• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.22-28
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• 2017

In modern electronic warfare, a variety of devices are being operated in the fields for the purposes of communication and surveillance. Therefore, if such devices work in the same band, interference may occur and affect each other. Regarding L-band in which various devices including radar systems are operating, interference from existing devices may affect new ones in the band. In this paper, we estimate a probability distribution of the interference environment in L-band from the selected measurement data, which is fundamental for the mathematical analysis. After selecting the candidates of probability distribution, we suggest the best one from the group. The results of this study are expected to be utilized as fundamental data for the mathematical approach to the L-band interference environment.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.3
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• pp.290-294
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• 2018

Modern warfare exhibit a NCW (Network Centric Warfare) aspect through quick situation awareness and Command and Control. And Tactical messages operate on various tactical data links (TDLs). For monitoring TDL messages processed by data link processor(DLP), message analysers are generally developed as a component during system development. In addition, in order to forward TDL messages processed by DLP to the message anayzer, the interface messages between DLP and message analysers should be defined interface control document(ICD). We propose the methods using UDP or TCP packets provided by TDL layers that are delivered to DLP without communicating directly with DLP. Depending on TDL message standards and Interface Control Documents(ICDs), we design the message analyzer which communicates with data link processor using internal messages. Using known header field information from the TDL application standard such as JREAP-C, we can quickly filter candidate packets against collected packets and use the full data size information contained in the headers to verify the completed message. Because the methods proposed in this paper do not communicate directly with DLP, the methods proposed in this paper are enable to analyze the TDL application messages such as JREAP-C or Link-K without constraints in existing methods that should be reflected in the system configuration and ICD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.392-401
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• 2012

This paper gives a electromagnetic coupling mechanism of the high altitude electromagnetic pulse (HEMP) into large- scale underground multilayer structures using analytic and numerical methods. The modeling methods are firstly addressed to the HEMP source which can be generated by intentional nuclear explosion. The instantaneous and intense electromagnetic pulse of the HEMP source is concerned from DC to 100 MHz band, because the power spectrum of the HEMP is rapidly decreased under -30 dB over the 100 MHz band. Through this range, a penetrated electric field distribution is computed within the large-scale underground multilayer structures. As a result, the penetrated electric field intensities at 0.1 and 1 MHz are about 10 and 5 kV/m, respectively. Therefore, additional shielding techniques are introduced to protect buried structures within the large-scale underground structures such as high-lossy material and filtering structures (wire screen).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.151-158
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• 2012

This paper proposes a H-plane 8-way rectangular waveguide power divider using Y-junction. A general N-way power divider can be composed of multi-stage T-junctions. However, if the distances of output ports are close, the matching characteristic is not improved by using only T-junctions because of space limitation. In this case, since other types of 3-port junctions should be used to final output stage, Y-junctions are used with T-junctions in this paper. The proposed Y-junction uses the tapered-line impedance transformer and inductive irises to improve impedance matching characteristic. The 8-way power divider using Y-junction is fabricated and measured. The measured return loss and insertion loss from input port to output port are -30.8 dB and -9.3 dB at operating frequency, respectively. The measured maximum phase difference is about $1^{\circ}$. Therefore, the proposed power divider will be useful to apply to various microwave systems, which need to divide the input power equally, such as feed networks for array antennas.

• Journal of Internet Computing and Services
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• v.21 no.6
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• pp.1-12
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• 2020

Low-Orbit satellite mobile networks can provide services through miniaturized terminals with low transmission power, which can be used as reliable means of communication in the national public disaster network and defense sector. However, the high traffic environment in the emergency preparedness situation increases the new call blocking probability and the handover failure probability of the satellite network, and the increase of the handover failure probability affects the QoS because low orbit satellites move in orbit at a very high speed. Among the channel allocation methods of satellite communication, the FCA shows relatively better performance in a high traffic environment than DCA and is suitable for emergency preparedness situations, but in order to optimize QoS when traffic increases, the new call blocking and the handover failure must be minimized. In this paper, we propose LEO-DBC (LEO satellite dynamic beam width control) technique, which improves QoS by adaptive adjustment of beam width of low-orbit satellites and call time of terminals by improving FCA-QH method. Through the LEO-DBC technique, it is expected that the QoS of the mobile satellite communication network can be optimally maintained in high traffic environments in emergency preparedness situations.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.2
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• pp.152-163
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• 2022

