• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.93-97
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• 2007

In this paper a new clock generation scheme for TDM-CDM converter in the Gap Filler for satellite DMB systems has been proposed. The scheme uses the frame sync signal from the Ku band TDM receiver to lock the VCXO which provides the system clock for the TDM-CDM converter. The locking algorithm can be easily implemented in the FPGA, so that no separate circuitry is needed as in conventional PLL. With a stable OCXO, The scheme can be used to generate the reference clock to the local oscillator for RF parts.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.6
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• pp.712-717
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• 2014

The performance of npn SiGe HBT on thin film SOI is investigated at 32 nm technology node by applying body bias. An n-well is created underneath thin BOX to isolate the body biased SOI HBT from SOI CMOS. The results show that the HBT voltage gain and power gain can be programmed by applying body bias to the n-well. This HBT can be used in variable gain amplifiers that are widely used in the receiver chain of RF systems. The HBT is compatible with 32 nm FDSOI technology having 10 nm film thickness and 30 nm BOX thickness. As the breakdown voltage increases by applying the body bias, the SOI HBT with 3 V $V_{CE}$ has very high $f_tBV_{CEO}$ product (839 GHzV). The self heating performance of the proposed SOI HBT is studied. The high voltage gain and power gain (60 dB) of this HBT will be useful in designing analog/RF systems which cannot be achieved using 32 nm SOI CMOS (usually voltage gain is in the range of 10-20 dB).

• Journal of Magnetics
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• v.22 no.2
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• pp.238-243
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• 2017

In this research, we report the preliminary results of an insertional type parallel transmission (pTx) array that has 7-elements that are placed in the space above a patient table as a transmit (Tx) coil to give an RF transmission ($B_1{^+}$) field for the body object of a 3 Tesla (T) MRI system. In previous research, we have tried to compare the performances of different coil elements and array geometries for a pTx body image. Based on these results, we attempt to obtain a human image with the proposed pTx array. Through the simulation and experimental results, we introduce a possible structure of multi-channel Tx array and verify the utility of a multi-channel Tx body image using $B_1{^+}$ shimming. The insertional pTx array, combined with a receiver (Rx) array coil, provides an enhanced $B_1{^+}$ field homogeneity in a large ROI image as a result of $B_1{^+}$ shimming applied over the full body size object. Through this research, we hope to determine the usefulness of the proposed insertional type RF coil combination for 3 T body imaging.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.685-694
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• 2018

In this paper, we designed and fabricated the frequency mixer, which is the core parts of high frequency head in Ku-band tracking radar. To overcome the problem of single-ended and single-balanced resistive structure, we designed the fine-line structure with balanced mixer, to generate IF signal without distortion in L-band, after receiving the RF signal of the Ku-band. The prototype mixer showed a Noise Figure Max of 6.823dB, Gain of 4.1598~4.676dB and Band Pass of 61MHz in 5 Ku-band samples frequency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.3
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• pp.353-358
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• 1998

This paper presents development of a LNA operating at 1.71 ∼ 1.18 GHz used for a receiver of KOREA PCS base station and transponder. Using resistive decoupling circuits, a signal at low frequency is dissipated by a resistor. This design method increases the stability of the LNA and suitable for input stage matching. The LNA consists of low noise GaAs FET ATF-10136 and internally matched VNA-25. The LNA is fabricated with both the RF circuit and the self-bias circuits in aluminum housing. As a result, the characteristics of the LNA implemented here shows 30 dB in gain and 0.85 dB in noise figure.

• Journal of Digital Convergence
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• v.17 no.10
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• pp.243-249
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• 2019

In this paper, we have developed a device to reduce the standby power consumption that is unnecessarily consumed in unused electrical appliances. The Doppler sensor is used to automatically power off and power off the outlet depending on whether or not a person is present near the outlet. The Doppler sensor uses a coaxial cable trap to design a transmitting antenna and emits a 10 GHz band RF signal and receives a reflected wave signal whose wavelength is reflected from the target object to the receiver to detect an object and recognize human approach. It automatically cuts off and restores standby power to prevent unnecessary power consumption, saving energy and developing a standby power automatic shutdown and recovery device that can prevent the risk of large fires caused by leakage current.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.65-73
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• 2023

