• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.312-318
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• 2014

The altitudes of GEO satellites are higher than those of GPS satellites. Therefore the visibility and the received power of GPS signals are totally different from those of the users near the Earth's surface. In this study, we analyzed the visibility of GPS signals received on GEO satellites. And we also developed a software GPS receiver that works on GEO satellites using CCMDB algorithm which is a weak signal receiver algorithm. GPS signals received on a GEO satellite are generated by a commercial hardware GPS simulator and used for the verification of the developed software GPS receiver. The mean 3D position and velocity error are calculated as 165.636 m and 0.5081 m/s.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.1
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• pp.94-101
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• 2007

Streaming video is expected to become a key service in the developing heterogeneous wireless network. However, sufficient quality of service is not offered to video applications because of bursty packet losses. An effective solution for packet loss in wireless network is to perform a proper concealment at the receiver. However, most concealment methods can not conceal effectively the consecutively damaged macro blocks, since the neighboring blocks are lost. In the previous work, bidirectional motion vector tracking (BMVT) method has been proposed which uses the moving trajectory feature of the damaged macro blocks. In this paper, a channel-adaptive redundancy coding method for the better BMVT error concealment is presented. The proposed method provides enhanced video quality at the cost of a little bit overhead in the wireless error-prone network.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.38-44
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• 2011

Because of the complexity of the underwater environment, the communication has difficulties that can differ significantly from those in air, The signal is degraded by many random noises. Furthermore, the limit of the bandwidth is a big issue in underwater communication. Therefore, the array signal processing can be adapted to improve the signal-to-noise ratio. In this paper, we propose a potential method for underwater communication based upon source tracking techniques. Also, a new tracking model by using a multi-array sonar and detail of the multi-array sonar configuration are shown in this paper. The experiment results demonstrated the receiver configuration is very potential to solve communication problems, especially in the underwater environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8B
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• pp.1593-1600
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• 1999

This paper describes the acquisition modeling of an airborne target for target tracking simulation of infrared homing missiles. The modeling, of which key technologies are the sub-modeling for target infrared signature, atmospheric transmission, and receiver characteristics, shows the acquisition process of an airborne target under various tracking conditions determined by line-of-sight, distance, and atmospheric conditions. We confirm the validity of the modeling by applying it to simulations concerned with target tracking. The modeling gives a guideline to determine an optimum detector and a defection band for effective discrimination of the target among false targets.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10C
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• pp.1016-1023
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• 2009

In this paper, a tracking bias compensation method is proposed for future global navigation satellite systems (GNSSs). It is observed that the correlation function of a GNSS signal has many peaks and remains almost unchanged in the advanced offset region as a result of the multipath signals arriving at the receiver later than a line-of-sight signal. Based on these observations, we use the slopes in the advanced offset region to compensate for the code tracking bias, and obtain the maximum code tracking bias, which is essential to implement the proposed scheme, in static multipath environments. Finally, it is demonstrated that the proposed compensation method is very effective for the GNSS signal tracking in terms of the code tracking biases and their running averages.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.5
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• pp.71-77
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• 2020

Recently, the tracking radar has confirmed the necessity of developing a small tracking radar that can be operated without various restrictions in various environments. In addition, the performance of a small tracking radar requires equal to or higher than the existing tracking radar. Such a small tracking radar can be implemented through miniaturization and low power of existing tracking radar. In this paper, the role and function of a signal processor for a small tracking radar are defined and we proposed a method to increase the efficiency of power consumption and miniaturization by minimizing the use of devices required to implement a signal processor for a small tracking radar. Used as a method for miniaturization, a device processor such as DDC and communication controller was implemented in an FPGA to design a signal processor for a small tracking radar. In addition, a low-power signal processor was designed by a power supply using a highly efficient switching regulator. Finally, the signal processor was verified by the performance test of the signal processor for the small tracking radar implemented, the Doppler tracking test using the signal processor on the small tracking radar, and the distance tracking test.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.905-913
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• 2006

In the impulse radio ultra-wideband communication systems, the residual timing offset exists when the acquisition and tracking of the timing synchronization is well done. And the offset affects the performance of the system dramatically. In order to compensate the offset, we present the digital phase-locked loop that uses the reference signal in the correlation detection receiver. First, we show the degradation of BER performance that is caused by the offset, and then compensation process of the timing tracker and performance improvement. In this paper, the timing detector in the tracker operates at the sampling period of frame level uses the correlation between received and reference signal. Also, we present the performance comparison by using the computer simulation results for different Gaussian monocycle pulses.

• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.80-88
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• 2011

Heliostat in the tower type solar thermal power plant is a sun tracking mirror system to reflect the solar energy to the receiver and the optical performance of it affects to the efficiency of whole power plant most significantly. Thus a solid understanding of heliostat's energy concentration characteristics is the most important step in designing of the heliostat field and the whole power plant. The work presented here is the analysis of energy concentration characteristics of heliostat used in 200kW solar thermal power plant, where the receiver located at 43m high in tower has $2{\times}2$m rectangular shape. The heliostat reflective surface is formed by 4 of $1{\times}1$m flat plate mirror facet and the mirror facet is mounted on the spherical frame. The direct normal incident radiation models in vernal equinox, summer solstice, autumnal equinox and winter solstice are first derived from the actually measured data. Then the intercept ratio, heat flux distribution and total energy collected at the receiver for the heliostats located in the various places of the heliostat field are investigated. Finally the effect of mirror facet installation error on the optical performance of the heliostat is analyzed.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.7
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• pp.695-701
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• 2008

In this paper, we propose the efficient Doppler removal method using map-based partial-time common intermediate frequency removal technique. In the proposed algorithm, the 2-stage carrier removal process was used. First, the component of common intermediate frequency is removed. Next the component of Doppler was removed with averaging and approximation. For the evaluation of the proposed algorithm, The real-time software GPS L1 C/A-code receiver was implemented. When the proposed algorithms are used, 12 tracking channels with 3 track arm(early, prompt, late) is operated real-time on PC using a Intel Pentium-III 1.0GHz CPU. Also, the requirement of memory was less than 2Mbytes. The real-time software GNSS receiver using the proposed algorithms provides the navigation solution with below 10 meter rms error. Especially, in spited of using the various approximations for implementing the algorithms, the high sensitivity capability (able to track the weak signal with -159dBm) was achieved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.745-752
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• 2005

In this paper we propose and implement a digital part of a receiver system for identifying a moving object and its tracking position in wireless environment. We assumed UWB(Ultra Wide Band)-based communication system for target application and used serial communication method(RS-232). The proposed digital receiver consists of RS-232-type1/RS-232-type2 for input and output of serial communication, ID Detector for detecting IDs, and PISO&Buffer circuit to buffer input signals for appropriate operation of ID Detector. We implemented the digital receiver with minimal hardware(H/W) resource according to target application of UWB-based communication system. So it correlates input patterns with pre-stored patterns though repeated detecting method for multiple IDs. Since it has reference panerns in the Ve-stored form, it can detect various IDs instantly. Also we can program content and size of reference patterns considering compatibility with other systems .The implemented H/W was mapped into XC2S100PQ208-5 FPGA of Xilinx, occupied 727($30\%$) cells, and stably operated in the clock frequency of 75MHz(13.341ns).