• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.91-96
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• 2017

In this paper, we proposed a meander sleeve monopole antenna for low earth orbit satellite communications. The antenna has broadband property with the planar monopole and ground of meander sleeve. Monopole and ground conductors of the antenna are on the same plane, and exited through coaxial cable feeding. In order to confirm the property of antenna parameters, it was used a commercial software, HFSS, For the antenna fabrication, a FR4 dielectric substrate has a dielectric constant of 4.4 was used. The size of the antenna was $600mm{\times}20mm{\times}1.6mm$. Frequency band of the fabricated antenna was 130MHz~151MHz, and the bandwidth was 20MHz. Measurement results of the fabricated antenna, the return loss is more than -10dB return loss in the band could be obtained. Radiation pattern has a maximum gain of 2.64dBi value.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.77-82
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• 2010

The tracking performance of the big tracking antenna system using Radio Frequency is very important for the tracking and position measuring for the flight vehicle, but the precise measuring of the tracking performance is not easy, especially for the big antenna system such as ground telemetry antenna or tracking radar in space application because it's characteristics could be different in accordance with the antenna direction. In this paper, the error factors impacting on the tracking performance (pointing accuracy and tracking accuracy) and the ranges of each factor are reviewed, and the simple and efficient method to measure the tracking performance is introduced which using low earth orbit as the signal source. Finally, the measurement results for the telemetry ground antenna in NARO Space Center are reviewed.

• Journal of the Korea Society of Computer and Information
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• v.29 no.1
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• pp.121-130
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• 2024

In this paper, we propose an installation approach for Naval Combat Management System(CMS) software that identifies potential data anomalies during installation. With the popularization of wireless communication methods, such as Low Earth Orbit(LEO) satellite communications, various utilization methods using wireless networks are being discussed in CMS. One of these methods includes the use of wireless network communications for installation, which is expected to enhance the real-time performance of the CMS. However, wireless networks are relatively more vulnerable to security threats compared to wired networks, necessitating additional security measures. This paper presents a method where files are transmitted to multiple nodes using encryption, and after the installation of the files, a validity check is performed to determine if there has been any tampering or alteration during transmission, ensuring proper installation. The feasibility of applying the proposed method to Naval Combat Systems is demonstrated by evaluating transmission performance, security, and stability, and based on these evaluations, results sufficient for application to CMS have been derived.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.857-864
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• 1998

The infuluence of Doppler effects on the tracking performance of a noncoherent second-order delay locked loop (DLL) operating on a data modulated signal is investigated. For the perfoermance analysis we consider the tracking accuracy (steady state error and jitter) of the linear DLL and the reliability of the nonlinear loop. The nonlinear analysis concerning the loop reliability makes use of an asympototic expansion for the MTLL(mean time to lose lock) which has been derived by applying the singular perturbation method. In particular, we give optimal loop parameters and the optimal bandwidth of the bandpass filter in the loop arms to achieve a maximum MTLL. Since Doppler effects can be producesd comparatively in LEO system, we can espect the more reliable DLL loop design. by using the results of the circuit simulation, the delay lock loop is synthesized in FPGA, and verified to get the GPS data from the STR-2770 GPS simulator system. So, the synthesized logic circuit is shown be accurately performed.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.589-597
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• 2023

Floating debris in large quantities from land during heavy rainfall has adverse social, economic, and environmental impacts, but the monitoring system for the concentration area and amount is insufficient. In this study, we proposed an efficient monitoring method for floating debris entering the river during heavy rainfall in Daecheong Lake, the largest water supply source in the central region, and applied remote sensing techniques to estimate the standing-stock of floating debris. To investigate the status of floating debris in the upper of Daecheong Lake, we used a tracking buoy equipped with a low-orbit satellite communication terminal to identify the movement route and behavior characteristics, and used a drone to estimate the potential concentration area and standing-stock of floating debris. The location tracking buoys moved rapidly during the period when the cumulative rainfall for 3 days increased by more than 200 to 300 mm. In the case of Hotan Bridge, which showed the longest distance, it moved about 72.8 km for one day, and the maximum moving speed at this time was 5.71 km/h. As a result of calculating the standing-stock of floating debris using a drone after heavy rainfall, it was found to be 658.8 to 9,165.4 tons, with the largest amount occurring in the Seokhori area. In this study, we were able to identify the main concentrations of floating debris by using location-tracking buoys and drones. It is believed that remote sensing-based monitoring methods, which are more mobile and quicker than traditional monitoring methods, can contribute to reducing the cost of collecting and processing large amounts of floating debris that flows in during heavy rain periods in the future.