• JSTS:Journal of Semiconductor Technology and Science
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• 제11권4호
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• pp.247-255
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• 2011

This paper describes a CMOS outphasing transmitter using two wideband phase modulators. The proposed architecture can simplify the overall outphasing transmitter architecture using two-point phase modulation in phase-locked loop, which eliminates the necessity digital-to-analog converters, filters, and mixers. This architecture is verified with a WCDMA signal at 1.65 GHz. The prototype is fabricated in standard 130 nm CMOS technology. The measurement results satisfied the spectrum mask and 4.9% EVM performance.

• Journal of electromagnetic engineering and science
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• 제11권2호
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• pp.128-132
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• 2011

In interference tolerance based spectrum sharing systems, primary receivers (PRs) are protected by a predefined peak or average interference power constraint. To implement such systems, cognitive radio (CR) transmitters are required to adjust their transmit power so that the interference power received at the PR receivers is kept below the threshold value. Hence, a CR-transmitter requires knowledge of its channel and the primary receiver in order to allocate the transmit power. In practice, it is impossible or very difficult for a CR transmitter to have perfect knowledge of this channel state information (CSI). In this paper, we investigate the impact of imperfect knowledge of this CSI on the performances of both a primary and cognitive radio network. For fixed transmit power, average interference power (AIP) constraint can be maintained through knowledge of the channel distribution information. To maintain the peak interference power (PIP) constraint, on the other hand, the CR-transmitter requires the instantaneous CSI of its channel with the primary receiver. First, we show that, compared to the PIP constraint with perfect CSI, the AIP constraint is advantageous for primary users but not for CR users. Then, we consider a PIP constraint with imperfect CSI at the CR-transmitter. We show that inaccuracy in CSI reduces the interference at the PR-receivers that is caused by the CR-transmitter. Consequently the proposed schemes improve the capacity of the primary links. Contrarily, the capacities of the CR links significantly degrade due to the inaccuracy in CSI.

• 한국인터넷방송통신학회논문지
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• 제14권3호
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• pp.43-49
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• 2014

마크-젠더 변조기와 저역 통과 필터를 사용하여 광 듀오바이너리 신호를 생성하는 광 듀오바이너리 송신기의 전송 특성을 40Gbps에서 이론적으로 분석하였다. 광 듀오바이너리 시스템의 전송 성능은 송신기를 구성하는 저역 통과 필터와 광 필터 그리고 수신기내 필터의 대역폭에 따라 차이를 보였으며 각 필터들은 광 파워 스펙트럼에 각기 다른 영향을 주었다. 필터들의 최적화된 대역폭을 선택함으로써 광 듀오바이너리 신호 전송 시 부엽 발생과 리플을 억제시키고 분산 내성을 개선 할 수 있었다.

• 한국인터넷방송통신학회논문지
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• 제17권2호
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• pp.89-94
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• 2017

본 논문은 마크-젠더 변조기를 사용하여 광 신호를 생성하는 광 듀오바이너리 송신기들의 전송 특성을 이론적으로 분석하였다. 특히 단일 모드 광섬유를 통하여 분산 보상 방법에 대한 고려 없이 1550nm 파장에서 25Gbps 광 듀오바이너리 신호를 전송하는 여러 가지 형태의 송신기들에 대한 성능을 평가하였다. 각 송신기의 특성에 따라 광 듀오바이너리 신호 생성 방법이 다르기 때문에 광 파워 스펙트럼과 광 신호의 눈 열림에 특징이 있었으며 이로 인하여 전송 거리에 따른 분산 내성도 차이를 보였다. 모의실험 결과와 송신기 구조의 복잡성 및 제한 조건을 고려하여 25Gbps 전송에 적합한 송신기를 확인 할 수 있었다.

• 한국통신학회논문지
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• 제19권4호
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• pp.729-739
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• 1994

중앙집중 대역확산 패킷라디오 네트워크를 위한 다원접속 방식으로 임의할당-송신기 프로토콜을 새로이 제안한다. 제안하는 임의할당-송신기 프로토콜은 프리엠블 전송시만 경쟁모드로 동작하고, 데이터부분은 의사 직교특성을 갖는 송신기별 확산코드를 사용한다. 종래의 송신기별 프로토콜과 비교할때, 임의 할당-송신기 프로토콜은 프리엠블 전송을 위해 적은 수의 확산코드를 사용하는 경우 중앙수신기의 복잡도를 크게 줄일 수 있다. 이론적인 처리율 분석과 시뮬레이션 결과를 통해 단지 2~3개의 확산코드를 사용하여 프리엠블을 전송하는 경우에 성능이득의 대부분을 얻을 수 있었다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권4호
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• pp.238-246
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• 2011

