• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.05a
• /
• pp.61-62
• /
• 2017

In this study, a circular polarization patch antenna operates at the wide bandwidth of 1.5GHz~1.7GHz was designed. To obtain the wide bandwidth and high gain, the high air substrate was applied. The impedance bandwidth is improved by adjusting the sizes of patch, the distance between main patch and ground plate, the length of internal slots, the position of feeding point, the length of external stub, etc. The antenna is designed by simulation for an operation in the frequency range of 1.5GHz~1.7GHz band, and the antenna characteristics such as return loss, gain, radiation patterns are examined.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.5
• /
• pp.2004-2010
• /
• 2018

We propose a small active antenna to receive Global Navigation Satellite System (GNSS) signals, i.e., Global Positioning System (GPS) L1 (1,575MHz) and Russian Global Navigation Satellite System (GLONASS) L1 (1,600 MHz) signals. A two-stage low-noise amplifier (LNA) with more than 27 dB gain is implemented in the bottom layer of a three-layer antenna package. In addition, a hybrid coupler is used to combine signals from pair of proximately coupled orthogonal feeds with $90^{\circ}$ phase difference to achieve the circular polarization (CP) characteristic. Three layers of high permittivity (${\varepsilon}_r=10$) substrates are stacked and effectively integrated to have a small dimension of $64mm{\times}64mm{\times}7.42mm$ (including both circuit and antenna). The reflection coefficient of the fabricated antenna at the target frequency is below -10 dB, the measured antenna gain is above 26 dBic and the measured noise figure is less than 1.4 dB.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.2
• /
• pp.117-122
• /
• 2006

Modernized GNSS such as new GPS signals updated GLONASS and coming Galileo promises higher quality and higher reliability for users. Powerful technologies such as Internet, ubiquitous network technology and sensor network has been used to promote a safe and more secure lifestyle. This report describes experimental trials to combine these technologies namely GPS and Sensor Network into a high-performance system. GPS is used to enlarge the communication range, resolving the service area limitations, as a wider service area is required at shore areas compared to urban area. GPS position datum is also used as primary network routing information to get practical Sensor Network. Another application is the under water Sensor Network. Accurate GPS position and time are used to establish stable and high reliability underwater acoustic Sensor Network. This paper describes the background of the project 'Harbor area Marine Ubiquitous Sensor Network', preliminary consideration and testing. Radio and acoustic communication is the main focus of this preliminary experiment.

• Journal of Positioning, Navigation, and Timing
• /
• v.7 no.4
• /
• pp.189-203
• /
• 2018

In this paper, a Software Defined Radio (SDR) architecture was designed and implemented for rapid prototyping of GNSS receiver. The proposed SDR can receive various GNSS and direct sequence spread spectrum (DSSS) signals without software modification by expanded input parameters containing information of the desired signal. Input parameters include code information, center frequency, message format, etc. To receive various signal by parameter controlling, a correlator, a data bit extractor and a receiver channel were designed considering the expanded input parameters. In navigation signal processing, pseudorange was measured based on Coordinated Universal Time (UTC) and appropriate navigation message decoder was selected by message format of input parameter so that receiver position can be calculated even if SDR is set up various GNSS combination. To validate the proposed SDR, the software was implemented using C++, CUDA C based on GPU and USRP. Experimentation has confirmed that changing the input parameters allows GPS, GLONASS, and BDS satellite signals to be received. The precision of the position from implemented SDR were measured below 5 m (Circular Error Probability; CEP) for all scenarios. This means that the implemented SDR operated normally. The implemented SDR will be used in a variety of fields by allowing prototyping of various GNSS signal only by changing input parameters.

• Journal of Positioning, Navigation, and Timing
• /
• v.10 no.2
• /
• pp.103-111
• /
• 2021

A series of experiments have been carried out by using National Geographic Information Institute(NGII)'s Continuously Operating Reference Station (CORS) data with various strategies to analyze the impact of multi-GNSS measurements on baseline processing. The results of baseline processing were compared in terms of ambiguity fixing rate, precision, and hypothesis tests were conducted to confirm the statistical difference. The combination of multi-GNSS measurements has helped to improve ambiguity fixing rate, especially under harsh positioning environments. Combination of GPS, Galileo, BeiDou could get better precision than that of GPS, GLONASS, Galileo, and adding QZSS made the baseline solution's vertical component more precisely. The hypothesis tests have statistically confirmed that the inclusion of the multi-GNSS in the baseline processing enables not only to reduce field observation time length but also to enhance the solution's precision. However, it is of interest to notice that results of the baseline solution are dependent upon the software used. Hence, comprehensive studies should be performed shortly to derive the best practice to select the appropriate software.

