• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.275-275
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• 2000

This paper designs a digital correlator for the integrated GPS/GLONASS receiver consisting of DCO, carrier cycle counter, code generator, code phase counter, mixer, epoch counter, accumulator. It is designed using Verilog-HDL(Verilog-Hardware Description Language) and synthesized using EDA(Electronic Design Automation) tools. The performance of the designed digital correlator is verified by the functional simulation and real satellite tracking experiments.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.113.4-113
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• 2001

A 24 channel L1 C/A-code GPS attitude-finding receiver is designed and implemented. The performance of developed receiver is evaluated under the various environments. The results show that the performances from land and maritime test are almost same in the calm lake. And it follows the expected performance derived from an analysis. It is expected that the developed receiver can be used in not only maritime applications but also land and air applications where the heading is required.

• Journal of Biosystems Engineering
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• v.36 no.2
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• pp.116-121
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• 2011

This study was conducted to develop a robust navigator which could be in positioning for precision farming through developing a plural GPS receiver with 4 sets of GPS antenna. In order to improve positioning accuracy by integrating GPS signals received simultaneously, the algorithm for processing plural GPS signal effectively was designed. Performance of the algorithm was tested using a simulation program and a fixed point on WGS 84 coordinates. Results of this study are aummarized as followings. 1. 4 sets of lower grade GPS receiver and signals were integrated by kalman filter algorithm and geometric algorithm to increase positioning accuracy of the data. 2. Prototype was composed of 4 sets of GPS receiver and INS components. All Star which manufactured by CMC, gyro compass made by KVH, ground speed sensor and integration S/W based on RTOS(Real Time Operating System)were used. 3. Integration algorithm was simulated by developed program which could generate random position error less then 10 m and tested with the prototype at a fixed position. 4. When navigation data was integrated by geometrical correction and kalman filter algorithm, estimated positioning erros were less then 0.6 m and 1.0 m respectively in simulation and fixed position tests.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.7
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• pp.23-29
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• 2011

A dB-linearity improved variable gain amplifier (VGA) for GPS receiver is presented. The Proposed dB-linear current generator has improved dB-linearity error of ${\pm}0.15$dB. The VGA for GPS is designed using proposed dB-linear current generator and composed of 3 stage amplifiers. The IF frequency is assumed as 4MHz and the linearity requirement of the VGA for GPS receiver is defined as 24dBm of IIP3 using cascaded IIP3 equation and the VGA satisfies 24dBm when minimum gain mode. The DC-offset voltage is eliminated using DC-offset cancelation loop. The gain range is from -8dB to 52dB and the dB-linearity error satisfies ${\pm}0.2$dB. The 3-dB frequency has range of 35MHz~106MHz for the gain range. The VGA is designed using 0.18${\mu}m$ CMOS process. The power consumption is 3mW with 1.8V supply voltage.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1649-1654
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• 1991

In 1995 the VSOP satellite, which is called MUSES-B in Japan, will be launched under the VLBI Space Observatory Programme(VSOP) promoted by ISAS(Institute of Space and Astronautical Science) of Japan. We are now developing the GPS Receiver(GPSR) and On-board Orbit Determination System. This paper describes the GPS(Global Positioning System), VSOP, GPSR(GPS Receiver system) configuration and the results of the GPS system analysis. The GPSR consists of three GPS antennas and 5 channel receiver package. In the receiver package, there are two 16 bits microprocessing units. The power consumption is 25 Watts in average and the weight is 8.5 kg. Three GPS antennas on board enable GPSR to receive GPS signals from any NAVSTARs(GPS satellites) which are visible. NAVSATR's visibility is described as follows. The VSOP satellite flies from 1, 000 km to 20, 000 km in height on the elliptical orbit around the earth. On the other hand, the orbit of NAVSTARs are nearly circular and about 20, 000 km in height. GPSR can't receive the GPS signals near the apogee, because NAVSTARs transmit the GPS signals through the NAVSTAR's narrow beam antennas directed toward the earth. However near the perigee, GPSR can receive from 12 to 15 GPS signals. More than 4 GPS signals can be received for 40 minutes, which are related to GDOP(Geometric Dillusion Of Precision of selected NAVSTARs). Because there are a lot of visible NAVSTARs, GDOP is small near the perigee. This is a favorqble condition for GPSR. Orbit determination system onboard VSOP satellite consists of a Kalman filter and a precise orbit propagator. Near the perigee, the Kalman filter can eliminate the orbit propagation error using the observed data by GPSR. Except a perigee, precise onboard orbit propagator propagates the orbit, taking into account accelerations such as gravities of the earth, the sun, the moon, and other acceleration caused by the solar pressure. But there remain some amount of calculation and integration errors. When VSOP satellite returns to the perigee, the Kalman filter eliminates the error of the orbit determined by the propagator. After the error is eliminated, VSOP satellite flies out towards an apogee again. The analysis of the orbit determination is performed by the covariance analysis method. Number of the states of the onboard filter is 8. As for a true model, we assume that it is based on the actual error dynamics that include the Selective Availability of GPS called 'SA', having 17 states. Analytical results for position and velocity are tabulated and illustrated, in the sequel. These show that the position and the velocity error are about 40 m and 0.008 m/sec at the perigee, and are about 110 m and 0.012 m/sec at the apogee, respectively.

