• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9C
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• pp.810-819
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• 2007

The I/Q unbalance which is generated by non-ideal components such as a $90^{\circ}$ phase shifter and I/Q filters is an inevitable physical phenomenon and leads to performance degradation when we implement a coherent two-dimensional (2-D) modulation/demodulation system. This paper provides an exact and general expression for the SEP(symbol error probability) of DVB-S2 system with I/Q phase and amplitude unbalance over AWGN channel. Coordinate rotation and shift techniques used to redefine a received signal are key mathematical tools. In conclusion, the derived result is expressed as a linear combination of the 2-D Gaussian Q-functions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.167-170
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• 2000

The structural changes and the dielectric properties of $(Ba_{1-x}Ca_x)(Mg_{1/3}Ta_{2/3})O_3$ (x=0, 0.2, 0.4, 0.6, 0.8, 1) were investigated. The densities of samples were gradually decreased with increasing x, (BMT=7.69, CMT=5.25 $g/cm^3$). The crystal structure of BMT was a untiltied perovskite structure, however BCMT showed antiphase tilting and antiphase-inphase tilting structure. The dielectric constant($\varepsilon_r$) of the highest value was 33 at x=0.2 (BMT=24, CMT=17). The maximum quality factor was 27,500GHz in BMT. The quality factor· of BCMT was decreased to x<0.2 (5,000GHz), and was gradually increased to x>0.2. The temperature coefficients of dielectric constant was positive at x<0.8, and negative in CMT.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.488-491
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• 2006

In this paper proposed method of maximum power point tracking using boost converter for a connected single phase inverter with photovoltaic system. The maximum power point tracking control is based on generated circuit control MOSFET switch of boost converter and single phase inverter uses predicted current control to control four IGBT's switch in full bridge. The predicted current control provide current with sinusoidal wave shape and inphase with voltage. The generation control circuit allows each photovoltaic module to operate independently at peak capacity, simply by detecting of the output power of the system. Furthermore, the generation control circuit attenuates low-frequency ripple voltage, which is caused by the full-bridge inverter, across the photovoltaic modules. Consequently, the output power of system is increased due to the increase in average power generated by the photovoltaic modules. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.502-513
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• 2004

This paper proposes a symbol synchronization method in the IEEE 802.11a wireless OPDM system, which uses only signs of the in-phase and the quadrature signals in the short preamble. The short preamble is sampled with 2 tines of Nyquist sampling rate and both of the autocorrelation and the cross-relation are used in the proposed method. This method has some advantages that the ACG (Automatic Gain Control) can be processed concurrently during the short preamble and its implementation is not much complicated. The proposed symbol synchronization method is verified through simulations on frequency offset, multi-path and white Gaussian noise.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.434-441
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• 2005

For LDPC decoding, received symbols are splitted bit by bit based using the received in-phase and quadrature components. The method of bit-splitting is affected on decoding performance because its method depend on distance over symbol constellation. Therefore this paper propose the bit split method using the sector information with sacrifice a little performance loss compared to Euclidean distance method. Futhermore DVB-S2 specification supports BC(Backward Compactible) mode which using the hierarchical modulation method, this paper also analyze the decoding performance according to deviation angle of 8PSK constellation for various LDPC coding rates.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.66-73
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• 2010

This paper proposes the frequency multiplier using diplexer based on CRLH transmission line with dualband characteristic. The diplexer is separated the output signals of harmonic generator, which is generated the harmonic signals using nonlinear device. The diplexer consists of the inphase power divider, 0o/90o phase controller and dual-band quadrature hybrid coupler. This send out the selecting output signals of the harmonic signals and suppresses out of signals. To validate a function of multiplier, the harmonic generator and diplexer with 2 GHz and 3 GHz operating frequency range is implemented. As a result, the proposed frequency multiplier is operated normally.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.478-484
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• 2000

The structural changes and the microwave dielectric properties of $Ba_{1-x}$/A$_{x}$/(Mg$_{1}$3//Nb$_{2}$3/)O$_3$(A=Sr, Ca=x0, 0.2, 0.4, 0.6, 0.8, 1.0) were investigated. The densities of samples are gradually decreased with increasing x(BMN=6.1, SMN=5.22 and CMN=4.26 g/m$^3$)The crystal structure of BMN was untilting of oxygen octahedral. The structural changes of BSMN showed the antiphase tilting at x>0.4, and those of BCMN showed the antiphase tilting at 0.20.8. The variation of dielectric constant with Sr was small(BMN=32, SMN=30) However the variation with Ca was large the highest value was 42 at Ca=0.2(CMN=25) The maximum quality factor was 68,000 GHz at Sr=0.2 and the minimum quality factor was 3,000 GHz at Ca=0.2 (BMN=35,000, SMN=20,000 and CMN=23,000 GHz) The temperature coefficients of resonant frequency of BSMN were about 2 times larger than those of BCMN in all composition.ion.