• Journal of Positioning, Navigation, and Timing
• /
• v.10 no.4
• /
• pp.279-289
• /
• 2021

GNSS receivers capable of tracking multiple Global Navigation Systems (GNSSs) simultaneously are widely used. In order to estimate accurate user position and velocity, it is necessary to consider the key elements that contribute to the interoperability of the different GNSSs. Typical examples are the time system and the coordinate system. Each GNSS is operated based on its own reference time system depending on when the system was developed and whether the leap seconds are applied. In addition, each GNSS is designed based on its own coordinate system based on earth model constant values. This paper addresses the interoperability issues from the viewpoint of Single Point Positioning (SPP) users utilizing multiple GNSS signals from GPS, GLONASS, BeiDou, and Galileo. Since the broadcast ephemerides of each GNSS are based on their own time and coordinate systems, the time and the coordinate systems should be unified for any user algorithm. For this purpose, this paper proposes a method of converting each GNSS coordinate system into the reference coordinate system through Helmert transformation. The error of the broadcast ephemerides was calculated with the precise ephemerides provided by the International GNSS Service (IGS). The effectiveness of the proposed multi-GNSS correction and transformation method is verified using the Multi-GNSS Experiment (MGEX) station data.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.29 no.3
• /
• pp.311-318
• /
• 2011

On March 11, 2011, an 9.0-magnitude earthquake occurred near the northeastem coast Japanese. It was the largest earthquake that hit Japan since the beginning of modern seismometry. The earthquake occurred 179km east of the Sendai, Miyagi Prefecture, leaving about 27,000 of people confirmed dead, injured or missing due to the earthquake and tsunami. In this study, crustal Deformation in Mizusawa, Tsukuba and Usuda station were calculated based on GPS data in IGS station of Japan. The observation data were processed by precise point positioning and relative-positioning method using on-line GPS data processing services and a high precision scientific GPS/GLONASS data processing software. The coseismic displacements in IGS stations before and after the earthquake were analyzed using kinematic precise point positioning method, and the crustal deformation of the areas before and after the earthquake were precisely calculated using the relative-positioning method. The results of the study calculated precise coordination that the RMSE is maximum ${\pm}0.003m$, respectively and showed that Mizusawa station moved 2.6m southeast by the earthquake.

• Journal of Navigation and Port Research
• /
• v.37 no.3
• /
• pp.263-267
• /
• 2013

This paper describes the progress and the plan of 'Wide Area Differential GPS (WA-DGPS) Development' project supported by Korean Ministry of Oceans and Fisheries. The project develops the main algorithms of the WA-DGPS which guarantees the improved accuracy, availability, and integrity all over the Korean peninsula. After the establishment of WA-DGPS ground infrastructure system, a real-time demonstration using pseudolite installed on the ground will be conducted in the final year. Also, the development of Korean Satellite-based Augmentation System (SBAS) is expected to be started from 2014, and the algorithms and the results in the WA-DGPS project will be used in the SBAS development.

• Journal of Advanced Navigation Technology
• /
• v.20 no.5
• /
• pp.417-424
• /
• 2016

Russia recently began broadcasting the SDCM signal in order to provide SBAS service for the civil aviation in the Russian territory using its own geostationary satellites. The service coverage of the SDCM geostationary satellite, LUCH-5A and LUCH-5B, includes Korea peninsula, where the test signal from the pseudo random number (PRN) 140 is received. This paper shows that the position accuracy at the Chulwon GNSS site is improved to 0.8749 m (horizontal) and 0.9589 mm (vertical) by applying the received SDCM message to the RINEX data. Considering that the SDCM augments both GPS and GLONASS, the performance of multi-constellation SBAS was compared to that of GPS-only SBAS, and APV-I availability was improved by decreasing the protection level about 30 %. From the results, we can expect that the mult-constellation SBAS can contribute to the performance enhancement of the future KASS.

• Journal of Advanced Navigation Technology
• /
• v.17 no.4
• /
• pp.396-403
• /
• 2013

Recently, GNSS users can utilize various navigation satellite thanks to GPS modernization, renewal of GLONASS, and development of Galileo and Beidou. And availability performance of users is expected to be improved because these new navigation satellites transmit L5 signal as well as L1 signal, and users can directly estimate the ionospheric delays. In accordance with these changes existing Satellite Based Augmentation System (SBAS) which considers only GPS L1 signal is being developed to support dual frequency and multi-constellation GNSS users. This paper describes the main features of dual-frequency, multi-constellation SBAS algorithms and estimates the performance in Korean region by simulation.