• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1292-1299
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• 2014

Weather radar systems can provide weather information of the ground, sea, and air in extensive spatial coverage in near real time. However, it becomes problematic when ground clutter signal exists around precipitation because strong signals of ground can cause a false precipitation report. A large percentage of land coverage of Korea consists of mountainous regions where ground clutter needs to be mitigated for more accurate prediction. Thus, it is considered necessary to introduce a new suitable ground clutter removal technique specifically adequate for Korea. In this paper, the C-Map(Clutter Map) method using raw radar signals is proposed for removing ground clutter using a terrain-adaptive clutter map. A clutter map is generated using raw radar signals(I/Q) of clear days, then it is subtracted from received radar signals in frequency domain. The proposed method is applied to the radar data acquired from Sobaeksan rain radar and the result shows that the clutter rejection ratio is about 91.17 %.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1156-1164
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• 1999

In this paper, we have studied the 8 YSB (8 Vestigial Side Band) method which is decided as the standard of modulators for next generation digital TV System. In developing digital TV System, one of the difficult problems is how digital signal can be transmitted to the receiver without any phase distortion. But, phase error is liable to occur by imperfect design, circumstance variation and device degradation. These characteristics result in distortion of 1,0 signal of modulator and interference in adjacent channels. In particular, the interference in modulator of a high power amplifier result in serious problems in adjacent channels. Here we analyzed problems of phase error which are occurred when 8 levels digital signals are modulated to If signal. And we suggested phase error compensation algorithm and discussed the results for adaptation of the algorithm

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.3
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• pp.1-8
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• 2000

This paper presents a simulation model of the Quadrature detector to demodulate FSK signal, which is widely used in wireless paging system for its simple hardware implementation and economics of It fabrication. Quadrature detecter has nonlinear phase characteristic for changes linear changes of input signal frequency. So until now Quadrature detector system analysis remained a difficult problem and performance analysis has not been carried out adequately On these backgrounds, this paper presents the FSK signal demodulation process using Quadrature detector and optimal performance derived from digital simulation technique. First, PSN(Phase Shift Network) which is composed of analog RLC tank circuit is transformed into its equivalent digital transfer function using First-order-hold theorem. Though the demodulated outputs of the Quadrature detector for 4FSK are 4-level signals, only 2 comparators are used and it is shown that optimal performance can be obtained by choosing operation parameter Q value and threshold level decision which are proposed herein.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1339-1349
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• 2008

In this paper, a nonlinear relationship between an input complex envelope and an output complex envelope of m-th harmonic zone is theoretically analyzed, and AM/$AM_m$ and AM/$PM_m$ are defined. A scheme to extract these characteristics from measured in-phase and quadrature-phase data is suggested. The proposed analysis is verified with a fundamental-fundamental and fundamental-third harmonic measurements for a InGaP power amplifier(PA). Based on the harmonic-band nonlinear analysis and extraction scheme, a new technique to send a signal in m-th harmonic band with a harmonic signal Linearization Digital Predistortion(DPD) scheme is presented. A numerical analysis and a Look-Up Table(LUT) based DPD algorithms to linearize output signal on m-th harmonic zone are developed. For a 16- and a 64-QAM input signals, a DPD for third harmonic signal linearization is implemented, and output spectrum and signal constellation are measured. The wholly distorted signals are linearized, and thus the measured Error Vector Magnitudes (EVM) are 6.4 % and 6.5 % respectively. The results show that a proposed scheme linearizes a nonlinearly distorted harmonic band signals. The proposed nonlinear analysis and predistortion scheme can be applied to multiband transmitter in next generation software defined radio(SDR)/cognitive radio(CR) wireless system.

• Investigative Magnetic Resonance Imaging
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• v.22 no.1
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• pp.65-70
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• 2018

The objective of this study was to describe a radiofrequency (RF) coil design for in vivo sodium magnetic resonance imaging (MRI) for use in small animals. Accumulating evidence has indicated the importance and potential of sodium imaging with improved magnet strength (> 7T), faster gradient, better hardware, multi-nucleus imaging methods, and optimal coil design for patient and animal studies. Thus, we developed a saddle-shaped sodium volume coil with a diameter/length of 30/30 mm. To evaluate the efficiency of this coil, bench-level measurement was performed. Unloaded Q value, loaded Q value, and ratio of these two values were estimated to be 352.8, 211.18, and 1.67, respectively. Thereafter, in vivo acquisition of sodium images was performed using normal mice (12 weeks old; n = 5) with a two-dimensional gradient echo sequence and minimized echo time to increase spatial resolution of images. Sodium signal-to-noise ratio in mouse kidneys (renal cortex, medulla, and pelvis) was measured. We successfully acquired sodium MR images of the mouse kidney with high spatial resolution (approximately 0.625 mm) through a combination of sodium-proton coils.

