• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.492-501
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• 2013

In this paper, a multi polarization reconfigurable microstrip antenna that can be used selectively for four polarizations(vertical polarization, horizontal polarization, right hand circular polarization, left hand circular polarization) at the S-band is presented. The proposed antenna consists of four PIN diodes and a microstrip patch with a cross slot and a circular slot and is fed by utiliting electromagnetic coupling between the microstrip patch and the feed line. The proposed antenna has a DC bias network to supply DC voltage to each PIN diode and the polarization can be determined by controlling the ON /OFF states of four PIN diodes. The fabricated antenna has a VSWR below 2 in the vertical polarization(3.17~3.21 GHz), the horizontal polarization(3.16~3.20 GHz), the left hand circular polarization (3.08~3.19 GHz), and the right hand circular polarization(3.10~3.2 GHz) frequency bands. The designed antenna has the cross polarization level higher than 20 dB, a gain over 5 dBi for the linear polarization states, and 3 dB axial ratio bandwidth wider than 50 MHz in the circular polarization states.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.42-49
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• 2018

In this paper, a dual-band microstrip-fed monopole antenna with a DGS(defected ground structure) for WLAN(wireless local area network) applications is presented. The antenna consists of a monopole and a defected ground, which were etched on both sides of the FR-4 substrate. The defected ground structure was used to obtain the dual band, while the step-by-step reduction in the monopole width was used to improve the impedance matching of the antenna. The antenna has an overall compact size of $44{\times}51{\times}1.6mm^3$, which was optimized by varying the size of the monopole and the ground plane such that it may resonate at the 2.4 GHz and 5 GHz bands of the WLAN. The measurement results showed that the antenna operates in the frequency band of 210 MHz(2.29~2.50 GHz) and 900 MHz(5.05~5.95 GHz) for a VSWR under 2, and showed omnidirectional radiation pattern at all desired frequencies.

• Korean Journal of Human Ecology
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• v.9 no.1
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• pp.137-152
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• 2000

The purpose of this study was to investigate the disposition of adolescents in their ornament wearing pattern associate with their life style and clothing behavior. The subject of this study consists of 345 middle and high school girls living in Chung-Nam Province and Taejon Metropolitan City. SPSS/PC+ program was utilized to calculated frequency(N), mean value(M) and standard deviation(SD) for statistical analysis. Differences among the populations were examined through f test, ANOVA. The results of this study reveals that the ornaments wearing patterns are significantly different according to their life style and clothing behavior as follows: 1. Correlation between the wear of ornaments and the life style: School girls who pursue the modernistic life style prefer the fashionable ornaments (e.g. sunglasses) and they are always in contact with the latest information. On the contrary, school girls who pursue the practical life style emphasize on the practical use when they purchase the ornaments, e.g. umbrella. School girls having romantic or passive nature have a preference for the brand name and brand image of the ornaments and they in general would like to buy ornaments such as the bracelets. 2. Correlation between the wear of ornaments and the clothing behavior: School girls having sympathetic nature and being deeply interested in clothing put a stress on the latest fashion of the ornaments. They usually want to buy fashionable ornaments such as the cellular phone, beeper and sunglasses. Subjects who estimate themselves by their garments are sensitive to the price of the ornaments while aesthetes emphasize the brand image of the ornaments. Chaste school girls put their emphasis on the quality of the ornaments and they most want to have functional hair bands. Following suggestions can be made based on the discussions above: It is necessary for us to have correct understanding about the correlation between the ornaments and clothing of school girls in order to lead them to have appropriate clothing behavior. Furthermore, it is required to construct a bridge linking a course of study to rational habits guidance which will provide us more appropriate tools for clothing behavior guidance.

• Biomedical Science Letters
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• v.6 no.3
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• pp.201-208
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• 2000

The vancomycin, one of the family of glycopeptide antibiotics, inhibits the synthesis of bacterial cell wall peptidoglycan and has been widely used against gram-positive bacterial infections, especially for a treatment of methicillin resistant S. aureus infection. However, clinical isolate which was intermediately resistant to vancomycin (Mu50: MIC 8 $\mu\textrm{g}$/ml) was isolated in recent years. In this study we performed vancomycin susceptibility test with the increment method and population analysis with clinical isolates S. aureus. Also we did several kinds of tests with three selected isolates (s129: MIC 7 $\mu\textrm{g}$/ml, s134: MIC 7 $\mu\textrm{g}$/ml, s135: MIC 8 $\mu\textrm{g}$/ml) to find out possible mechanism of vancomycin resistance. As a result, the prevalence of vancomycin resistant S. aureus isolates among S. aureus strains resistant to methicillin was 23.3% (25/107). The vancomycin resistances of isolated strains of S. aureus were between those of Mu5O and Mu3 strains. By PCR analysis, none of the isolates with decreased vancomycin susceptibility contained known vancomycin resistant genes such as vanA, vanB, vanC1, vanC2, and vanH. Major bands of 81 kDa, 58 kDa, 33 kDa, 28 kDa were demonstrable in whole cell lysates by SDS-PAGE from all three isolates as well as reference strains. And especially,45 kDa protein was overproduced in Mu50 strains. Among them increased production of NAD$^{+}$-linked-$_{D}$-lactate dehydrogenase (dnLDH) were detected from one clinical strain (s135) and Mu5O strain. From these data, we suggest that the mechanism of vancomycin resistance in these isolates are distinct from that in enterococci.

• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.595-603
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• 2016

In the Republic of Korea, the LTE-based public safety (PS-LTE) network is being built for the 700 MHz frequency band. However, the same bands are also assigned to the LTE-based high-speed railway (LTE-R) network. Therefore, it is essential to utilize the co-channel interference management schemes for the coexistence of two LTE networks in order to increase the system throughput and to reduce the user outage probability. In this paper, we focus on the downlink (DL) system for the coexistence of PS-LTE and LTE-R networks by considering non radio access network (RAN) sharing and LTE-R RAN sharing by PS-LTE users (UEs) to analyze the UE throughput. Moreover, we also utilize the cooperative communications schemes, such as coordinated multipoint (CoMP) for the coexistence of PS-LTE and LTE-R networks in order to reduce the UE outage probability. We categorize the coexistence of PS-LTE and LTE-R networks into four different scenarios, and evaluate the performance of each scenario by the important performance indexes, such as UE average throughput and UE outage probability.

• Journal of KIISE:Software and Applications
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• v.29 no.11
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• pp.837-850
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• 2002

In this paper, we propose an EEG-based response time prediction method during a yes/no cognitive decision task. In the experimental task, a subject goes through responding of visual stimulus, understanding the given problem, controlling hand motions, and hitting a key. Considering the subject's varying brain activities, we model subjects' mental states with defining CT (cut time), ST (selection time), and RP (repeated period). Based on the assumption between ST and RT in the mental model, we predict subjects' response time by detection of selection time. To recognize the subjects' selection time ST, we extract 3 types of feature from the filtered brain waves at frequency bands of $\alpha$, $\beta$, ${\gamma}$ waves in 4 electrode pairs combined by spatial relationships. From the extracted features, we construct specific rules for each subject and meta rules including common factors in all subjects. Applying the ST detection rules to 8 subjects gives 83% success rates and also shows that the subjects will hit a key in 0.73 seconds after ST detected. To validate the detection rules and parameters, we test the rules for 2 subjects among 8 and discuss about the experimental results. We expect that the proposed detection method can be a basic technology for brain-computer-interface by combining with left/right hand movement or yes/no discrimination methods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.327-332
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• 2017

As Internet of Things (IoT) technology advances, there is a growing demand for location-based services (LBSs) to identify users' mobility and identity. The initial LBS system was mainly used to measure position information by measuring the phase of a signal transmitted from a global positioning system (GPS) satellite or by measuring distance to a satellite by tracking the code of a carrier signal. However, the use of GPS satellites is ineffective, because it is difficult to receive satellite signals indoors. Therefore, research on wireless communications systems like ultra-wide band (UWB), radio frequency identification (RFID), and ZigBee are being actively pursued for location recognition technology that can be utilized in an indoor environment. In this paper, we propose an LBS system that includes the 2.45GHz band for chirp spread spectrum (CSS), and the 3.1-10.6GHz band and the 250-750MHz bands for UWB using the IEEE 802.15.4a standard for low power-based location recognition. As a result, we confirmed that the 2.45GHz Industrial, Scientific and Medical (ISM) band RF transceiver and the ranging function can be realized in the hardware and has 0dBm output power.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.10 s.352
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• pp.111-117
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• 2006

Reconfigurable CMOS low-noise amplifier (LAN) has been developed for multi-mode/multi-band wireless receiver. By employing common-gate input stage, the performance can be optimized for multiple operation bands by simply controlling the output load impedance. Although the conventional common-gate LAN has larger than 3dB noise figure (NF), the newly developed negative feedback scheme enables the common-gate input LNA to have less than 2dB NF. To have optimum linearity performance of wireless receiver, the gain of the LNA can be controlled. The LNA implemented in a 0.13mm CMOS technology shows $19{\sim}20dB$ voltage gain, $1.7{\sim}2.0dB$ NF, -2dBm iIP3 at $1.8{\sim}2.5GHz$ frequency range. The LNA dissipates 7mW from a 1.2V supply voltage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.68-78
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• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.212-224
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• 1998

There are two major factors of degrading the performance in the forward link of DS/CDMA systems. One is the multiple access interference (MAI) caused by using the same frequency bands simultaneously and the other is the multipath lading due to multipath propagation. PN codes which have minimum cross correlation properties among spread spectrum codes are necessary to reduce the MAI. In the conventional IS-95A system, the PN sequence has the period of $2^{15}$ and is of the length of 64 chips for spreading each data. In this case, since the length of PN code per bit is very short compared to the period of the PN code, the performance of the conventional system is not satisfied in view of suppressing the multipath interference. However, the correlation property of the PN codes at the demodulation can be improved by increasing the interval of Integration at the demodulation. This paper proposes a demodulation method to reduce the cross correlation among PN codes. The performance of the proposed demodulation method is investigated through computer simulations. We used multipath Ray lading channel and AWGN channel in the simulation. Our simulation results show the improved performance of $0.25{\sim}0.5dB$ SNR in a given BER compared to the conventional demodulation scheme.