In the field of anti-jamming based on dynamic spectrum, most methods try to improve the ability to avoid jamming and seldom consider whether the jammer would perceive the user's signal. Although these existing methods work in some anti-jamming scenarios, their long-term performance may be depressed when intelligent jammers can learn user's waveform or decision information from user's historical activities. Hence, we proposed a hidden anti-jamming method to address this problem by reducing the jammer's sense probability. In the proposed method, the action correlation between the user and the jammer is used to evaluate the hiding effect of the user's actions. And a deep reinforcement learning framework, including specific action correlation calculation and iteration learning algorithm, is designed to maximize the hiding and communication performance of the user synchronously. The simulation result shows that the algorithm proposed reduces the jammer's sense probability significantly and improves the user's anti-jamming performance slightly compared to the existing algorithms based on jamming avoidance.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.146-153
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• 2008

High-power communication jammer has to include the switched filter bank to eliminate the harmonic signals generated by amplifier. Generally, the switched filter bank consists of in-out switches and several filters. This paper describes the design of high-power switched filter bank, particularly the high-power filter bank operating over 20$\sim$110MHz frequency range. The filters designed have insertion loss less than 0.3dB, VSWR less than 1.25:1, and harmonic suppression more than 35dB. Also, the switched filter bank can endure upto 2kW high-power signal with very low harmonic level within $30{\mu}s$ switching speed.

• ETRI Journal
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• v.43 no.4
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• pp.758-768
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• 2021

In this work, the secrecy of a typical wireless cooperative dual-hop non-orthogonal multiple access (NOMA)-enabled decode-and-forward (DF) relay network is investigated with the impact of collaborative and non-collaborative eavesdropping. The system model consists of a source that broadcasts the multiplexed signal to two NOMA users via a DF relay, and information security against the eavesdropper nodes is provided by a helpful jammer. The performance metric is secrecy rate and ergodic secrecy capacity is approximated analytically. In addition, a differential evolution algorithm-based power allocation scheme is proposed to find the optimal power allocation factors for relay, jammer, and NOMA users by employing different jamming schemes. Furthermore, the secrecy rate analysis is validated at the NOMA users by adopting different jamming schemes such as without jamming (WJ) or conventional relaying, jamming (J), and with control jamming (CJ). Simulation results demonstrate the superiority of CJ over the J and WJ schemes. Finally, the proposed power allocation outperforms the fixed power allocation under all conditions considered in this work.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.676-683
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• 2016

In this paper, an adaptive nulling algorithm which can be used to form nulls in the direction of jammer or interference signals in array antennas of single port system is proposed. The proposed adaptive algorithm does not require a priori knowledge of the incoming signal direction and can be applied to the partially adaptive arrays. This algorithm is the combination of the PSO(Particle Swam Optimization) algorithm and the gradient-based perturbation adaptive algorithm, which shows stable nulling performance adaptively even on the moving jammer environment where the incident direction of the interference signal is changing with time.