• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.868-875
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• 2000

GPS(Global Positioning System) is widely used in the navigation system, ITS(Intelligence Transportation System), and mobile communications. Recently, it is considered to combine the GPS receiver with the CLONASS for the improvement of performance and accuracy. In this paper, a wideband aperture-coupled patch antenna with circular polarization is designed and implemented for the use of CPS/GLONASS combined receiver. The measured characteristics of the manufactured antenna shows the - l5 dB bandwidth of 220 MHz and the axial ratio less than 2.1 dB, and it satisfies the requirements of the GPS/GLONASS antenna.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.48-52
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• 2007

Recently, the research of GPS receiver which uses the Software-Defined Radio(SDR) technique is being actively proceeded instead of traditional hardware-based receiver. The software-based GPS receiver indicates that the signal acquisition and tracking treated by the hardware-based platform are processed as the software technique through a microprocessor. In this paper, GPS software receiver is designed by using SDR technique and then the signal acquisition, tracking, and the navigation message decoding parts are verified through the PC-based simulation. Moreover, the efficient algorithms are developed about the signal acquisition and tracking parts in order to obtain the accurate pseudorange. Finally, the pseudorange is calculated through the relative channel delay received through the different satellite of L1 frequency band. GPS software receiver proposed in this paper will be included in the element of GPS/Galileo complex system of development target and will provide not only the method that verifies the performance for Galileo Sensor Station standard but also usability by providing various debugging environments.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.90-101
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• 1995

We determined three dimensional precise WGS 84 corrdinates of two points in Bohyunsan Optical Astronomy Observatory using the GPS. One of the two points is the center on the top of pier for 1.8m telescope, and the other one is placed on the hill beside the dome of 1.8m telescope. We performed the simultaneous GPS observation at the KAO GPS station and Bohyunsan Obervatory for 5 days from December 18 to 22, 1993. We employed three Trimble 4000SST receivers for these observations. The observed data were processed by TRIMVEC-PLUS software of Trimble with the MBPS method and the Triple Difference L1/L2 ION free technique. Through this research, we determined WGS 83 latitude, longitude and height of 1.8m telescope in Bohyunsan Optical Astronomy Observatory with the values of $36^{circ}9'53".1943N\pm0."0018,\;128^{circ}58'35".6829E\pm0."0029,\;1162.47m\pm0.04m$, respectively.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.2
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• pp.163-172
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• 1994

As for the baseline measurement using geodetic GPS receiver, this paper puts forth the effective measurement range of a low-priced GPS system receiving Ll frequency only. Compared with the data of baseline eliminated the ionospheric effects with L1/L2 frequencies, the results with Ll frequency approximate to those with dual frequency within the range of 15 km (the baseline discrepancy of the two methods is less than 2 cm). The results with Ll frequency are better within the range of 18 km. Based upon the analysis of data, we find that the convergence limit of integer ambiguity-applicable to double difference fixed solution- is about 18 km and the ionospheric effects have a great influence on the results when the baseline are longer than 20 km. This study also presents a standard which makes it possible to select the favorable data from the results of the GPS relative distance measurements.

• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.319-326
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• 2009

In this paper, the key technologies of Navigation receiver for GNSS sensor station are presented as a development result of a GNSS ground station in ETRI. A wide-band antenna and RF/IF components and SW signal processing unit to cover the GPS and Galileo signals for GNSS receiver are developed and its performance is verified by using GPS live signal and GNSS RF signal simulator from SpirentTM. We also gather GIOVE-A signal by using H/W antenna and RF/IF units in IF-level as sampling frequency and bit number, 112MHz and 8bits, respectively by using the developed wide-band antenna and RF/IF components. Data acquisition is done by using commercial data acquisition device from National Instrument TM. The gathered data is fed into SW receiver to process Galileo E1 to verify Galileo signal processing by Galileo live signal from GIOVE-A.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.129-140
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• 2004

KAO(Korea Astronomy Observatory) GPS group has developed an iRTK system as a near-real time positioning system using GPS carrier phase data. We focused on improving the accuracy of positioning through the updated capability of data processing of KAO's iRTK system using low-cost L1 carrier phase receiver. The accuracy of a positioning was demonstrated by Extended Kalman filter. Experiments were accomplished using from 30m to 20km baselines. Within 10km, the positioning accuracy was improved by approximately 50-70% to the previous study using one minute observable data. However, it took two minutes to obtain 1m level positioning accuracy at 20km point. We expect that the developed iRTK system can be applied to the various fields of GPS in near-real time positioning.

