• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.91-95
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• 2008

This paper presents a direct-conversion I/Q up-mixer block, which supports $3{\sim}5$ GHz ultra-wideband(UWB) applications. It consists of a VI converter, a double-balanced mixer, a RF amplifier, and a differential-to-single signal converter. To achieve wideband characteristics over $3{\sim}5$ GHz frequency range, the double-balanced mixer adopts a shunt-peaking load. The proposed RF amplifier can suppress unwanted common-mode input signals with high linearity. The proposed direct-conversion I/Q up-mixer block is implemented using $0.18-{\mu}m$ CMOS technology. The measured results for three channels show a power gain of $-2{\sim}-9$ dB with a gain flatness of 1dB, a maximum output power level of $-7{\sim}-14.5$ dBm, and a output return loss of more than - 8.8 dB. The current consumption of the fabricated chip is 25.2 mA from a 1.8 V power supply.

• Progress in Superconductivity and Cryogenics
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• v.19 no.2
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• pp.14-18
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• 2017

This study presents three dimensional (3-D) seeding technique which is a modification of interior seeding. 3-D seeding is beneficial for shortening the processing period and enhancing the magnetic properties of REBCO bulk superconductors fabricated by melt growth. Oxygen channels were provided by using divided powder compacts instead of by using a rubber insert. Microstructure observations revealed that the grains grown from the seeds impinged each other and formed low angle grain boundaries of (001)/(001). It has been shown that the 3-D seeding technique reduces the volume fraction of a-c growth sector and thereby maximizes the area of a-b growth sector which attribute to the high magnetic characteristics of single grain REBCO bulk superconductors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.2
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• pp.102-114
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• 1987

In this paper, in order to develop the transmission system between the remote subscriber and the central office, the hardware and software implementation of a SMUX(Statistical Multiplexer)which can interleace eleven 16Kbps D-channels over a 64Kbps B-channel is obtained. As a result of this study, the high speed data transmission by the use of a dynamic buffer memory management algofithm for statistical multiplexing is realized. Especially a software architectur for interruption is proposed in order to improve performance of the transmission system more efficiently.

• Current Optics and Photonics
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• v.7 no.2
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• pp.166-175
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• 2023

We theoretically analyze and experimentally demonstrate a polarization-diversified four-channel optical demultiplexer (DeMUX) comprising a hybrid mode conversion-type polarization splitter rotator (PSR) and delayed Mach-Zehnder interferometer optical DeMUX for use in coarse wavelength division multiplexing (CWDM)-based optical interconnect applications. The Si wire-based device fabricated by a complementary metal-oxide semiconductor-compatible process exhibited nearly the same filter spectral response irrespective of the input polarization state under the PSR. The device had an extremely low insertion loss of <1.0 dB, polarization-dependent loss of <1.0 dB, and interchannel imbalance of <0.5 dB, suppressing unwanted wavelength and polarization crosstalk from neighboring channels of <-20 dB at each peak transmission channel grid.

• Journal of Acupuncture Research
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• v.18 no.2
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• pp.67-78
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• 2001

The aim of this study was to examine the effects of low frequency electroacupuncture(EA) at the $B_{62}$ (Shinmaek) $K_6$(Chohae) on vascular dementia in humans using nonlinear dynamics. Electroencephalogram(EEG) is a multi-scaled signal consisting of several components of time series with different dominant frequency ranges and different origins. Nonlinear measures of the EEG like the correlation dimension ($D_2$) and the first positive Lyapunov exponent ($L_1$) reflect the complexity of the EEG. In this study, $D_2$ was used as a measure of complexity. Sixteen channel EEG study was carried out in six subjects (5 females and 1 males; $age=83.83{\pm}7.19years$). We found that the baseline $D_2$ values of the EEG at F4 and F8 channels (P<0.01) were lowered than during the acupuncture treatment, indicating decreased complexity of the EEG. However, the comparison with that before and after the treatment shows no significant differences in all channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.223-231
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• 2011

It has been shown that the performance of multiple-input multiple-output (MIMO) spatial multiplexing systems is significantly degraded when spatial correlation exists between transmit and receive antenna pairs. In this paper, we investigate designs of a new statistical precoder for spatial multiplexing systems with maximum likelihood (ML) receiver which requires only correlation statistics at the transmitter. Two kinds of closed-form solution precoders based on rotation and power allocation are proposed by means of maximizing the minimum E tlidean distance of joint symbol constellations. In addition, we extend our results to linear receivers for correlated channels. We provide a method which yields the same profits from the proposed precoders based on a simple zero-forcing (ZF) receiver. The simulation shows that 2dB and 8dB gains are achieved for ML and ZF systems with two transmit antennas, respectively, compared to the conventional systems.

