• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.634-641
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• 2000

A switchable VCO for DECT handset is designed and fabricated. In dual mode radios, a single VCO is desired to operate at two different frequencies to meet the requirement of two mode(Tx, Rx). The three design types of switchable VCO are switched resonator VCO, switched mode VCO and dual band VCO. In this paper, we use the switched resonator VCO type using pin diode switch to change the total amount of capacitance in the tank circuit. At the bias condition of 3 V and 13mA, the output power and phase noise are better than6.5dBm and -104dBc/Hz at 25khz offset from the carrier, respectively , across the operating frequency range. From these results, the fabricated switched VCO is applicable to the DECT handset.

• Journal of IKEEE
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• v.19 no.2
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• pp.124-132
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• 2015

In this paper, we proposed a multiband internal antenna for LTE mobile handset that could be used for mobile devices. The proposed antenna has a volume of $50mm(W){\times}21mm(L){\times}5mm(H)$, ground plane size is $60mm(W){\times}100mm(L)$, and covers 9 service frequency bands including LTE(Long Term Evolution) band with VSWR(Vlotage Standing Wave Ratio) less than 3. With rapid change of technologies, people wants to include more function into one device. In addition, each country uses different frequency band for traffic service, it is necessary to design multiband antenna for mobile phone since traveling foreign country needs roaming. And if we can cover several services with one antenna, cost and volume needed for antennas are minimized. A HFSS (High Frequency Structure Simulator) of the Ansoft Corporation based on a finite element method is employed to analyze the proposed antenna in the design process and to compare the simulation and experimental results.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.515-517
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• 2003

In this paper we examine the effects of the required portions of guard timing spaces in a MAC frame of ETSI BRAN HIPERLAN/2 system such as inter-mobile guard timing space in UL(Up Link) duration, inter-RCH(Random CHannel) guard timing space, sector switch guard timing space. In particular, we calculate the number of OFDM(Orthogonal Frequency Division Multiplexing) symbols required for these guard timing spaces in a MAC frame. We them evaluate the throughput of HIPERLAN/2 system as we vary parameter such as the guard time values defined in [2], the number of DLCCs(Data Link Control Connections), and the number of RCHs. Finally we show by numerical results that the portions for the 새심 summation of required guard timing spaces in a MAC frame are not negligible, and that they should be properly considered when trying to evaluate the performance of MAC protocol of HIPERLAN/2 system and also when determining the number of RCHs as well as the number of DLCCs in UL PDU trains at an AP/CC(Access Point/Central Controller).

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.6
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• pp.41-56
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• 2007

In this paper, we propose a specification-based intrusion detection system for WIPI(Wireless Internet Platform for Interoperability). In proposing the system, we focused on providing lightweight code, supporting multiple languages and hardware independence. The proposed system is based on an algorithm which detects an intrusion to main API of WIPI-HAL(Handset Adaptation Layer) and defines the prototype of mIDS(mobile IDS) API group that it can be added on the HAL. Moreover, we prove apply possibility through a WIPI emulator using java library.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.11
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• pp.8-16
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• 2000

In this paper, on calculating SARs on human head using computer simulation, SARs caused by PCS handsets are calculated and compared, and the design parameters that affect SAR values are analyzed. Is and 10 g peak averaged SARs are calculated as the type of antenna, the location of antenna, and the type of handset are changed and SAR distributions as depth of human head are shown. Among the antennas on flip type handsets, side mounted PIFA has the lowest SARs 1g and 10g peak averaged SARs are 0.686W/kg and 0.353W/kg. The SARs caused by monopole antenna on folder type handset are 1.133W/kg and 0.709W/kg. and are about 30% lower than monopole 1.759W/kg and 0.978W/kg, respectively. SAR distributions as depth of human head of side mounted PIFA and monopole antenna on folder-type handset are more slowly changed than those of top mounted PIFA and monopole antenna on flip-type handset.

• Communications of the Korean Institute of Information Scientists and Engineers
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• v.28 no.11
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• pp.9-22
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• 2010

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.947-951
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• 2008

Subsidiary business between mobile carriers and handset manufacturers has been banned by Korean regulator due to the concern that it may cause the unfair competition in the market. But the opinion that the current regulation has to be consolidated is increasing to follow recent market trends, ensuer the fair competition and increase the users' benefit. In this paper, I analysed trends of the mobile telecommunication market and proposed desirable direction of regulatory improvement.

• ETRI Journal
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• v.31 no.5
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• pp.598-600
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• 2009

A highly efficient and compactly integrated balanced power amplifier (PA) for W-CDMA handset applications is presented. To overcome the size limit of a typical balanced PA, a bulky input divider is integrated into a PA MMIC, and a complex output network is replaced with simple lumped-element networks. For efficiency improvement at the low output power level, one of the two amplifiers in parallel is deactivated and the other is partially operated with corresponding load impedance optimization. The implemented PA shows excellent average current consumption of 34.5 mA in urban and 56.3 mA in suburban environments, while exhibiting very good load-insensitivity under condition of VSWR=4:1.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.249-256
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• 2009

As a wireless handset deals with multiple application standards concurrently, RF transmitters and power amplifiers are required to be more power efficient and reconfigurable. In this paper, we review the recent advances in the design of the power amplifiers and transmitters. Then, the systematic design approaches to improve the performance with the digital baseband signal processing are introduced for the next generation mobile handset.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.443-447
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• 2005

The SAR measurement system with stationary probes, presented in this paper, can calculate area SAR value based ell the measured 9 electric field data. By converting obtained area SAR to the volume SAR, the results can be acquired in a few seconds. The system can be very useful tool in the stages of handset development for mobile communication as well as in the handset production line because of its rapid SAR measurement. The system showed good linearity characteristics at 835 MHz of 10 $\sim$ 27 dBm input power range.