• Journal of Broadcast Engineering
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• v.21 no.5
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• pp.803-815
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• 2016

In this paper, we design a direct radio frequency (RF) sampling receiver for multiband GNSS signals and demonstrate its performance. The direct RF sampling is a technique that does not use an analog mixer, but samples the passband signal directly, and all receiver processes are done in digital domain, whereas the conventional intermediate frequency (IF) receiver samples the IF band signals. In contrast to the IF sampling receiver, the RF sampling receiver is less complex in hardware, reconfigurable, and simultaneously converts multiband signals to digital signals with an analog-to-digital (AD) converter. The reconfigurability and simultaneous reception are very important in military applications where rapid change to other system is needed when a system is jammed by an enemy. For simultaneous reception of multiband signals, the sampling frequency should be selected with caution by considering the carrier frequencies, bandwidths, desired intermediate frequencies, and guard bands. In this paper, we select a sampling frequency and design a direct RF sampling receiver to receive multiband global navigation satellite system (GNSS) signals such as GPS L1, GLONASS G1 and G2 signals. The receiver is implemented with a commercial AD converter and software. The receiver performance is demonstrated by receiving the real signals.

• Journal of Astronomy and Space Sciences
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• v.11 no.1
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• pp.71-80
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• 1994

It is generally known that the measurement of the ionospheric total electron content(TEC) by GPS can more accurately monitor the broader area of the ionosphere than other current methods. \Ve measured the TEC along a slant path considering the arrival time differences of P-code which is transmitted from GPS satellites with the modulation on two L-band carrier frequencies, L1 (1574.42MHz) and L2 (1227.60MHz). Under the assumptions that the ionosphere is uniformly distributed and its average height is 350km, we transformed the slant TEC to the vertical TEC at the point that the line-of-sight direction to GPS satellite cut across the average height of the ionosphere. Because there is no dual frequency P-code GPS receiver in Korea, we used the data observed at the TAIW GPS station ($N25^{\circ},E121.5^{\circ}$) in Taiwan which is one of the core stations in International GPS and Geodynamics Services (IGS). The TEC values obtained in this work showed a typical daily variation of the ionosphere which is high in the daytime and low in the nighttime. Our results are found to be consistent with the SOLAR-DAILY data of NOAA and the Klobuchar's model for the ionospheric correction of GPS. In addition, in the cornparision with SOLAR-DAILY data, we estimated the precision of our TEC measurement as 2 TEC.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.391-399
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• 2012

Multipath remains a dominant source of ranging errors in GNSS (Global Navigation Satellite System). And it is generally considered undesirable in the context of GNSS, since the reception of multipath can make significant distortion to the shape of the correlation function. In this paper, therefore, the model of the distorted shape of the correlation function is formulated and a MBME (Model-Based Multipath Estimation) technique for GPS L1/L5 receivers is proposed in order to estimate the parameters of the indirect signal such as the amplitude and the delay. The MBME technique does not require the any hardware modifications and it can estimate the parameters for both the short and long-delay multipath. Especially, it would be the very effective technique for the short-delay multipath if the L5 signal is available. Finally, the feasibility of the proposed technique has been confirmed by simulation results.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.71-76
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• 2015

In this paper, we developed the hardware GPS signal generator for generating a satellite navigation signal synchronized with Live GPS signal signals and analyzed the performance of signal genterator thorough the experiment For a hardware implementation of the GPS navigation signal synchronous generator, the GPS module may receive a GPS signal in order to generate the same signal as the operation that is transmitted from the current GPS satellite and the synchronized time information and the GPS satellites using the Novatel Inc. OEMStar.In. For generating the GPS synchronization signal, the GPS navigation signal generator was adjusted to a reference clock using the GPS clock synchronous information provided by the GPS receiving module and GPS signals also generated in consideration of the delay of the internal hardware of the generator. In this paper, we analyzed the effect of the receiver via the signal switching between Live GPS signal and generates a signal to measure the performance of the GPS navigation synchronization signal generator. It was confirmed that by the seamless operation of the signal even the moment that the switching of the generated signal from Live GPS signal has occurred through experimentation.