• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.5
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• pp.366-374
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• 2018

In cases of airborne equipped with SAR, because the occurrence of motion is inevitable, it is necessary to apply autofocus techniques to SAR images to improve the image performance degradations caused by residual errors. Herein, a robust autofocus algorithm based on the minimum entropy criteria is proposed for the real SAR data in the spotlight mode. The convergence condition of the phase error estimation is checked at every iteration and if it is violated, the size of the phase error estimation is adjusted to the convergence condition. The real SAR raw data is used to demonstrate the excellent performance of the proposed algorithm.

• Journal of the Korean Society of Safety
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• v.30 no.2
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• pp.63-69
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• 2015

Recoilless weapons, which lead strong back blast and impulse noise more than 160 dB, have been used in compliance with the regulation of the safety zone for the safe operations. However, the safety zone regulations for the newly developed weapons should be prepared since the existing guidelines do not provide any information concerning the reason for the safety zone. In this study, the outdoor launch tests were performed to collect the data such as noise, pressure and temperature of the back blast. An assessment method using data obtained from launch tests has been proposed to determine the safety zone. The safety zone has been determined with consideration for the following criteria: Impulse noise, temperature and pressure of the back blast and blast angle. As a results, new safety zones for them have been established for the recoilless weapon developed by ADD (Agency for Defense Development). We expect that this research can be used as a guideline for establishing a new safety zone regulation of similar weapon to be developed.

• Journal of Ocean Engineering and Technology
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• v.34 no.4
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• pp.277-284
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• 2020

Underwater acoustics, which is the study of phenomena related to sound waves in water, has been applied mainly in research on the use of sound navigation and range (SONAR) systems for communication, target detection, investigation of marine resources and environments, and noise measurement and analysis. The main objective of underwater acoustic remote sensing is to obtain information on a target object indirectly by using acoustic data. Presently, various types of machine learning techniques are being widely used to extract information from acoustic data. The machine learning techniques typically used in underwater acoustics and their applications in passive SONAR systems were reviewed in the first two parts of this work (Yang et al., 2020a; Yang et al., 2020b). As a follow-up, this paper reviews machine learning applications in SONAR signal processing with a focus on active target detection and classification.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.1
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• pp.1-9
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• 2018

In this paper, we have proposed a prediction method for sabot-trajectory of projectile using high speed camera data analysis. Through analyzing trajectory of sabot with high speed camera data, we can extract its real velocity and acceleration including effects of friction force, pressure of flume, etc. Using these data, we suggest a prediction method for sabot-trajectory of projectile having variable acceleration, especially for minimum and maximum acceleration, by using interpolation method for velocity and acceleration data of sabot. Also we perform the projectile launching tests to achieve the trajectory of sabot in case of minimum and maximum thrust. Simulation results show that they are similar to real tests data, for example velocity, acceleration and the trajectory of sabot.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.5
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• pp.607-617
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• 2014

This paper proposed the M&S(Modeling & Simulation) method of channel characterization of satellite communication in the operating area of satellite OTM(On-The-Move) terminal. In M&S, received signal profile was acquired by HTZ warfare software which uses 3 dimensional map including building, road information and geographical features, and then was analyzed statistically. And a received signal profile and its statistics from M&S data were compared with those from measured data. The research showed that the simulated received signal profile matched the measured one about 74.8 percent and simulated statistics matched well as roadside trees were excluded.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.316-323
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• 2016

A UAV(Unmanned Aerial Vehicle) flies along pre-programed navigation points(in-flight, take-off, or landing) automatically without pilot input. Even though UAVs fly differently from general piloted aircraft as the pilot controls the aircraft from a ground station through means of a data-link system. Occasionally, the data-link connection can be lost for any number of reasons, in which case, the FLCC(Flight control Computer) must automatically switch to autopilot to continue flying. Hence, the FLCC is a flight-critical component that must be throughly tested and validated. This paper discusses the development of a HILS(Hardware in the Loop Simulation) test environment designed to simulate real flight conditions to verify the FLCC satisfies flying quality requirements and maintains robustness despite any potential malfunctions or emergency situations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.2
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• pp.83-92
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• 2022

