• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.9-15
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• 1994

In this paper, the linearized power amplifier using digital adaptive predistorter is implemented in order to restrict spectral spreading and adjacent channel interference. The linearized systems is composed of a DSP56001 processor that executes predistortion in baseband. 90.deg. phase shifter, power splitter/combiner, quadrature modulator/demodulator of 360MHz band, and nonlinear amplifier. A ${\pi}$/4-shift QPSK is used to modulate digital random signals. As the quantized power of baseband signal and the output of amplifier are fed to the predistorter, and predistorting values are calculated using an adaptive algorithm. In the experiment, a peak to sidelobe ratio of the linearized amplifier is improved up to 15dB in comparison with conventional nonlinear amplifier, which means that the distortion of transmitted signal is decreased and adjacent channel interference was reduced.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.125-131
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• 1996

In this paper, we introduced the BQBPH method for making the grating of high efficiency which was improtant in implementing optical PS. The pattern of graing was obtianed by computer simulations using iterative method, and the diffraction efficeincy of designed grating was about 67% through BPM simulation. The grating was fabricated by laser beam writer, and the diffraction efficiency BPM simulation. The grating was fabricated by laser beam writer, and the diffraction efficiency was 47%. We implemented the optical PS with the grating and showed that optical experimental output patterns were good agreement with PS output patterns and first order was main diffraction order.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.165-171
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• 1996

A noncoherent full-digital PN(pseudo noise) code acquisition/tracking loop has been presetned and implemented in FPGA for the CDMA band-limited direct-sequence spread-spectrum (DS-SS) signals. It employs a simple decimator to control of local PN code phase to lower the hardware cost, and a second order loop to enable the more accurate tracking. The proposed acquisition/tracking loop has been designed in RTL-level VHDL, synthesized into logic gates using the design analyzer of synopsys software, implemented in an ALTERA FPGA chip, and tested. The number of logic gates used in the implemented FPGA chip is around 7000. The functionality has been verified using a PC interface circuitry and a logic analyzer.

• ETRI Journal
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• v.20 no.1
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• pp.16-27
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• 1998

In this paper, we consider the acquisition performance of an IS-95 reverse link access channel slot as a function of system design parameters such as postdetection integration length and the number of access channel message block repetitons. The uncertainty region of the reverse link spreading codes compared to that of forward link is very small, since the uncertainty region of the reverse link is determined by a cell radius. Thus, the parallel acquisiton technique in the reverse link is more efficient than a serial acquisition technique in terms of implementation and of acquisition time. The parallel acquisition is achieved by a bank of N parallel I/Q noncoherent correlator are analyzed for band-limited noise and the Rayleigh fast fading channel. The detection probability is derived for multiple correct code-phase offsets and multipath fading. The probability of no message error is derived when rake combining, access channel message block combining, and Viterbi decoding are applied. Numerical results provide the acquisition performance for system design parameters such as postdetection integration length and number of access channel message block repetitions in case of a random access on a mobile station.

• Spatial Information Research
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• v.9 no.1
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• pp.155-169
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• 2001

Although the strategies and experiences of GIS leading countries are considered for the implementation of NGIS-Development in Korea, the western european nations cases are not analysed. Based on this study focused on German approaches to establish and implement the construction of national geospatial data framework. The goals, construction strategies and contexts of german national framework data, it called authoritative topographic-cartographic information system(ATKIS) in germany, are presented in detail. As a result, some lessons are suggested that can be learned by german approaches. Because we are now standing on the phase of "A Second Master Plan for National Geographic Information System", the german approach can be very for the development of the national framework database in Korea.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.1
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• pp.1-14
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• 2018

The Global Positioning System (GPS) provides more accurate positioning estimation performance by processing L1 and L2 signals simultaneously through dual frequency signal processing technology at the L-band rather than using only L1 signal. However, if anti-spoofing (AS) mode is run at the GPS, the precision (P) code in L2 signal is encrypted to Y code (or P(Y) code). Thus, dual frequency signal processing can be done only when the effect of P(Y) code is eliminated through the L2 signal processing technology. To do this, a codeless technique or semi-codeless technique that can acquire phase measurement information of L2 signal without information about W code should be employed. In this regard, this paper implements L2 signal processing technology where two typical codeless techniques and four typical semi-codeless techniques of previous studies are applied and compares their performances to discuss the optimal technique selection according to implementation environments and constraints.

• Journal of computational fluids engineering
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• v.7 no.4
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• pp.28-34
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• 2002

A general purpose program for computing 3-D flows has been extended for two-phase flows with topologically complex interfaces. The 3-D interfaces are tracked by employing a coupled level set and volume-of-fluid (CLSVOF) method which not only can calculate an interfacial curvature accurately but also can achieve mass conservation well. The program has been tested through the computations of bubbles rising in a liquid. The numerical results are found to compare well with the results reported in the literature.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.16-20
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• 2008

This paper presents the construction of micro tool clamping device using a Ni-Ti shape memory alloy(SMA) ring. Clamping force of the device is produced by elastic force of the SMA reverted to its original shape in normal temperature. Phase transformation of the SMA was realized by temperature control using a peltier element. Prototype of the SMA tool clamping device was fabricated and examined its clamping force and clamping/unclamping operation.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.1049-1052
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• 1999

We present a use. interface(UI) simulator for developing a mobile phone. This simulator consists of 3 major modules: Graphic Tool Editor, User Interface Software(UI), and Network Command Processor(NCP). The Graphic Tool Editor can design a virtual mobile terminal. The NCP sends a command to the phone and then receives its status from the phone after completion of the command. We can add or modify lots of features easily to the phone using the UI module. These modules can interact each other by sharing the common area in the memory. By doing so, these modules can exchange their status and data to operate in real-time. We have designed and tested a virtual prototyping phone for the LGP 3200 manufactured by LGIC by using the simulator. Through a series of experiment, we have believed that our virtual prototyping interactive simulator can do shorten its development and testing cycle by applying it in the early design phase.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.58-67
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• 1995

In this paper, we present a new HPEJTC system which is capable of real-time multi-target recognition and tracking with better discrimination by extracting the phase signal of reference function from the JTPS of the conventional optical JTC retaining the amplitude signal of the input function. In order to test the correlation discrimination performance of the HPEJTC system, some experiments are carried out on the scenarios susceptible to the false alarms and missing in which many similar targets are periodically loacted. And, the proposed HPEJTC is analyzed to be the real function version of the POF and finally the possibility of the real-time implementation of the POF is suggested, because it can be implemented by using spatial light modulator, CCD detector and some other optical components.