• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.851-856
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• 2013

Recently, as the tactical environment has changedto one of network-centric warfare, where all components are connected through a network, much emphasis has been placed on the use of an artificial satellite for achieving high communication speeds. To provide a high-quality artificial satellite link, stabilization is very important in a platform. Previous stabilization control techniques used PI control, which is commonly used for vessels. However, for ground terminals that require a higher communication speed, the antenna should move faster to track an artificial satellite within a short period of time. Moreover, the terminals must be equipped with proper sensors and algorithms so that they can detect and compensate for external disturbances while tracking the artificial satellite. In this study, through the analysis of the dynamic model of an antenna system, a stabilization algorithm for ground terminals was proposed;this algorithm shows high isolation performance in the low-frequency range and includes $PI^2$ control.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.3
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• pp.140-149
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• 2002

This paper describes the characteristics of beam-tilting slot away waveguide antennas for mobile DBS reception. As a basic study of slotted waveguide array, design for 16 slot elements located on a broad-wall waveguide is considered. Design parameters such as slot length, space between each slot and cross slot angle of antennas with the beam-tilting characteristics are calculated by method of moments. Based on these results, the radiation waveguide antennas with 16-element $\times$16-array are designed and fabricated. The measured main beam direction angles of the fabricated antennas are 48$^{\circ}$to 50$^{\circ}$depending on the measured frequencies and it shows good agreement with prediction. The measured 3 dB beam width of elevation pattern is about 13$^{\circ}$, and the axial ratio and the gain measured at DBS band are observed 2.8 dB below and 24 dBi above, respectively. In order to evaluate a performance of the fabricated waveguide planar antenna, it is combined with the satellite tracking control system and the field performance test of antenna mounted on a mobile vehicle is carried out at highway. During the measurement, it was possible to watch television without a break signal in a driving vehicle and an excellent performance of the proposed antennas was demonstrated.

• Journal of Internet Computing and Services
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• v.9 no.1
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• pp.43-54
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• 2008

In this paper, we implement an automatic entity information management system for smart refrigerator using RFID technology in which objects containing electronic tags are automatically identified using radio wave. Unlike current "smart" refrigerators, the system presented in this paper implements smart tag information acquisition mechanism and real-time information management system to provide various information on entities in refrigerators to local and remote users. As the first step, this paper analyzes the requirements for smart refrigerator system based on the RFID and suggests design considerations. Based on the analysis, we propose and implement an efficient tag location tracking method based on antenna transfer method and an intelligent tag information management system based on embedded database and web server. We also provide a wide range of experimental results on the number of tags identified at a time and the tag recognition ratio according to the RFID antenna transfer speed and the angle between tag reader and tags.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.3
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• pp.43-49
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• 2008

The Real Time Location System (RTLS) is very important in the ubiquitous society for real time tracking of men, high price assets, and logistics products. In this work, we developed an active RF system for RTLS and tested its performance. The RTLS system developed in this work was constructed of three active readers and one active tag. The small size tag developed in this work operated with a coin type battery. To make the tag smaller, we used an internal PCB antenna and a chip antenna. We tested the performance of the tag. To reduce the manufacturing cost of our RF system, we used low price RF transceiver CC2510 chip-set. The CC2510 chip-set provided RSSI(Received Signal Strength Indicator) signal which could be used to determine the distances between an active tag and three active readers.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.89-100
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• 2016

Given the unpredictability of the space environment, satellite communications are manually performed by exchanging telecommands and telemetry. Ground support for orbiting satellites is given only during limited periods of ground antenna visibility, which can result in conflicts when multiple satellites are present. This problem can be regarded as a scheduling problem of allocating antenna support (task) to limited visibility (resource). To mitigate unforeseen errors and costs associated with manual scheduling and mission planning, we propose a novel method based on a genetic algorithm to solve the ground support problem of multiple satellites and antennae with visibility conflicts. Numerous scheduling parameters, including user priority, emergency, profit, contact interval, support time, remaining resource, are considered to provide maximum benefit to users and real applications. The modeling and formulae are developed in accordance with the characteristics of satellite communication. To validate the proposed algorithm, 20 satellites and 3 ground antennae in the Korean peninsula are assumed and modeled using the satellite tool kit (STK). The proposed algorithm is applied to two operation modes: (i) telemetry, tracking, and command and (ii) payload. The results of the present study show near-optimal scheduling in both operation modes and demonstrate the applicability of the proposed algorithm to actual mission control systems.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.2
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• pp.117-124
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• 2022

Single-ring circular array antennas can be applied to direction finding systems in order to use nose-section in other purposes, and the interferometry is a proper direction finding method to those systems. We usually make the interferometer baseline long enough to achieve good angular accuracy. However, an interferometer with baseline longer than a half-wavelength has the ambiguity problem. In this paper, we present a novel method for solving the ambiguity problem in interferometry systems. This technique is based on the amplitude comparison method and the space division table, and it can place a target within the angular region in which the ambiguity problem does not occur by roughly estimating direction-of-arrival. The Monte Carlo simulation results show that proposed method can effectively remove the ambiguity problem in the system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.362-370
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• 2011

This paper presents a K-band radar system installed on the ground moving vehicle to detect and track a high-speed target. The presented radar is separated into three search regions to satisfy a wide area detection and a limitation of the installing space of the radar, and each region performs detecting the target independently and tracking the detected target automatically. The presented radar radiating K-band FMCW waveform acquires range and velocity information of the target at the every dwell and receiving antenna of the radar is applied the multiple baseline interferometer to extract the precise angle information of the target. 3-dimensional tracking accuracy of the radar is 0.25 m RMSE measured actually through a fire experiment of an imitation target.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.275-282
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• 2015

Recently, telemetry systems are used to test and evaluate of ammunition. When a transmitting signal from a small transmitter mounted inside the ammunition is sent out, the receiving equipments get real-time RF data. This paper relates to the development of a small high-G endurable transmitter and a portable receiving equipment. The system was tested and confirmed 00 km communication range.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.890-893
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• 2014

In this paper, we present a signal processing algorithm for a marine radar system, in which the evaluation of probability of collision as well as target detection and tracking are performed. Moreover, the digital signal processor that implements the algorithm is proposed. As simulation environment, a mechanically scanning antenna utilizing FMCW signal is used, conducting the beamforming operation with 1 degrees intervals. Test board consists of DSP chips and FPGA, which enable the implemented system to operate in real-time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.5
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• pp.1471-1483
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• 2023

One of the fastest-growing mobile services accessible today is mobile payments. For the safety of this service, the Near Field Communication (NFC) technology is used. However, NFC standard protocol has prioritized transmission rate over authentication feature due to the proximity of communicated devices. Unfortunately, an adversary can exploit this vulnerability with an antenna that can eavesdrop or alter the exchanged messages between NFC-enabled devices. Many researchers have proposed authentication methods for NFC connections to mitigate this challenge. However, the security and privacy of payment transactions remain insufficient. We offer a privacy-preserving, anonymity-based, safe, and efficient authentication protocol to protect users from tracking and replay attacks to guarantee secure transactions. To improve transaction security and, more importantly, to make our protocol lightweight while ensuring privacy, the proposed protocol employs a secure offline session key generation mechanism. Formal security verification is performed to assess the proposed protocol's security strength. When comparing the performance of current protocols, the suggested protocol outperforms the others.