• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.726-733
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• 2010

This paper propose the printed inverted-F antenna using the coupling feed for the mobile phone. The coupling feed can normally leads the additional capacitances in the antenna, so the high inductive reactance of the antenna can be partly compensated. In this paper, it is shown that the bandwidth of the proposed antenna using the coupling feed is improved at $824{\sim}960$ MHz and $1,710{\sim}2,390$ MHz. Then it is compared with the simple direct feed to confirm the improvement of the bandwidth. The proposed antenna covers GSM850/GSM950/DCS/USPCS/WCDMA/Wibro and has the maximum gain of －$4.794{\sim}1.648$ dBi and shows omnidirectional patterns over the operating bands.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.3
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• pp.151-156
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• 2013

Android that was made by Google and Open Handset Alliance is the open source software toolkit for mobile phone. In a few years, Android will be used by millions of Android mobile phones and other mobile devices, and become the main platform for application developers. In this paper, the integrated login application based on Google's Android platform is developed. The main features of the mobile combination login application content based on Android are as follows. First, the application has more convenient login functionality than the functionality of general web browser as the web browser of the mobile-based applications(web browser style applications) as well as security features and faster screen(view) capability by reducing the amount of data transfer. Second, the application is so useful for management of ID and Password, and it can easily manage multiple ID information such as message, mail, profile. The results of performance evaluation of the developed application show the functionality that can login many kinds of portal sites simultaneously as well as the ability that can maintain login continuously. Currently, we are trying to develope a couple of the technologies that can insert multiple accounts into one ID and check all information on one screen.

• Journal of The Korean Association of Information Education
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• v.9 no.3
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• pp.533-548
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• 2005

According to the increasing of the internet infrastructure and growth of contents technology, the users can access an education service at anytime and anywhere. In a field of English education, especially, internet technology has enabled learners to communicate with their teachers and multimedia contents technology has been able to provide learner not only lots of interests, but also good effect on English learning. In this paper, we propose a method diagnosing learner's level by using some question-items, which consist of item's type and item's function. Futhermore, the proposed system can support three devices which are PC, PDA, and Mobile Phone on wired and wireless internet communication environments. Also, the system provides multimedia contents including flash movies, image, and audio contents. We have applied the system into real classroom, and we verified that the question-items that system provides has no problem, and our method could improve each learner skill on English education. Therefore, we expect that learner who uses the proposed system will get level-based English learning service at anytime and anywhere.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2674-2685
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• 1997

In this paper, the design and imprlementation of dual-band power amplifier which is used as a critical part for mobile phone to be simultaneously working at a dual band, 800MHz CDAM and PCS frequency band is described. DC operating point of power FET is limited to Class-B to enable long talk time considering that the tyupical power range of CDMA phones in working is around 10 to Class-B to enable long talk time considering that the typical power range of CDMA phones in working is around 10 to 15dBm, i.e., liner range. The power amplifier which employs two GaAs FETs with good linerity at a low operating point has duplexer cuplexer circuit to separate two frequency bands at input and output stage. Electromagnetic analysis for via holes and coupling between narrow transmission lines is included to design a circuit. Moduld size of 0.96CC($22{\times}14.5{\times}3mm^3$) and maximum module current of 130mA at output power range, 10 to 15dBm are attained. The power amplifer module has achieved ACPR performance with 2 to 3dB marging from IS-95 requirement at output powers, 23.5dBm for PCS and 28dBm for 800MHz CDMA respectively.