• Journal of Navigation and Port Research
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• v.34 no.3
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• pp.167-173
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• 2010

In order to design small printed antenna restricted within narrow area of $30mm{\times}8mm$ for the Zigbee module and improve its return loss, meander slot antenna with a floating conductor as the parastic element has been proposed. The resonant frequency and bandwidth(VSWR${\leq}$2) of the antenna designed and fabricated in the present study is about 2.44GHz and 113MHz respectively. The radiation pattern is almost similar to that of dipole antenna within the operation frequency range. Also the radiation efficiency and gain of the proposed antenna is more than 60% and 2.7dBi respectively. It has been observed that the characteristics the proposed antenna mentioned above satisfy the specification required of the Zigbee application. In order to validate the proposed antenna, some simulated and measured results are presented and compared.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1919-1926
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• 2016

Because of the enormous processing ability, General-Purpose Graphics Processing Unit(GPGPU) has been applied to many fields including electronics design automation. The SAT algorithm is one of the core algorithm in many electronics design automation tools. There has been some efforts to apply GPGPU to the SAT algorithm, but it is difficult to parallelize the SAT algorithm because of its characteristics. In this paper, I applied GPGPU to the SAT algorithm by parallelizing the propagation routine that is relatively suitable to parallel processing. On the basis of the similarity of the propagation routine to the sparse matrix multiplication, the data structure for the SAT problem is constituted, and the parallel propagation routine is described. To prevent data loss between paralllel threads, atomic operations are exploited. The experimental results for some benchmark SAT problems show that the proposed algorithm is superior to the previous GPGPU-based SAT solver.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.5 no.4
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• pp.198-205
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• 2012

This study deals with development of an evaluating tool for flow experience and presence to evaluate interactive digital contents. The tool is able to measure the grade of flow and presence by surveying with their factors which are known to affect flow experience and presence. One of reasons for reducing flow experience and presence in 3D digital contents is that the experience in the virtual world is different from user's prerequisite learning in the real life. The recent interactive contents using physical movement of users as an input is possible to provide unsafe situation to users due to the different experience. The suggested flow measurement tool is able to evaluate presence and flow experience of an interactive 3D contents as well as flow and presence factors are possible to use as a general guideline for all stages of producing interactive 3D digital contents.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.211-220
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• 2018

The standard data link layer encryption provided by CCSDS has a structure that encodes HDLC frame into it using an AES algorithm. However, CCSDS is standard method has a structure in which the receiving side cannot request a re-activation when noise interference occurs over an unstable channel. SES Alarmed has a structure that enables the receiving side to additionally detect errors and perform re-activation requests in an operational structure similar to that of link encryption in CCSDS. The SES Alarmed related paper was intended to identify the optimum range of thresholds and identify data corruption due to channel noise. In this paper, the focus was on reducing the re-activation process if the HDLC frame, excluding the password Sync code, consistently exceeds any threshold levels. The HDLC frame order was changed and the results of using SES Alarmed were proposed and compared.

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.74-81
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• 2010

A modeling methodology for the analysis of injection-locked Fabry-Perot laser diodes (FP-LDs), promising for cost-effective WDM-PON sources, is proposed. The time-domain large-signal model that is used is found to provide quite similar results to some experimental ones. With our methodology, we model characteristics of FP-LDs, such as influence of reflectivity at a facet and detuning on injection-locking. The eye diagram characteristics are also investigated. It is observed that the facet reflectivity at the injection side should be lower than 1% to provide stable operation in terms of good side-mode suppression ratio and independence from detuning between narrow-band injection noise and LD modes. It is also observed that good eye opening can be obtained for 155 Mbps modulation while the parameters such as the active region thickness should be properly optimized to obtain reasonable eye opening at 1.25 Gbps.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.37-44
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• 2005

This paper proposes a hybrid scheme for dynamic bandwidth allocation(DBA) in Ethernet passive optical network(EPON), which combines advantages of adaptive cycle and constant cycle-based schemes. The proposed scheme is based on IPACT scheme, but it operates as adaptive cycle or constant cycle mode according to the queue status of optical line terminal(OLT) for downstream transmission. Simulation results showed that the proposed scheme could achieve a similar throughput in downstream transmission to a constant cycle-based DBA scheme, while producing a similar delay performance to the IPACT scheme in upstream transmission.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.2
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• pp.35-43
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• 2011

In this paper, an analysis on I/Q mismatch characteristics of a quadrature LC VCO(Voltage controlled oscillator) is presented. Based on this analysis, a new I/Q mismatch compensator is proposed. The proposed I/Q mismatch compensator utilizes an amplitude mismatch detector rather than the conventional phase mismatch detector requiring much more wide frequency bandwidth. To verify the proposed circuit, a 2.5GHz quadrature LC VCO was designed in a $0.18{\mu}m$ CMOS process and tested. Test results show that an amplitude mismatch detector achieves similar I/Q mismatch compensation performance as that of the conventional phase mismatch detector. The I/Q mismatch compensator consumes 0.4mA from 1.8V supply voltage and occupies $0.04mm^2$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.54-61
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• 2007

A variable gain low noise amplifier (VG-LNA) implemented in TSMC 0.18 um process is presented. This VG-LNA is designed of two stage amplifier, and its gain is controlled by the shunt feedback loop composed of a gain control transistor (GCT) and a coupling capacitor in second stage. The channel resistance of GCT in the shunt feedback loop influences the input and output stages of a second stage by the Miller effect. Total gain of the proposed VG-LNA is changed by two factors, the load impedance reduction and the interstage mismatch by controlling the channel resistance of the GCT. Consequently, by adding a shunt feedback with a gain control transistor, this proposed VG-LNA achieves both wide gain tuning range of 37 dB and continuous gain control simultaneously.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.193-197
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• 2015

Recently, the new issues for the safety and the information delivery system in the ship are raised. The deployment and the efficient algorithms of deploying the wireless sensor networks instead of using the built-in wired networks or the setup of the new wired networks is more desirable than the deployment of the wired networks in a ship after its final production since it can reduce the cost and the time of the brand new wired networks by reshaping some of the internal structure of the ship. In this paper, the shipboard signal propagation measurement system based on the signature sequence-three way slave mode are designed and its measureed data are analysed after measuring the signal propagation characteristics. Consequently, it is expected that the reliable and cost-effective signal measurement system with the three way algorithm for the deployment of the shipboard wireless networks can be achieved.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.10
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• pp.1427-1434
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• 2013

In this paper, triple band mobile chip antenna for DCS(1.71~1.88GHz) / PCS(1.75~1.87GHz) / UPCS(1.85~1.99GHz) on PCB Layout is designed. To analyze the characteristics of the designed antenna, we designed and measured Single, Dual, Triple Band antenna. The designed antenna was fabricated and measured using vector network analyzer in LTK(Laird Technologies Korea). Triple and wide band characteristic could be realized the measured bandwidth(V.S.W.R<2.0) of designed antenna operated in the band of 1.71GHz~1.99GHz. This antenna has a small size of about $19mm{\times}4mm{\times}1.6mm$, narrow bandwidth which is a defect of chip antenna is improved. And its experimental results were a good agreement with simulation performance.