• Journal of the Korea Society of Computer and Information
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• v.18 no.11
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• pp.107-113
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• 2013

Mobile mobility and data reliability should be guaranteed as well as amounts of data services are essential in the era of smart media. In order to improve the reliability of high-speed data, strong channel coding and modulation techniques are required. In this paper, the structure of Turbo TCM decoder, applying high-order modulation techniques and the DPSAM method which improves performances in time-selective fading channels in the case of burst errors are suggested through the optimal decoding method and iteration decoding so as to improve bandwidth efficiency in Turbo Codes with excellent encoding gain. The proposed method in comparison with the existing method is that 3dB is superior in case that BER is $10^{-2}$ and the number of iterations is 3. In addition, the function is improved at approximately 6dB in case that BER is $10^{-3}$ and the number of iterations is 7. The proposed method requires additional bandwidth; however, the bandwidth loss can be overcome through Turbo TCM technology on the additional bit rate from the bandwidth loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.924-934
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• 2018

This paper describes the development and measurement results of C-band planar active phase array antenna for detecting and tracking radar(weapon-locating radar). The antenna is designed with 14 sub-arrays(12 main channels and 2 sidelobe blanking channels and approximately 3,000 elements of transmit-receive channel) to generate transmit and digital receive patterns. Using a near-field measurements facility, G/N, transmit patterns, and received patterns are measured. Receive patterns are implemented with digital beamforming by signal processing. The measurement results demonstrate that antenna design specifications were fulfilled.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.25-25
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• 2003

Atrial myocytes have two functionally separate $Ca^{2+}$ release sites: those in peripheral sarcoplasmic reticulum (SR) adjacent to the $Ca^{2+}$ channels of surface membrane and those in central SR not associated with $Ca^{2+}$ channels. Study on the spatio-temporal properties of focal $Ca^{2+}$ releases (“sparks”) occurring spontaneously in central and peripheral sites of voltage-clamped rat atrial myocytes, using rapid two-dimensional (2-D) confocal $Ca^{2+}$ imaging revealed that peripheral and central sparks were similar in size and release time (~300,000 $Ca^{2+}$ ions for=12 ms), but significantly larger and longer than ventricular sparks. Both sites were resistant to Cd$^{2+}$ and inhibited by ryanodine. Peripheral sparks were brighter and flattened against surface membrane, had ~5-fold higher frequency, ~2 times faster diffusion coefficient, and dissipated abruptly. Central sparks, in contrast, occurred less frequently, were elongated along the cellular longitudinal axis, and dissipated slowly. Compound sparks (composed of 2-5 unitary focal releases) aligned longitudinally, occurred more frequently at the center.at the center.

• Korean Journal of Biological Psychiatry
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• v.21 no.4
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• pp.151-160
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• 2014

Objectives Prenatal testosterone is known to influence both cerebral laterality and 2nd to 4th digit ratio (2D : 4D). Epigenetic changes are thought to play some role in it. We studied sex-related differences between 2D : 4D and cerebral laterality in patients with schizophrenia and controls to examine the effects of prenatal testosterone in the development of schizophrenia. Methods Forty one men (18 schizophrenic patients and 23 controls) and 40 women (17 schizophrenic patients and 23 controls) were recruited from one psychiatric hospital in Korea. The 2D : 4D and electroencephalographic (EEG) coherence in 19 channels (66 pairs of interhemispheric coherence and 54 pairs of intrahemispheric coherence) were measured. The sex-related statistical analyses between 2D : 4D and EEG coherence in controls and patients with schizophrenia were performed using multiple regression. Results In male patients, the relationship between 2D : 4D and right intrahemispheric EEG coherence showed mainly positive correlation in delta and theta frequency bands, while it showed negative correlation in male controls. In female patients, the relationship between 2D : 4D and interhemispheric EEG coherence showed stronger positive correlation in alpha and beta frequency bands, while it showed weaker positive correlation in female controls. Conclusions Low prenatal testosterone may play certain roles in altered correlation between 2D : 4D and cerebral laterality in schizophrenia and the development of schizophrenia by epigenetic mechanism.