• Journal of Satellite, Information and Communications
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• v.6 no.1
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• pp.80-85
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• 2011

In this paper, a software-based real-time GPS L1 receiver is proposed for the block correlation techniques. Recently various navigation satellite navigation receivers in the environment for the development of more efficient software-based real-time receiver need to be developed. It is composed of components such as signal supplier, signal acquisition, signal tracking, navigation data processing, and navigation solution. They are designed and implemented as component based software for enhancing reusability and modifiability for user to have more flexibility during development of receiver. This paper will describe design, implementation, and verification of the developed realtime software GNSS receiver.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.9
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• pp.939-947
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• 2008

The GPS tracking loop consists of three parts in general: discriminator, loop filter and DCO (Digitally Controlled Oscillator). The loop filter is the main part of the tracking loop designed to ensure a good tracking performance. Generally, the loop filter is designed using classical PI(Proportional Integral) control. Although the carrier Doppler and code Doppler are generated by the same relative movement between the satellite and the user, often, the loop filters for each tracking loop are designed separately and independently. Sometimes, they are used in a combined manner such as carrier aided code tracking, FLL assisted PLL, etc. For better GPS signal tracking, we need to design the FLL/PLL/DLL altogether optimally. The purpose of this paper is to design a GPS receiver tracking loop based on the Kalman filter in a combined manner. Also, the proposed GPS receiver tracking loop is compared with a conventional tracking loop in terms of the transfer function and the DCO input. This paper shows that conventional tracking loop is equal to the Kalman filter based tracking loop.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.6
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• pp.446-455
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• 2001

In this paper, the precise synchronized clock generator using GPS receiver is presented. The GPS receiver provides a synchronized IPPS signal which guaranties a reliable standard time mark. This signal allows us to do time synchronization and correct the time step. We designed and implemented the precise synchronized clock generator based on DPLL in order to generate a high-resolution clock from a low-cost inaccurate oscillator with ALTERA FLEX EPM6016TC144-3. We also implemented a hardware unit and proved that the unit provides 1MHz clock output which had a high resolution and accuracy when it was combined with GPS receiver.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.2
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• pp.126-133
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• 2010

Due to the deployment of various wireless networks originating from CDMA, GSM, and WLAN, it became very convenient to exchange information from one place to another. As compared with the traditional environments for one-way information distribution based on fixed radio frequency bands, the convenient wireless network environments will bring about many changes in positioning technologies based on global navigation satellites. Among the many changes to come, the reconfigurable receiver network is one of the most attractive concepts since it can be tailored to a specific application area among networked robots, formation flying, bridge monitoring, and traffic monitoring. As an initial study to develop a reconfigurable receiver network, this paper deals with the design and implementation of the key elements of the reconfigurable receiver netowork; server, broadcaster, and client. In the designed receiver network, a sever receives and decodes measurements from a reference receiver installed at a known location, a broadcaster processes and transfers the messages from servers to clients and manages connections with servers and clients, a client receives the messages from the broadcaster and performs differential positioning. A real-time experiment result is demonstrated to validate the functionalities of each network element.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.2
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• pp.188-193
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• 2010

With GPS being the primary navigation system, Loran use is in steep decline. However, according to the final report of vulnerability assessment of the transportation infrastructure relying on the global positioning system prepared by the John A. Volpe National Transportation Systems Center, there are current attempts to enhance and re-popularize Loran as a GPS backup system through the characteristic of the ground based low frequency navigation system. To advance the Loran system such as Loran-C modernization and eLoran development, research is definitely needed in the field of Loran-C receiver signal processing as well as Loran-C signal design and the technology of a receiver. We have developed a set of Matlab tools, which implement a software Loran-C receiver that performs the receiver's position determination through the following procedure. The procedure consists of receiving the Loran-C signal, cycle selection, calculation of the TDOA and range, and receiver's position determination through the Least Square Method. We experiences the effect of an incorrect cycle selection and various error factors (ECD, ASF, sky wave, CRI, etc.) from the result of the Loran-C signal processing. It is apparent that researches which focus on the elimination and mitigation of various error factors need to be investigated on a software Loran-C receiver. These aspects will be explored in further work through the method such as PLL and Kalman filtering.