• Proceedings of the KIEE Conference
• /
• 2007.11c
• /
• pp.179-182
• /
• 2007

The Design and Optimization of a low-profile antenna for the Satellite Digital Audio Radio System(SDARS) using a Non-Dominated Sorting Genetic Algorithm(NSGA) is presented. a fairly omni-directional elevation gain pattern over 60 degrees < q <60 degrees are obtained. The average value of the LCP gain pattern is approximately 2 dBic. The heights of the antennas are less than 0.251. The cross polarized signal level is approximately 12 dBic less than the co-polarized signal level.

• Journal of Positioning, Navigation, and Timing
• /
• v.12 no.1
• /
• pp.83-89
• /
• 2023

The Korea Augmentation Satellite System (KASS) system is a Satellite Based Augmentation System (SBAS) under development to provide APV-I SBAS service in the Republic of Korea. The KASS ground segment generates correction and integrity information for GPS measurements of KASS users using the accurate positions of KASS Reference Station (KRS) antenna phase centers. For this reason, the accuracy of KRS reference points through geodetic survey campaigns is one of the important factors for providing the KASS service in compliance with the required navigation performance. In order to obtain accurate positions, two geodetic survey campaigns were performed at several reference points, such as Mark, Center of Mast at Ground Level (CMGL), and Center of Hole in Top Plate (CHTP), of each KRS site using three different survey methods, the Virtual Reference Station (VRS), Flächen Korrektur Parameter (FKP), and raw data post-processing methods. By comparing and analyzing the results, the computed coordinates of the reference points were verified and Antenna Phase Center (APC) positions were calculated using KRS Antenna Reference Point (ARP) data, and the first KASS Site Acceptance Test (SAT#1) was performed successfully using the verified APC coordinates. After the first site survey activities, the KASS operators should maintain the coordinates with the required performance such that the overall KASS navigation performance commitment is guaranteed during the lifetime of 15 years. Therefore, the maintenance plan for the KRS antenna coordinates should be developed before the commissioning of KASS operation planned after 2023. Therefore, this paper presents a geodetic survey method selected for the maintenance activities and provides the rationale for using this method.

• ETRI Journal
• /
• v.34 no.5
• /
• pp.767-770
• /
• 2012

This letter presents a novel compact circularly polarized patch antenna for Global Positioning System/Global Navigation Satellite System (GPS/GLONASS) applications. The proposed antenna is composed of a simple square radiating patch fed by a capacitive dual-feeder to increase the impedance bandwidth and a lumped element hybrid coupler to achieve the broadband characteristic of the axial ratio (AR). The realized antenna dimensions are $28mm{\times}28mm{\times}4mm$, which is the most compact size among the dual-band GPS/GLONASS antennas reported to date. The measured results demonstrate that the proposed antenna has a gain of 2.5 dBi to 4.2 dBi and an AR of 0.41 dB to 1.51 dB over the GPS/GLONASS L1 band (1.575 GHz to 1.61 GHz).

• Journal of Aerospace System Engineering
• /
• v.10 no.2
• /
• pp.1-6
• /
• 2016

The thermal analysis of electronic equipment is required to predict the reliability of electronic equipment being loaded on a satellite. The transient heat transfer of electronic equipment that was developed recently has been generated using a large-scale integration circuit. If there is a transient heat transfer between EEE(Electric, Electronic and Electro mechanical) parts, it may lead to failure the satellite mission. In this study, we performed the thermal design and analysis for reliability of APD(Antenna Pointing Driver) electronics for activation of a spaceborne X-band 2-axis antenna. The EEE parts were designed using a thermal mathematical model without the thermal mitigation element. In addition, thermal analysis was performed based on the worst case for verifying the reliability of EEE parts. For the thermal analysis results, the thermal stability of electronic equipment has been demonstrated by satisfying the de-rating junction temperature.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.54 no.3
• /
• pp.180-185
• /
• 2005

Microstrip antennas generally have a lot of advantages that are thin profile, lightweight, low cost, and conformability to a shaped surface application with integrated circuitry. In addition to military applications, they have become attractive candidates in a variety of commercial applications such as mobile satellite communications, the direct broadcast system (DBS), global positioning system (GPS), and remote sensing. Recently, many of the researches have been achieved for improving the impedance bandwidth of microstrip antennas. The basic form of the microstrip antenna, consisting of a conducting patch printed on a grounded substrate, has an impedance bandwidth of $1\~2\%$. For improvement of narrow bandwidth of microstrip patch, we were designed U-slot microstrip patch antenna in this paper. This antenna had wide bandwidth for all personal communication services (PCS) and IMT-2000. For the design of U-slot microstrip patch antenna using a finite difference time domain(FDTD) method. This numerical method could get the frequency property of U-slot patch antenna and the electromagnetic fields of slots.