• Journal of electromagnetic engineering and science
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• v.4 no.4
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• pp.143-149
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• 2004

This paper describes characteristics of the single-balanced low IF resistive FET mixer for the digital beam forming(DBF) receiver. This DBF receiver based on the direct conversion method is designed with Low IF I and Q channel. A radio frequency(RF), a local oscillator(LO) and an intermediate frequency(IF) considered in this research are 1950 MHz, 1940 MHz and 10 MHz, respectively. Super low noise HJ FET of NE3210S01 is considered in design. The measured results of the proposed mixer are observed IF output power of -22.8 dBm without spurious signal at 10 MHz, conversion loss of -12.8 dB, isolation characteristics of -20 dB below, 1 dB gain compression point(PldB) of -3.9 dBm, input third order intercept point(IIP3) of 20 dBm, output third order intercept point(OIP3) of 4 dBm and dynamic range of 30 dBm. The proposed mixer has 1.0 dB higher IIP3 than previously published single-balanced resistive and GaAs FET mixers, and has 3.0 dB higher IIP3 and 4.3 dB higher PldB than CMOS mixers. This mixer was fabricated on 0.7874 mm thick microstrip $substrate(\varepsilon_r=2.5)$ and the total size is $123.1\;mm\times107.6\;mm$.

• Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.10.1-10.7
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• 2017

Small GTPases are well known as one of the signal transduction factors of immune systems. The ADP-ribosylation factors (ARFs) can be classified into three groups based on the peptide sequence, protein molecular weight, gene structure, and phylogenetic analysis. ARF1 recruits coat proteins to the Golgi membranes when it is bound to GTP. The class I duplicated ARF gene was cloned and characterized from the olive flounder (Paralichthys olivaceus) for this study. PoARF1b contains the GTP-binding motif and the switch 1 and 2 regions. PoARF1b and PoARF1b mutants were transfected into a Hirame natural embryo cell to determine the distribution of its GDP/GTP-bound state; consequently, it was confirmed that PoARF1b associates with the Golgi body when it is in a GTP-binding form. The results of the qPCR-described PoARF1b were expressed for all of the P. olivaceus tissues. The authors plan to study the gene expression patterns of PoARF1b in terms of immunity challenges.

• Journal of Communications and Networks
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• v.13 no.4
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• pp.327-338
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• 2011

With the incitation to reduce power consumption and the aggressive reuse of spectral resources, there is an inevitable trend towards the deployment of small-cell networks by decomposing a traditional single-tier network into a multi-tier network with very high throughput per network area. However, this cell size reduction increases the complexity of network operation and the severity of cross-tier interference. In this paper, we consider a downlink two-tier network comprising of a multiple-antenna macrocell base station and a single femtocell access point, each serving multiples users with a single antenna. In this scenario, we treat the following beamforming optimization problems: i) Total transmit power minimization problem; ii) mean-square error balancing problem; and iii) interference power minimization problem. In the presence of perfect channel state information (CSI), we formulate the optimization algorithms in a centralized manner and determine the optimal beamformers using standard convex optimization techniques. In addition, we propose semi-decentralized algorithms to overcome the drawback of centralized design by introducing the signal-to-leakage plus noise ratio criteria. Taking into account imperfect CSI for both centralized and semi-decentralized approaches, we also propose robust algorithms tailored by the worst-case design to mitigate the effect of channel uncertainty. Finally, numerical results are presented to validate our proposed algorithms.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.1
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• pp.28-35
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• 2001

In this paper, an electronic starter and controller are develor:ed for blinking and color variation oI:'||'&'||'pound;fations of fluorescent ]arrps, which would be suitElble for use in an advertising panel. The deve1oporl electrornc starters enable single-pulse ignition for fluorescent lamps of 2O-4Q[W] according to the start signal of controller, and the lamp life is e;.qxccted to go beyond 3,OCO hours with blinking o]:ffations for minimum 0.2[s]. Also, the controller based on a micro-controller can handle up to 128 fluorescent lanlpS and have ten modes of blinking pattems and 7-color variation mxles.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.113-118
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• 2012

In this paper, we discuss the design of the Digital Down Converters for the IEEE 802.11 wireless LAN receiver, which can be used for the customized receiver. The customized receiver can be used for special puropsed services which cannot be realized using the general custom chip. In the OFDM receiver, DDC receives the up sampled Inphase/Quadrature signal from the AD converter and process down sampling and filtering procedures using the Cascaded Intergrator Filter and FIR filters. We discuss the structure and design methodology of DDC's and analyze the simulation results.