• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1078-1084
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• 2010

The tracking performance of a big parabola tracking antenna system for tracking and receiving of the signal from the vehicle is impacted by many factors of the internal and the external of the system. In this paper, we analyze the tracking error due to the radio refraction in the application of the tracking and positioning of the vehicle by using radio frequency. The real measurement data are used for the analysis which had been acquired by using GPS and the tracking systems of C- and S-band frequencies in NARO Space centre. To verify the correlation between the tracking errors measured and the radio refraction, we review the error factors and the accuracies of the tracking systems, and the characteristics of the refractivity. The analysis shows that there are angular errors which are due to the radio refraction and not to be neglected, compared to the accuracies of the tracking systems, in case of low elevation angle less than 10 degrees. Also, the tracking errors depend on the target altitude as well as the elevation angle for the case of the target in the troposphere. It is recommended to correct the tracking angle considering the target altitude and elevation angle for the precise target positioning.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.1
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• pp.49-54
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• 2013

Japan and South Korea since 2004 until now for the broadcast channel interference, by measuring the ongoing conflict are expected to prepare for the future, but Korea's preparation are not enough. In this study, it is pointed that cause of the interference through channel environmental analysis, and effective application of propagation prediction model was carried out between neighboring countries. Between Korea and Japan, radio duct occurs on hold due to changes in the refractive gradient, and comfirmed occurrence of broadcasts interference. The results are presented that 1% time variable, -91.80 [N-units/km], 10% time variable, -43.92 [N-units/km], 50% time variable, -586.19 [N-units/km], for effective refractive gradient. Proposed refractive gradient could contribute to actual radio propagation prediction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.188-197
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• 2016

In this paper, we propose a method that represents a mathematical form of wave propagation by using the fact the refractive index determining wave propagation characteristic is a function of altitude. Proposed method uses Snell's law that expresses relationship between incident angle and refraction angle when incident wave passes medium having a different refractive index. We present the simulation results about wave propagation by setting the square of refractive index in the form of the polynomial for altitude and show that it is possible to estimate the coefficients of the polynomial through the angle information from vertical axis of multiple radar systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.1023-1026
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• 2016

We calculate the propagation characteristic of antennas considering refractive indices of space environments. The effective indices of troposphere, stratosphere, and inonshpere are computed and the ray tracing method, geometrical optics, and Huygens' principle are used to estimate refracted and attenuated electromagnetic wave of space environment.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.123-125
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• 2007

본 논문에서는 유한한 유전체 격자구조에 수직으로 입사되는 전자기파가 갖는 유효 굴절율을 구하고자 한다. 유전체 격자구조를 다층구조로 모델링하여 모드에 따른 전파상수를 계산하면 주어진 주파수에 따른 유효 굴절율을 계산할 수 있다. 다층구조에서 유효 굴절율을 계산을 응용하면 유전체 모양이나 구조에 따른 유효굴절율을 계산할 수 있으며 주파수 선택특성이나 도파관등에 진행모드 계산에 도움이 될 것으로 사료된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1076-1083
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• 2017

This paper discusses the error estimation in radar measurement data obtained while tracking a launch vehicle. It is known that typical radar measurement data consist of the true positional or orientation information on the vehicle being tracked, random noise and a deterministic bias due to radio refraction. Unlike previous research works, this paper proposes a tracking-error (mainly bias) estimation method solely based on the single radar measurement with no aid of other measurement such as GPS. The proposed method has been verified with real measurement data obtained while tracking the KSLV-I launch vehicle.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.6
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• pp.53-61
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• 2014

For monitoring the flight trajectory and the status of a launch vehicle, the mission control system in NARO space center process data acquired from the ground tracking system, which consists of two tracking radars, four telemetry stations, and one electro-optical tracking system. Each tracking unit exhibits its own tracking error mainly due to multi-path, clutter and radio refraction, and by utilizing only one among transmitted informations, it is not possible to determine the actual vehicle trajectory. This paper presents a way of generating flight trajectory via post-processing the data received from the ground tracking system. The post-processing algorithm is divided into two parts: compensation for atmosphere radio refraction and multi-sensor fusion, for which a decentralized Kalman filter was adopted and implemented based on constant acceleration model. Applications of the present scheme to real data resulted in the flight trajectory where the tracking errors were minimized than done by any one sensor.

• Journal of the Korean earth science society
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• v.40 no.1
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• pp.9-23
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• 2019

Super-refraction of radar beams tends to occur primarily under a particular vertical structure of temperature and water vapor pressure profiles. A quality control process for the removal of anomalous propagation (AP) ehcoes are required because APs are easily misidentified as precipitation echoes. For this purpose, we collected X-band polarimetric radar parameters (differential reflectivity, cross-correlation coefficient, and differential phase) only including non-precipitation echoes (super-refraction and clear-sky ground echoes) and precipitation echoes, and compared the echo types regarding the relationships among radar reflectivities, polarimetric parameters, and the membership functions. We developed a removal algorithm for the non-precipitation echoes using the texture approach for the polarimetric parameters. The presented algorithm is qualitatively validated using the S-band Jindo radar in Jeollanam-do. Our algorithm shows the successful identification and removal of AP echoes.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.40-46
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• 1999

We present a new modified effective index method which can be used to analyze lightwave circuit devices in 3-dimensional structure fast and accruatly using 2-dimensional BPM (beam propagating method). This method can analyze the devices with the cross-section of rectangular, ridge, or similar shapes accurately but more quickly than the 3-dimensional BPM, which is impractical to use on account of long calculating time. As an example, we showed that the calculation error of coupling length in a directional coupler by this method is significantly less than the 2-dimensional BPM using the effective index method.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.220.2-220.2
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• 2012

대기 중 수증기의 불규칙한 분포와 운동은 대기의 굴절율을 시간에 따라 불규칙하게 변화시킨다. 전파 관측 중 대기의 굴절율이 짧은 시간 동안에 크게 변하면 천체가 안테나 주빔의 중앙에서 벗어나는 것처럼 관측되고, 이는 마치 안테나 지향 오차가 커지는 것과 같은 효과를 준다. 이러한 현상을 대기 난굴절(Anomalous Refraction)이라고 한다. KVN 안테나 성능 시험 관측 중 심할 경우 수십초의 시간 규모에서 수십 각초 이상 안테나 지향 오차가 커지는 현상이 관측되어 각 사이트의 대기 난굴절 특성에 대하여 모니터링을 시행하였다. 22GHz와 43GHz에서 KVN 사이트의 대기 난굴절 특성을 파악하기 위하여 2010년 4월부터 2011년 4월까지 각 계절마다 세 사이트에서 시험 관측을 진행하였다. 관측 결과로부터 계절별, 낮과 밤등을 기준삼아 KVN 사이트의 대기 난굴절의 특성을 소개한다.