• Journal of Satellite, Information and Communications
• /
• v.5 no.2
• /
• pp.75-81
• /
• 2010

COMS (Communication, Ocean and Meteorological Satellite) is the multi-purposed Korean geostationary satellite funded by four Korean government ministries, and is to supply communication services, ocean and weather observation for 7 years. As part of COMS, development of Ka band communication payload composed of microwave switching transponder and multi-horn antenna is sponsored by KCC (Korea Communications Commission) and developed by ETRI (Electronics and Telecommunications Research Institute). The purpose of Ka Payload development is to acquire space proven technology of Ka payload and to exploit advanced multimedia communication services. This paper aims to study development technology of Ka payload system through whole process of ETRI project. Also application of Ka payload will be dealt in this paper.

• Journal of Satellite, Information and Communications
• /
• v.12 no.1
• /
• pp.43-48
• /
• 2017

Recently, demands on civilian UAV (Unmanned Aerial Vehicle) has been increasing and appropriate communication system is required for the UAV. In this paper, the performance of the UAV communication system using commercial wireless mobile network is discussed. The main service area of the wireless mobile network is ground level however the flying range of the UAV is normally in high altitude. Because of this mismatch of service area the performance of the UAV communication system is degraded in high altitude. To compensate performance degradation of the UAV communications system in high altitude, adaptive array antenna is introduced which is able to overcome altitude limitation of the UAV communication system.

• Korean Journal of Remote Sensing
• /
• v.23 no.2
• /
• pp.137-144
• /
• 2007

In KORDI (Korea Ocean Research and Development Institute), the KOSC (Korea Ocean Satellite Center) construction project is being prepared for acquisition, processing and distribution of sensor data via L-band from GOCI (Geostationary Ocean Color Imager) instrument which is loaded on COMS (Communication, Ocean and Meteorological Satellite); it will be launched in 2008. Ansan (the headquarter of KORDI) has been selected for the location of KOSC between 5 proposed sites, because it has the best condition to receive radio wave. The data acquisition system is classified into antenna and RF. Antenna is designed to be $\phi$ 9m cassegrain antenna which has 19.35 G/T$(dB/^{\circ}K)$ at 1.67GHz. RF module is divided into LNA (low noise amplifier) and down converter, those are designed to send only horizontal polarization to modem. The existing building is re-designed and arranged for the KOSC operation concept; computing room, board of electricity, data processing room, operation room. Hardware and network facilities have been designed to adapt for efficiency of each functions. The distribution system which is one of the most important systems will be constructed mainly on the internet. and it is also being considered constructing outer data distribution system as a web hosting service for offering received data to user less than an hour.

• Aerospace Engineering and Technology
• /
• v.6 no.1
• /
• pp.157-164
• /
• 2007

For a GPS antenna to normally receive GPS satellite signals during full flight mission of a satellite launch vehicle, it should be installed on skin of the vehicle. The surface of a launch vehicle is drastically heated up due to aerodynamic heating effect during flight, so that the GPS antenna mounted on surface of the launch vehicle is directly exposed to extremely hot temperature environment. Hot temperature test specification of the GPS antenna, therefore, is severer than inner components. This paper describes that procedures and results of performance analysis of the GPS antenna for KSLV-I under hot temperature environment. The GPS antenna was not deformed physically and inner LNA(Low Noise Amplifier) operated normally without performance degradation.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.11
• /
• pp.1042-1048
• /
• 2012

A 2-axis gimbal system is one of main disturbance sources affecting image jitter response of a satellite. The gimbal system comprises azimuth stage and elevation stage, and these pointing mechanism can be rotated by stepping motors about its azimuth and elevation axes simultaneously. Because of the complex and coupled dynamic motion of the gimbal system, its moment of inertia and structural modes can be changed according to the system configuration, and thus the gimbal system generates complicated and non-linear disturbance characteristics. In order to improve the jitter response of a spacecraft, it is an indispensable process to reduce the micro-vibration disturbance level of the antenna system. In the present research, a 2-axis gimbal system was manufactured and then its micro-vibration test was performed in terms of two types of stepping motors(2-phase and 5-phase). The test results show that the disturbance level of the gimbal system can be reduced by replacing the 2-phase stepping motor with the 5-phase one, and the average disturbance attenuation ratio is 56 % in peak level and 48 % in standard deviation level. The experimental results confirm that it is an efficient jitter reduction method to adopt a high-phase stepping motor.