A 3-5 GHz UWB radar chip in 0.13 ${\mu}m$ CMOS process is presented in this paper. The UWB radar transceiver for surveillance and biometric applications adopts the equivalent time sampling architecture and 4-channel time interleaved samplers to relax the impractical sampling frequency and enhance the overall scanning time. The RF front end (RFFE) includes the wideband LNA and 4-way RF power splitter, and the analog signal processing part consists of the high speed track & hold (T&H) / sample & hold (S&H) and integrator. The interleaved timing clocks are generated using a delay locked loop. The UWB transmitter employs the digitally synthesized topology. The measured NF of RFFE is 9.5 dB in 3-5 GHz. And DLL timing resolution is 50 ps. The measured spectrum of UWB transmitter shows the center frequency within 3-5 GHz satisfying the FCC spectrum mask. The power consumption of receiver and transmitter are 106.5 mW and 57 mW at 1.5 V supply, respectively.

• Journal of Communications and Networks
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• 제8권2호
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• pp.144-150
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• 2006

A serious problem with traditional 'command & control' spectrum management techniques is that they do not easily accommodate new technologies and new services. This paper describes the necessary principles of flexible-use spectrum rights which may allow a wide variety of spectrum uses in a single general-purpose band. Based on the electrospace description of the radio spectrum, these principles allow general aggregation or division of licensed electrospace regions via secondary markets, providing rules for how regulatory limits change under aggregation or division. These flexible-use principles limit transmitter behaviors that tend to create a more difficult operating environment for receivers, while making receivers responsible for handling any remaining interference. The author shows how flexible-use principles could provide a basis for real-world flexible-use frequency bands.

• Journal of Communications and Networks
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• 제16권2호
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• pp.110-120
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• 2014

This article proposes a spectrum sharing method which can avoid the mutual interference in both primary and secondary systems. The two systems make them a priority to use two single-dimension orthogonal signals, the real and imaginary pulse amplitude modulation signals, if the primary system is not in outage with this use. A secondary transmitter is selected to be the primary relay and the active secondary source to perform this. This allows a simultaneous spectrum access without any mutual interference. Otherwise, the primary system attempts to use a full two-dimensional signal, the quadrature amplitude modulation signal. If there is no outage with respect to this use, the secondary spectrum access is not allowed. When both of the previous attempts fail, the secondary system is allowed to freely use the spectrum two whole time slots. The analysis and simulation are provided to analyze the outage performance and they validate the considerable improvement of the proposed method as compared to the conventional one.

• 한국통신학회논문지
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• 제28권6A호
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• pp.425-432
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• 2003

본 논문에서는 직접변환방식을 이용한 CDMA 기지국용 멀티캐리어 디지털 송신기를 설계하고 시뮬레이션을 통해 그 성능을 검증해 보았다. 먼저, 멀티캐리어 송신기를 설계하기 위해 필요한 새로운 기술들을 검토해보고, 이 새로운 기술을 적용하여 멀티캐리어 송신기를 설계하고 시뮬레이션 하였다. 설계와 시뮬레이션은 Agilent Technologies사의 RF 시뮬레이션 S/W인 ADS (Advanced Design System)을 사용하였으며, 디지털 블록과 아날로그 블록으로 나누어 설계한 후 두 블록을 co-simulation하여 결과를 분석하였다. 결과에 의하면, 직접변환방식을 이용하여 멀티캐리어 디지털 송신기를 구현한 경우 최종 아날로그출력이 시스템의 요구조건 (IS-97 & 3G TS 25.104) 인 스펙트럼 마스크 특성을 만족하였다. 이것은 제안한 멀티캐리어 디지털 송신기의 성능이 CDMA 기지국에 적용될 수 있다는 것을 의미한다. 따라서, 본 논문에서 제안한 직접변환방식을 이용한 멀티캐리어 디지털 송신기는 향후 CDMA 기지국에 적용되어 구현될 때, 가격적으로나 기술적으로 한 단계 발전된 시스템을 구현할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권12호
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• pp.4946-4960
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• 2020

In a device-to-device (D2D) underlaid cellular network, there exist two types of co-channel interference. One type is inter-layer interference caused by spectrum reuse between D2D transmitters and cellular users (CUEs). Another type is intra-layer interference caused by spectrum sharing among D2D pairs. To mitigate the inter-layer interference, we first derive the interference limited area (ILA) to protect the coverage probability of cellular users by modeling D2D users' location as a Poisson point process, where a D2D transmitter is allowed to reuse the spectrum of the CUE only if the D2D transmitter is outside the ILA of the CUE. To coordinate the intra-layer interference, the spectrum sharing criterion of D2D pairs is derived based on the (signal-to-interference ratio) SIR requirement of D2D communication. Based on this criterion, D2D pairs are allowed to share the spectrum when one D2D pair is far from another sufficiently. Furthermore, to maximize the energy efficiency of the system, a resource allocation scheme is proposed according to weighted graph coloring theory and the proposed ILA restriction. Simulation results show that our proposed scheme provides significant performance gains over the conventional scheme and the random allocation scheme.