As one of the most vulnerable countries to floods, there should be an increased necessity for accurate and reliable flood forecasting in Indonesia. Therefore, a new prediction model using a machine learning algorithm is proposed to provide daily flood prediction in Indonesia. Data crawling was conducted to obtain daily rainfall, streamflow, land cover, and flood data from 2008 to 2021. The model was built using a Random Forest (RF) algorithm for classification to predict future floods by inputting three days of rainfall rate, forest ratio, and stream flow. The accuracy, specificity, precision, recall, and F1-score on the test dataset using the RF algorithm are approximately 94.93%, 68.24%, 94.34%, 99.97%, and 97.08%, respectively. Moreover, the AUC (Area Under the Curve) of the ROC (Receiver Operating Characteristics) curve results in 71%. The objective of this research is providing a model that predicts flood events accurately in Indonesian regions 3 months prior the day of flood. As a trial, we used the month of June 2022 and the model predicted the flood events accurately. The result of prediction is then published to the website as a warning system as a form of flood mitigation.

• International Journal of Computer Science & Network Security
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• v.24 no.3
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• pp.182-188
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• 2024

Hardware components are an integral part of Hardware Define Radio (HDR) for seamless operations and optimal performance. On the other hand, Software Define Radio (SDR) is a program that does not rely on any hardware components for its performance. Both of the latter radio programmers utilize modulation functions to make their core components from signal processing viewpoint. The following paper concentrates on SDR based modulation and their performance under different modulations. The bit error rate (BER) of modulations such as PSK, QAM, and PSAM were used as indicators to test channel quality estimation in planar Rayleigh fading. Though it is not commonly used for channel fading, the method of the adder determines the regionally segmented channel fading. Thus, the estimation error of the channel change substantially reduces the performance of the signal, hence, proving to be an effective option. Moreover, this paper also elaborates that BER is calculated as a function of the sample size (signal length) with an average of 20 decibels. Consequently, the size of the results for different modulation schemes has been explored. The analytical results through derivations have been verified through computer simulation. The results focused on parameters of amplitude estimation error for 1dB reduction in the average signal-to-noise ratio, while the combined amplitude deviation estimation error results are obtained for a 3.5 dB reduction

• Journal of The Korean Astronomical Society
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• v.46 no.6
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• pp.225-234
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• 2013

We develop a radio receiver system operating at ${\lambda}{\sim}1.3$ mm for the 6 m telescope of Seoul Radio Astronomy Observatory. It consists of a dual polarization receiver, a couple of IF processing units, two FFT spectrometers, and associated software. By adopting sideband-separating superconductor mixers with image band terminated to waveguide load at 4.2 K, we achieve $T_{RX}{\leq}100$ K and $T_{sys}$ less than 150 K at best weather condition over 210-250 GHz frequency range. The intermediate frequency signal of 3.5-4.5 GHz is down converted to 0-1 GHz and fed into the FFT spectrometers. The spectrometer covers 1 GHz bandwidth with a spectral resolution of 61 KHz. Test observations are conducted toward several radio sources to evaluate the performance of the system. Aperture and beam efficiencies measured by observing planets are found to be typically 44 ~ 59% and 47 ~ 61%, respectively over the RF band, which are consistent with those measured at 3 mm band previously.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1304-1310
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• 2010

This study is to design FMCW radar transceiver of K-band which is used to detect and track approaching high speed targets with low altitude. The transmitter needs high output power due to small RCS targets and wide beamwidth of transmit antenna. Multi-channel receivers are required to detect and track targets by interferometer method. Transmitter consists of high power amplifier, waveguide switch, and frequency up-converter. Receiver is composed of five channel receivers, up and down converters, X-band local oscillator and waveform generator. Before manufacturing it, the proposed architecture of transceiver is proved by modeling and simulation using several parameters. Then, it is manufactured by using industrial RF components. The performance parameters are measured through experiment. In the experiment, transmitting power and receiver gain were measured with 39.64 dBm and 29.1 dB, respectively. All other parameters in the specification were satisfied as well.