• Investigative Magnetic Resonance Imaging
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• v.1 no.1
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• pp.142-147
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• 1997

Purpose: To compare the effectiveness of the in-phase (IP) sequence and the opposed-phase (Op) sequence in the detection of focal hepatic lesions in the single breath-hold hepatic MR imaging with fast gradient T1-weighted pulse sequences. Materials and Methods: IP and OP T1-weighted breath-hold imaging was performed using fast gradient echo sequences in 45 patients referred for known focal hepatic lesions, in which 78 lesions were detected. Three blind readers independently reviewed the images for lesion detectability. The signal-to-noise ratio (SNR) of the liver, the lesion-to-liver contrast-to-noise ratio (CNR) and the liver-to-spleen CNR were also compared. A consensus was reached by three readers to determine which sequence is better in image quality. Results: On OP images, 61(78%), 61(78%), and 63(89%) lesions were correctly identified for reader 1, 2 and 3, respectively. On IP images, 66(85%), 65(83%), and 65(93%) lesions were detected for each reader, respectively. When two image sets were combined, 71(91 %), 69(88 %), and 76(97%) lesions respectively were detected for each reader. In cases of hepatocellular carcinoma, liver-to-Iesion CNR was greater on the OP images(p (0.05), but in other lesions significant difference was not demonstrated. Liver-to-spleen CNR was higher on OP images(p ( 0.1), but the SNR of the liver was higher on the IP images. Conclusion: Use of both IP and OP imaging can be helpful to avoid erroneous missing of some focal hepatic lesions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.418-425
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• 2014

This paper presents a Ku-Band Doppler Radar System to measure respiration and heart rate. It was measured by using simultaneous radar and ECG(Electrocardiogram). Arctangent demodulation without dc offset compensation can be applied to transmitted I/Q(In-phase & Quadrature-phase) signal in order to improve the RMSE(Root Mean Square Error) about 50 %. The power leaked to receiving antenna from the transmitting antenna is always generated because of continuously opening the transceiver of CW(Continuous Wave) Doppler radar. As the output power increase, leakage power has an effect on the SNR(Signal-to-Noise Ratio) of the system. Therefore, in this paper, leakage cancellation technique that adds the signal having the opposite phase of the leakage power to the leakage power was implemented in order to minimize the decline of receiver sensitivity. By applying the leakage cancellation techniques described above, it is possible to measure the heart rate and respiration of the human at a distance of up to 35 m. the heart rate of the measured data at a distance of 35 m accords with the heart rate extracted from the ECG data.

• Journal of the Korean Geographical Society
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• v.47 no.2
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• pp.159-178
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• 2012

Since the suggestions on the paleo-glacial landforms in and around the northern high mountains of Korean Peninsula by some western and Japanese scientists in the early 1900s, the likelihood of the glacier existence in the Baekdusan over the Quaternary glacial period has been had in common among most of the Korean geomorphologists. In the other meaning, some have cast doubt on the likelihood the paleo-glacier in the Baekdusan because there has been no unequivocal evidences for the glacier such as striation, moraines, except morphologic characteristic landforms possibly related to glacier. Here we show some evidences for the existence of the glacier in the Baekdusan and their cosmogenic $^{36}Cl$ exposure ages over the late Quaternary and would put forward a model on the Quaternary landscape evolution of the Baekdusan, with a focus on the relationship of 1000 AD explosive eruption and the glacial landforms. The exposure ages constrained by cosmogenic $^{36}Cl$ abundances of the col surface of the western slope located below the glacier yield 46~26 ka, which is inphase with the last glacial period. Given all the evidences above, we can draw a conclusion that the glacier existed on the Baekdusan over the late Quaternary and the style of glaciation changed from extensive ice cap through valley glacier to restricted cirque.