• 한국전자파학회논문지
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• 제17권8호
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• pp.713-718
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• 2006

본 논문에서는 하나의 단말기로 다수의 서비스를 제공할 수 있는 5밴드 폴디드 모노폴 안테나를 설계 제작하였다. 폴디드 모노폴 안테나의 접힌 구조를 통한 직렬 커패시턴스 보상과 물리적인 길이를 조절하여 이득을 높일 수 있는 특성을 이용하였다. 이 안테나는 CDMA/GSM/DCS/USPCS/WCDMA 5밴드 대역 특성을 만족하고 있으며, 제작에 있어서도 기존의 프레스 제작 형태가 아닌 유연성 기판(flexible PCB) 기술을 이용함으로써 낮은 생산 가격을 실현하였다 정합단을 적용한 안테나는 5밴드 대역에서 최대 이득 $-2.51{\sim}+1.82 dBi$ 결과가 나왔고, 방사 패턴 또한 전방향성 특성을 얻었다.

• 한국전자파학회논문지
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• 제17권9호
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• pp.821-828
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• 2006

본 논문에서는 시험용 휴대폰의 내부에 위치한 루프 형태 접지판의 위치와 크기 변화에 따른 SAR(Specific Absorption Rate) 값의 변화를 검토하였다. 휴대폰의 rear case 안에 있는 루프 형태 접지판에 따른 SAR 값에 대한 전산 모의 실험을 수행하였으며 그 결과 루프 형태 접지판의 위치와 크기에 따라 SAR 값이 달라짐을 보였다. 검토된 루프 형태 접지판의 위치와 크기들 중 small size case-C의 경우가 8.70 %의 감소 효율을 보여 가장 좋은 성능을 보였다. 그리고 이 경우에 루프 형태 접지판에 가장 높은 유도 전계 분포를 보였다. 전산 모의 실험시 폴딩 각도는 $160^{\circ}$로 하였다.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2006년도 하계종합학술발표회 논문 초록집
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• pp.504-504
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• 2006

• JSTS:Journal of Semiconductor Technology and Science
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• 제9권4호
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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.

• ETRI Journal
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• 제33권1호
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• pp.121-124
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• 2011

Digital harmonics, which may reduce the radio frequency sensitivity of a system, can be coupled with an antenna in a mobile handset. This letter presents a decoupling method for increasing the isolation between digital harmonics on a flexible printed circuit board (FPCB) and an antenna in terms of the ground mode current and the concept of reaction. We model the signal and ground lines in an FPCB as a loop circuit exciting a ground mode current and demonstrate a simple but efficient decoupling method for reducing the excited ground mode current.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 추계종합학술대회 B
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• pp.636-639
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• 2008

본 논문에서는 VHF대의 휴대무선 단말기에 사용되는 안테나의 특성개선을 다루고 있다. 일반적으로 VHF대 휴대단말기에 사용되는 안테나는 대부분 1/4파장 모노폴 안테나 또는 헤리컬 안테나이다. 그러나 이와 같은 안테나의 특성은 단말기의 본체를 손으로 잡을 경우 크게 변화되고, 방사효율이수 dB이상 저하되어 안정된 통신이 어렵게 된다. 본 논문에서는 VHF대의 휴대무선 단말기에 있어 사용되는 대표적인 안테나특성을 평가하고, 손으로 잡는 경우를 포함하여 안테나의 방사효율 특성을 개선하는 방법을 제안하고 있다.

• ETRI Journal
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• 제35권2호
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• pp.321-331
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• 2013

High-tech markets are unpredictable owing to rapid technology innovation, diverse customer needs, high competition, and other elements. Many scholars have attempted to explain the uncertainty in high-tech markets using their own various approaches. However, sufficiently clear ways to predict diverse changes and trends in high-tech markets have yet to be presented. Thus, this paper proposes a new approach model, that is, systematic market segmentation, to give more accurate information. Using an empirical dataset from the mobile handset market in the Republic of Korea, we conduct our research model consisting of three steps. First, we categorize nine basic segments. Second, we test the stability of these segments. Finally, we profile the characteristics of the customers and products. We conclude that the approach is able to offer more diagnostic information to both practitioners and scholars. It is expected to provide rich information for an appropriate marketing mix in practice.

• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.151-155
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• 2010

Reconfigurable radio technology is needed to reconstruct frequency and modem functionality, which can be different in various regions. In addition, it makes a single mobile handset capable of supporting various standards of wireless communication and thus plays a key role in mobile convergence. An MMIC VCO (voltage controlled oscillator) has been developed for high power and wide bandwidth where Clapp-Gouriet type oscillators are adapted for series feedback, and was fabricated based on 0.15um pHEMT of TRW. The MMIC VCO was connected to an aluminar substrate on the carrier for testing. This MMIC VCO module showed good performance in comparison to existing works. Furthermore, it can be potentially extended to reconfigure an MMIC VCO for wireless systems such as military applications and satellite communications.

• 유통과학연구
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• 제15권12호
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• pp.53-60
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• 2017

Purpose - This paper analyzes the effect of the handset subsidy and the Mobile Number Portability subscriber subsidy regulation, which are the main regulation adopted in "Law on the Improvement of the Mobile Terminal Distribution System" (Mobile Terminal Distribution Act), on the social surplus, the consumer surplus and profits of telecommunications carriers. We focus our analysis on whether the service charge competition is stimulated enough so that it can compensate for the loss of subsidies. Research design, data, and methodology - We use simple economic model to assess the impact of the handset subsidy and the Mobile Number Portability subscriber subsidy regulation. Unlike the former researches on this topic, we depart from using Hotelling model, and instead use the switching cost model, which uses switching cost as a parameter of market powers of telecommunications carriers. We also study the effect of the two different regulations when they are adopted both independently and concurrently. Results - If the market powers of telecommunications carriers are over certain threshold, contrary to the regulatory agency's assertion, the service charge competition would not be stimulated enough to compensate for the deduction in the subsidies, and thus the consumer surplus is compromised. Number Portability subsidy, especially, undermines the rival's market power and thus reduces the service charge. On the other hand, the regulations will also increase the profits of telecommunications carriers. However, social surplus is maximized when both of the regulations are present because the regulations reduces the frequency of switching handsets inefficiently. Conclusions - In enacting the Mobile Terminal Distribution Act, the telecommunications regulatory agency asserted that the regulation on subsidies will stimulate service charge competition, and in the long run, enhance the consumer surplus. However, contrary to the regulatory agency's assertion, subsidy regulation, especially the regulation on Number Portability subsidy, reduces consumer surplus. On the other hand, the Mobile Terminal Distribution Act can also increase the profits of telecommunications carriers because it decreases competition among the telecommunications carriers. However, the Mobile Terminal Distribution Act can increase the social surplus because it reduces inefficient switching of handsets.

• 한국통신학회논문지
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• 제25권4B호
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• pp.624-628
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• 2000

본 논문에서는 CDMA 단말기의 전기적 성능에 관한 최소의 요구 사항을 명기한 IS-98B의 항목에서 CDMA 파형의 질(Waveform Quality)을 규정하는 항목인 트래픽로(Traffic Rho)가 최소 성능에 만족하지 않을 경우 CDMA 단말기에 나타나는 현상을 분석하고, CDMA단말기 디자인시 단말기 송신부의 IF(Intermediate Frequency)단에서 TX IF SAW FILTER의 매칭회로를 개선하고 송신단 전원인 3.0V -TX를 발생시키는 LDO(Low Dropout Regulator)의 노이즈 발생을 차단하여 트래픽로 문제 해결방법을 제안한다. 제안 방법을 적용한 후의 파형과 적용전의 파형을 HP8924C 와 HP8595E을 이용하여 비교하여 성능을 개선됨을 보였다.