This paper analyzes the performance of the IRA(Interferometric Radar Altimeter) by terrain type for estimating reliability of TRN(Terrain Referenced Navigation). The accuracy of the altitude is one of the key parameters of TRN's accuracy. When the antenna of the IRA has wide beamwidth, its altitude accuracy is directly affected by the configuration of the earth's surface. Hence, the accuracy and reliability of TRN can also be affected and may cause ambiguity in positioning. We present analysis data for estimating the reliability of TRN by modeling several topographies and analyzing the performance of the IRA. The results of the analysis are verified by comparison with test data.

• Journal of the Korea Society of Computer and Information
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• v.29 no.10
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• pp.59-68
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• 2024

In this study, we proposed an efficient model that can detect and classify the drones and related devices based on radio frequency signals. In order to increase the applicability in the battlefield, proposed model was designed to be lightweight, to ensure rapid detection and high detection accuracy. Data preprocessing was performed by applying a Discrete Fourier Transform (DFT) that is faster than Hilbert-Huang Transform (HHT). We adopted the LightGBM model as the learning model, which can be easily used by non-professionals and guarantees excellent performance in terms of classification speed and accuracy. CardRF dataset was used to verify the performance of the proposed model. As a result of the experiment, the accuracy of 3 classes classification for detecting and classifying drones, WiFi, and Bluetooth device was 99.63% when the number of sample points was set to 100k and 99.40% when set to 500k during the data preprocessing with DFT. And, in the 10 classes classification for 6 drones, 2 Bluetooth devices, and 2 WiFi devices, the accuracy was 95.65% for 100k and 96.83% for 500k, confirming significantly improved detection performance compared to previous studies.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.3
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• pp.158-164
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• 2002

2-6 GHz digital phase shifter module has been designed and fabricated. For the broadband operation and performance, MMIC phase shifter chip for phase shifter module was designed and fabricated by using the reflection-type circuits with Lange coupler. The fabricated phase shifter module shows 6.1$^{\circ}$RMS phase error, 13.5 dB maximum insertion loss, and 8 dB and 10 dB input and output return losses, respectively. Computer controlled measurement systems are realized in order to get the measured data of 32 phase states. The RMS insertion phase error and the average insertion loss deviation among 8${\times}$8 modules for the phased-array system are less than ${\pm}$0.5$^{\circ}$and ${\pm}$0.5 dB, respectively. The size of fabricated phase shifter module is 45 ${\times}$ 22.5 ${\times}$60㎣.

• Journal of Korean Society for Quality Management
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• v.45 no.3
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• pp.335-347
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• 2017

Purpose: Defense government agencies in the world continuously try to improve operational efficiency in government quality assurance activities. The purpose of this paper is to propose some suggestions to enhance efficiency of government quality assurance (GQA) activities based on the analysis of the current quality assurance methods of advanced foreign agencies such as DCMA and NATO. Methods: In order to propose new directions, reviews and analyses are executed. (1) Former research results in Korea for enhancing GQA are reviewed, and their limitations are addressed. (2) Updated policies and procedures of the US DCMA and NATO are reviewed and their advantages are presented. (3) Current GQA policies and procedures are contrasted with those of US DCMA and NATO. Results: Suggestions for efficient Korean GQA activities are given in several aspects: GQA paradigm shift, clarification of GQA methods, facility-wide GQA, risk management for suppliers, counterfeit mitigation policy, data collection and control. Conclusion: Reviews on the government quality assurance policies and procedures of DTaQ, DCMA, and NATO are executed and compared with each other. The results of this research are expected to be useful guidelines to improve GQA policies and procedures in Korea, making it possible to realize more efficient GQA activities in Korea.