• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.1
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• pp.46-54
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• 2000

In this paper, PIFA on PCS handset for SAR reduction is designed. According to the position of PIFA attached on the handset, side mounted PIFA and top mounted PIFA are suggested. Resonance characteristics with variety of design parameters are analyzed. And monopole antenna with $\lambda$/4 length is designed and compared with PIFAs in bandwidth and SAR. At 1.83 GHz center frequency, the bandwidth of side mounted PIFA and monopole antenna are 8.2% and 21.7%, respectively. The 1 g and 10 g peak average SARs of side mounted PIFA are 0.686 and 0.353 respectively, which are about 1/3 of SARs of monopole antenna, 1.759 and 0.978, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.1
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• pp.84-92
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• 2000

A GaAs MESFET MMIC transmitter for 2.4 GHz wireless local loop handset is designed and fabricated. The transmitter consists of a double balanced active mixer and a two stage driver amplifier with voltage negative feedback. In particular, a pair of CS-CG(common source-common gate) structure compensates the reduction in dynamic range caused by unbalanced complementary IF input signals. And to suppress the leakage local power at RF port, the mixer is designed by using phase characteristic between the ports of MESFET. At the bias condition of 2.7 V and 55.2 mA, the fabricated MMIC transmitter with chip dimensions of $0.75\times1.75 mm^2$ obtains a measured conversion gain of 38.6 dB, output $P_{idB}$ of 11.6 dBm, and IMD3 at -5 dBm RF output power of -31.3 dBc. This transmitter is well suited for WLL handset.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.363-367
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• 1999

As the subscription rate to both Internet services and wireless communications services increases rapidly, traffic in the future wireless communications will be dominated by Internet applications. Current research for wireless technology is focused to the multimedia data transmission mainly for the personal computer or notebook whose display which has large display and abundant memory. But in the near future, Internet access request from the handphone or PDA device which is already spreaded in the world will be large. Special handset terminals which has small display monitor, low capacity memory and poor processing power has to be managed differently from torrent wireless communications protocols. So, WAP Forum is organized with wireless handset manufacturers in the world and the standardization process for wireless application is being actively developed. In this paper, basic model and architecture of WAP is introduced and adaptation requirements for change from HTML documents to WML formats are proposed. Also, compression ratio gained in the transform from the existing web documents to WML is shown.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.784-795
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• 2007

In this thesis, the Multi element antenna with wideband and enhanced gain characteristic is proposed to operate at both frequency range from 824 MHz to 896 11Hz for the CDMA and frequency range from 908.5 MHz to 914 MHz for the RFID band. The proposed antenna has tile size of $35{\times}15{\times}5mm^3$ in order to put it in the A model of S company and each element of the proposed antenna is folded to obtain the minimum size. To obtain the antenna with wideband and high gain characteristic, the radiator of the antenna is divided into 4 elements. As a result, bandwidth of the proposed antenna become broader and lower center frequency is appeared due to increased and lengthened current path. Moreover, the enhanced gain characteristic is verified because divided element structure that induct uniform current distribution can get increased antenna efficiency. To attain more uniform current distribution, modified structure of the feeding point that can deliver currents directly is designed. The antenna that alters the feeding structure has higher gain value. Each element is folded to increase the current paths considering the current directions to attain the miniaturization of the antenna. To measure the handset antenna, the handset case must be considered. Even though antenna is designed for predicted characteristic, the resonance frequency is shifted and antenna gain is deteriorated at predicted frequency while antenna is set in the handset case. 1.08 GHz of the resonant frequency is determined after frequency shift from 150 MHz to 200 MHz is confirmed and the maximum gain is measured as 3.1 dBi while antenna is not set in the handset. In case handset case is considered, the experimental results show that the impedance bandwidth for VSWR<2 is from 0.824 GHz to 0.936 GHz(110 MHz). This result appears that the proposed antenna can cover both CDMA and RFID band at once. The measured gain is from -3.4 dBi to -0.5 dBi and it has omni-directional pattern practically.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.903-908
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• 2005

In this paper, in order to consider SAR(Specific Absorption Rate) problem at the beginning stage of a handset development, we investigated the Shh value change by using simulation method according to various EMI(Electromagnetic Interference) paint patterns on front case of a handset and folding angles. First, we made some experiments with EMI paint pattern on front case of a handset, and obtained results showed that different patterns of EMI paint had different SAR values. Among the simulation results on SAR value according to EMI paint patterns, the hairpin pattern showed the best performance, i.e. the decrease efficiency of $8.04\%$ and completely removed pattern showed the decrease efficiency of $5.94\%$. Orignal pattern was set as the reference and the folding angle was $150^{\circ}$. Second, simulation was carried out with changing folding angle from $150^{\circ}$ to $140^{\circ}$ and $160^{\circ}$. Simulation results for the modeled handset showed that SAR value was decreased with increasing the folding angle. When the folding angle was $160^{\circ}$ and with original pattern, we got the SAR value of about 1,61 W/kg. When we applied hairpin pattern with the folding angle of $160^{\circ}$, we got the lowest SAR value of about 1.45 W/kg.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1856-1862
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• 2010

Last rapidly changing mobile handset market in many industries, as well as market conditions affect the prevalence of various content types of consumer spending in general is affecting. Changes in mobile handset market by separating the various consumer-tier analysis, or differentiated in consumers' purchasing behavior are being reflected in the property analysis and overview of customer satisfaction can be assessed by measuring. These mobile devices and the purchase of the devices to investigate the tendency to analyze and weigh the various content industries, you can see how important one can be considered. The development of mobile communication systems and wireless internet and multimedia applications can lead the industry accelerated. In this study, tried to investigate that the mobile communication systems in consideration of the special form of mobile handsets, and customer satisfaction of mobile phone handsets, and the relationship between customer loyalty. Outcome of this study, the mobile properties and the mobile handset brand, price, design and related details to be statistically significant variables were analyzed. In this study, the characteristics of future mobile handset market with a wide range of content-based guidelines for the development of the industry is expected to be able to provide.

• Journal of Digital Convergence
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• v.8 no.1
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• pp.109-120
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• 2010

Mobile phone-related industries have been mainly concentrated on attracting the new customers and increasing the market share such as for the aggressive marketing activities, but it is the time to find an effective strategy to preserve existing customers since the mobile phone market had already reached the saturation. In this study, the properties of mobile phone that influence on the choice of handset and telecom company were analyzed. General properties of respondents were explored and the mobile phone properties were grouped by common factors. And analyzed the effect of factors on customer satisfaction with structural equation model. 10.4% of respondents are used their handset more than two years and 48.7% wanted to purchase other manufacturer's handset if they repurchase mobile phone. These results might come form the fact that the life cycle of mobile phone become shorter by the heating competition in mobile phone market and, to some degree, the influence of smart phone which recently become globally popular. Four factors, 'Hardware Quality', 'Practicality', 'Convergence Functions' and 'Level of Awareness', are induced from the mobile phone properties. In Structural Equation Model analysis, 'Hardware Quality' and 'Practicality' have significant and positive effects on Customer Satisfaction. But, 'Awareness' such as brand and trend appeared quite less influence on the customer satisfaction.

• 한국ITS학회:학술대회논문집
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• 2003.11a
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• pp.192-196
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• 2003

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.253-253
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• 2006

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.504-504
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• 2006