• 한국전자파학회논문지
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• 제20권1호
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• pp.1-11
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• 2009

본 논문에서는 플라즈마 응용을 위 한 고효율 및 고안정성을 가지는 RF 발생기용 1 kW급 전력증폭기를 설계 및 제작하였다. 전력증폭기는 푸쉬풀 MOSFET 1개와 고전류 구동 IC로 구성하였으며, E급 증폭기의 구조를 사용함으로써 효율을 개선하였다. 플라즈마 응용에 적합하도록 전력증폭기에 선택적 감쇠기를 사용하여 3가지 모드로 동작하게 함으로써 효율과 안정성을 선택적으로 고려할 수 있도록 하였다. 초기 방전 구간의 불안정성을 개선하기 위하여 RF 발생기의 출력 안정영역을 선택적 감쇠기를 사용하여 전압정재파비(VSWR)를 3.8:1 미만보다 개선된 4.5:1 미만으로 확장하였다. 또한 기존에 적용되는 증폭기에 비하여 크기를 30 % 줄였으며, 주파수 13.56 MHz, 출력 1 kW에서 효율 80 %를 얻으므로 기존에 비하여 효율을 약 13 % 개선하였다.

• Journal of Communications and Networks
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• 제11권2호
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• pp.196-206
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• 2009

Over the last five years, relaying or multihop techniques have been intensively researched as means for potentially improving link performance of wireless networks. However, the data rates of relays are often limited because they cannot transmit and receive on the same frequency simultaneously. This limitation has come to the attention of researchers, and recently a number of relay techniques have been proposed specifically to improve the data efficiency of relaying protocols. This paper surveys transmission protocols that employ first single relays, then multiple relays and finally multiple antenna relays. A common feature of these techniques is that novel signal processing techniques are required in the relay network to support increased data rates. This paper presents results and discussion that highlight the advantages of these approaches.

• ETRI Journal
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• 제37권4호
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• pp.657-666
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• 2015

We propose a two-stage resource allocation algorithm for the high link utilization of an orthogonal frequency-division multiplexing passive optical network (OFDM-PON). An OFDM-PON is assumed to use a synchronous frame structure in supporting service differentiation. In distributing resources, the proposed algorithm first allocates a time window for each optical network unit (ONU), and then it arranges a subchannel, which is a group of subcarriers. This algorithm needs to satisfy two constraints. First, computations for the resource allocation should be done using a frame unit. Second, an ONU has to use a single subchannel to send upstream data for multiple services within a frame duration. We show through a computer simulation that the proposed algorithm improves the link utilization.

• ETRI Journal
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• 제35권2호
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• pp.177-187
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• 2013

In this paper, we propose a dual-band multiple-input multiple-output (MIMO) antenna with high isolation for WLAN applications (2.45 GHz and 5.2 GHz). The proposed antenna is composed of a mobile communication terminal board, eight radiators, a coaxial feed line, and slots for isolation. The measured -10 dB impedance bandwidths are 10.1% (2.35 GHz to 2.6 GHz) and 3.85% (5.1 GHz to 5.3 GHz) at each frequency band. The proposed four-element MIMO antenna has an isolation of better than 35 dB at 2.45 GHz and 45 dB at 5.2 GHz between each element. The antenna gain is 3.2 dBi at 2.45 GHz and 4.2 dBi at 5.2 GHz.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2003년도 가을 학술발표논문집 Vol.30 No.2 (2)
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• pp.661-663
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• 2003

In this paper, we present new methods for rapid high-resolution range sensing using green-blue stripe pattern. We use green and blue for designing high-frequency stripe projection pattern. For accurate and reliable range recovery, we identify the stripe patterns by our color-stripe segmentation and unwrapping method. The experimental result for a naked human face shows the effectiveness of our method.

• 한국통신학회논문지
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• 제18권5호
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• pp.739-745
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• 1993

이동통신 기기에서 온도에 대해서 고안정의 주파수 합성기를 구현함은 중요하다. 그런데, 고안정의 주파수 합성기를 구현하기 위해서는 기준 주파수를 제공하는 발진기가 온도에 대해서 안정해야만 한다. 본 논문에서는 이러한 필요성에 따라서 디지털 방식을 이용한 TCXO가 구현된다. DTCXO는 온도 감지부, 제어부, VCXO로 나뉜다. 구현된 DTCXO의 주파수 안정도는 평균 0.94ppm이다. 이는 아나로그 방식을 이용한 TCXO의 안정도인 2.5ppm과 비교해볼 때, 향상된 결과이다.

• 전자공학회논문지A
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• 제33A권3호
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• pp.38-46
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• 1996

The purpose of this study is to develop the miniaturized duplexer filter for mobile communications using high dielectric constant (${\varepsilon}$r > 100, 180) ceramic resonators. Duplexer filter was ocmposed of ceramic resonators which has been developed using BNT system and SCT system, respectively. Developed duplexer filter was formed to have Tx frequency band at 836.5 (($\pm$12.5)MHz and Rx frequency band at 881.5 ($\pm$12.5)MHz. Insertion loss at Tx frequency band was 1.41dB and 1.46dB, insertion loss at Rx frequency band was 3.49dB and 3.65dB, respectively. Especially, duplexer filters using dielectric cermaics with ${\varepsilon}$r = 180 were 8% smaller than commercially manufactured duplexer filters using dielectric ceramics with ${\varepsilon}$r = 90 by murata.

• 전기전자학회논문지
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• 제3권1호
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• pp.39-49
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• 1999

This paper describes a 1 GHz, low-phase-noise CMOS fractional-N frequency synthesizer with an integrated LC VCO. The proposed frequency synthesizer, which uses a high-order delta-sigma modulator to suppress the fractional spurious tones at all multiples of the fractional frequency resolution offset, has 64 programmable frequency channels with frequency resolution of $f_ref/64$. The measured phase noise is as low as -110 dBc/Hz at a 200 KHz offset frequency from a carrier frequency of 980 MHz. The reference sideband spurs are -73.5 dBc. The prototype is implemented in a $0.5{\mu}m$ CMOS process with triple metal layers. The active chip area is about $4mm^2$ and the prototype consumes 43 mW, including the VCO buffer power consumption, from a 3.3 V supply voltage.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.345-348
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• 2002

A complementary VHF CMOS active inductor is described. The proposed circuit employs 'p-type' and 'n-type' active inductor to obtain enlarged signal handling ability. Under the same inductance, Q value, and power consumption, the proposed circuit shows more than 12-㏈ improvement in dynamic range while maintaining high-frequency operation. Further enhancement is obtained by using a fully differential floating inductor structure. A 1-㎓ 4$\^$th/-order coupled-resonator filter is designed to demonstrate the potential of the proposed active inductor.

• Journal of Communications and Networks
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• 제15권5호
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• pp.457-463
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• 2013

In recent days, cooperative diversity and communication security become important research issues for wireless communications. In this paper, to achieve low probability of interception (LPI) and high throughput in the cooperative single-carrier frequency division multiple access (SC-FDMA) system, a new physical layer transmission scheme is proposed, where a new encryption algorithm is applied and adaptive modulation is further considered based on channel state information (CSI). By doing so, neither relay node nor eavesdropper can intercept the information signals transmitted from user terminal (UT). Simulation results show above new physical layer transmission scheme brings in high transmission safety and secrecy rate. Furthermore, by applying adaptive modulation and coding (AMC) technique according to CSI, transmission throughput can be increased significantly. Additionally, low peak-to-average power ratio (PAPR) characteristic can still be remained due to the uniform distribution of random coefficients used for encryption algorithm.