In this paper, we present a method to enable an unmanned aerial vehicle to drop the sonobuoy, an essential element of anti-submarine warfare, in an optimal deployment. To this end, an environment simulating the distribution of sound detection performance was configured through the Unity game engine, and the environment directly configured using Unity ML-Agents and the reinforcement learning algorithm written in Python from the outside communicated with each other and learned. In particular, reinforcement learning is introduced to prevent the accumulation of wrong actions and affect learning, and to secure the maximum detection area for the sonobuoy while the vehicle flies to the target point in the shortest time. The optimal placement of the sonobuoy was achieved by applying the Deep Deterministic Policy Gradient (DDPG) algorithm. As a result of the learning, the agent flew through the sea area and passed only the points to achieve the optimal placement among the 70 target candidates. This means that an autonomous aerial vehicle that deploys a sonobuoy in the shortest time and maximum detection area, which is the requirement for optimal placement, has been implemented.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.6
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• pp.669-675
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• 2014

In this paper, we described the investigated theoretical time synchronization performances and experiment results obtained by commercially provided PTP (Precise Time Protocol) modules when the time of a slave clock is synchronized to the master clock. In the case of the theoretical performance analysis, we investigated 3 types of clock levels such as Crystal Oscillator (XO), TCXO (Temperature Compensated XO) and OCXO (Oven Controlled XO). From the analysis, it was observed that the synchronization performance is greatly influenced by the synchronization period and the required performance under 1 us can be achieved by using XO level clocks when the synchronization period is less than 2 seconds and the uncertainty of the propagation delay is under 100 ns. For the experiments using commercial PTP modules, the synchronization performance was investigated for direct, through 1 hub and through 2 hubs connections between the master clock and the slave clock. From the experiment results, we observed that time synchronization under 90 ns with 1,000 seconds observation interval can be achieved in the case of direct connection.

• Journal of Internet Computing and Services
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• v.10 no.3
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• pp.35-49
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• 2009

In electronic warfare settings, battlefield helicopters identify various threats based upon threat data, which are acquired using their multi-sensors of aircraft survivability equipment (ASE). To continually function despite of potential threats and successfully execute their missions, the battlefield helicopters have to repeatedly report threats in simulated battlefield situations. Toward this ends, the paper presents threat unification using multi-sensor simulator and its implementation. The simulator consists of (1) threat attributes generator, which models threats against battlefield helicopters and defines their specific attributes, (2) threat data generator, which generates threats, being similar to real ones, using normal, uniform, and exponential distributions, and (3) graphic display for threat analysis and unification, which shows unified threat information, for example, threat angle and its level. We implement a multi-sensor threat simulator that can be repeatedly operable in various simulated battlefield settings. Further, we report experimental results that, in addition to tangibly modeling the threats to battlefield helicopters, test the capabilities of threat unification using our simulator.

• Journal of the military operations research society of Korea
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• v.17 no.2
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• pp.1-15
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• 1991

If one were to say that war is political in its nature, then war could be one of the several ways of achieving political goals. Thus, the aspect of wars will, in certainty, be altered by the changes in political environment. Wars in the past broke out mainly due to ideological differences that ran to extremes and were of high intensity. However, wars today show such restraints as controlling them beforehand or during the war in anticipation of the post-war situation. The trend of ideas to actualize such wars in the effective operation of airpower is on the rise. Airpower normally possesses speed and operative flexibility as well as capability of destruction, so it is possible to destroy the politically declared targets clearly. Previous airpower was merely employed as means of helping to vertically detouring the spatial obstacle that the ground forces encountered. Over the years, due to the speedy improvement of aviation technology and of ideas concerning wars in space, more advanced application has been developed. but they also were nothing more than an auxiliary role to facilotate the ground forces, that needed a longer effective range of firepower and did not become forces with the right of self-determination, that is, the fact of decisive war that makes its outcome. However, under transitional strategic environment like that of the present, Airpower possesses not only the capability to operate as a decisive means of war but also as theories to support it. The advancement in air technology has enabled supremacy over targets in depth, and the development of electronic technology has empowered the improvement of degree of destruction but also triumphant war by means of an overwhelming supremacy in a relatively short period. Thus, the method of systematic destruction that accomplishes the stated goals while rejecting the damage of accumulative destruction has been realized. The progress of such a concept has also proved that the counter-force strategy that has been developed in nuclear strategy is useful in conventional warfare as well. Therefore, it can be said that the under today's strategic environment airpower is an outstanding means of military strategy that can deeply affect to achieve the national objectives.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.5
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• pp.602-611
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• 2015

Even though GNSS provides highly accurate navigation information all over the world, it is vulnerable to jamming in the electronic warfare due to its weak signal power. The United States and Korea have plans to use terrestrial navigation systems as back-up systems during outage of GNSS. In order to develop back-up systems of GNSS, an M&S software platform is necessary for performance evaluation of various vehicle trajectories and integrated navigation systems. In this paper a design method of an M&S software is proposed for evaluation of multiple radio positioning integration systems. The proposed M&S software consists of a navigation environment generation part, a navigation algorithm part, a GUI part and a coverage analysis part. Effectiveness of the proposed design method is shown by implementing an M&S software for the GPS, DME and eLoran navigation systems.