• Title, Summary, Keyword: 피드포워드방식

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A Technique Combining the Nonlinear Compensation and the Path Calibration by Using the Feedforward Scheme in Transmitting Array Antenna Systems (피드포워드 방식을 이용한 송신 배열 안테나의 비선형 보상과 경로 보정의 결합 기술)

  • Kim, Min;Eun, Chang-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.4A
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    • pp.197-204
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    • 2012
  • We propose a new scheme combining the compensation of HPA nonlinearity and the calibration of the path imperfections in the downlink OFDM smart antenna systems. We use a two term third-order polynomial (without second-order term) and the feedforward method for compensation and calibration to make each path of the antenna array have equal characteristics. Since the proposed scheme does not alter the base-band signal, it can be applied to the smart antenna system independently of the base-band signal processing section. The result of computer simulations shows that, with the addition of only one third-order term, the adverse nonlinear effects can be effectively compensated, and the those of linear imperfections can be calibrated as well.

Circuit Parameter Optimization and Significantly Enhanced ACPR of W-CDMA Signals of Feedforward Analog Optical Transmitter through Systemetic Approach (시스템적 접근을 통한 피드포워드 아날로그 광 송신기의 회로 파라미터 최적화와 W-CDMA 신호의 ACPR 개선)

  • Lee Joon-Jae;Park Sang-Hyun;Yun Young-Seol;Moon Yon-Tae;Choi Young-Wan
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.43 no.5
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    • pp.17-24
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    • 2006
  • The optical feedforward is known as a complicated technique in spite of its superior linearization. Here we optimized the feedforward circuit parameters using a systematic approach for optimum efficiency. A systematic approach was verified by transmission experiments of 2.14 GHz two tones. The compared third order IMD was enhanced by 38 dB for two-tone case. The experimental results for transmission of W-CDMA signals were described. The ACPR was enhanced by 20 dB for 1 W-CDMA carrier and by 16 dB for 3 W-CDMA carriers. Also, noise level was reduced by 7 dB.

Design & Fabrication of a Broadband SiGe HBT Variable Gain Amplifier using a Feedforward Configuration (Feedforward 구조를 이용한 광대역 SiGe HBT 가변 이득 증폭키의 설계 및 제작)

  • Chae, Kyu-Sung;Kim, Chang-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.5A
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    • pp.497-502
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    • 2007
  • Broadband monolithic SiGe HBT variable gain amplifier with a feedforward configuration have been newly developed to improve bandwidth and dB-linearly controlled gain characteristics. The VGA has been implemented in a $0.35-{\mu}m$ BiCMOS process. The VGA achieves a dynamic gain-control range of 19.6 dB and a 3-dB bandwidth of 4 GHz ($4{\sim}8\;GHz$) with the control-voltage range from 0.6 to 2.6 V. The VGA produces a maximum gain of 9.3 dB at 6 GHz and a output power of -3 dBm at 8 GHz.

Compensation of the Nonlinearity of the High-Power Amplifiers with Memory Using a Digital Feedforward Scheme (디지털 피드포워드 방식을 이용한 메모리 효과가 있는 전력 증폭기의 비선형성 보상)

  • Kim, Min;Shin, Ha-Yeon;Eun, Chang-Soo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.49 no.4
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    • pp.9-17
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    • 2012
  • In this paper, we show the memory effect of the high-power amplifiers for wied-band signals, present a compensation method for the nonlinearity combined with memory effect, and analyze its performance. For the modeling and the compensation of the nonlinear high-power amplifier with memory effect, we investigate the Volterra series model, the Wiener model, and the Hammerstein model. As a compensator scheme, we propose a digital feedforward technique. Compared to analog feed-forward scheme, the proposed scheme has better stability and adaptability to the environmental changes. It has a simpler structure than the conventional digital nonlinear compensation schemes. The result of computer simulations using ADS of the Agilent shows that spectral re-growth is suppressed by more than 20 dB, which amounts to at least 10 dB back-off. Considering the compensation performance, implementation complexity, and convergence rate, we could conclude the Wiener model is most suitable for the proposed scheme.

Experiment of Phase Shifter and Voltage Variable Attenuator for Linear Analog Optical Transmitter by Feedforward Compensation (피드포워드 선형화 아날로그 광 송신기를 위한 위상 천이기와 전압 가변 감쇄기의 제작과 측정)

  • Lee Joon-Jae;Park Sang-Hyun;Lee Sang-Bong;Choi Young-Wan
    • 한국정보통신설비학회:학술대회논문집
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    • pp.153-156
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    • 2004
  • 광 전송 마이크로 셀룰라 시스템과 부반송파 다중 송신 시스템 같은 마이크로파 광 전송기술을 이용한 시스템들은 송신기의 비선형성에 의해서 발생하는 많은 왜곡 성분들, 특히 레이저 다이오드에서 발생한 왜곡 성분들에 의해서 많은 성능의 제한을 받는다. 이러한 왜곡 성분들을 제거하기 위해서 광 피드포워드 방식을 이용한 광 송신기를 제안하였다. 제작된 피드포워드 선형화 아날로그 광 송신기는 2.1 GHz 투톤 실험에서 38 dB의 IMD 개선 효과를 보였다. 여기에서 위상 천이기와 전압 가변 감쇄기는 신호 크기 허용오차를 0.1 dB, 위상 허용오차 $1^{\circ}$범위 이내에서 설계하였다. 이를 위해서 세밀한 위상과 크기의 조정이 가능한 위상 천이기와 전압 가변 감쇄기를 제작하였고, 측정한 결과, 전압 가변에 따른 위상 변화량과 크기 변화량은 각각 위상 천이기는 $90^{\circ}$, 전압 가변 감쇄기는 14 dB를 기록하였다.

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Robust Disturbance Suppression Control for AC Servo Motors (AC 서보모터에 대한 견실한 외란억제 제어)

  • Kim, Chang-Hwan
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.4
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    • pp.839-848
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    • 2012
  • In this paper, we propose a robust control scheme of AC servo motors to suppress disturbance torques effectively. The proposed controller consists of both a model based feed-forward controller and a stabilizing feedback controller. The feed-forward controller is designed such that the output of the nominal plant tracks perfectly the reference velocity command with desired dynamic characteristics. The feedback controller stabilizes the overall closed loop system. Furthermore, the feedback controller contains a free function that can be chosen arbitrarily. The free function can be designed so as to achieve both suppression of disturbances and robustness to model uncertainties. In order to illuminate the superior performance of the proposed control scheme to the conventional ones, we present some simulation results.

A New FeedForward(FF) Timing Estimation Technique for High-Speed Transmission of Bursts (고속의 버스트 전송을 위한 새로운 피드포워드 타이밍 추정 기법)

  • 최윤석;조지훈;김응배;차균현
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.12A
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    • pp.1774-1780
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    • 2000
  • 본 논문에서는 TDMA 방식의 고속의 버스트 데이터 전송에서 프리앰블의 오버샘플링 데이터 값을 이용한 새로운 피드포워드 타이밍 추정 기법을 제안한다. 제안된 추정 기법은 검출 오류 분산 값 (DEV : Detection Error Variance) 측면에서 기존의 여러 타이밍 추정기법과 MCRB (Modified Cramer-Rao Bound)와 비교되어 진다. 또한, 제안된 타이밍 추정 기법을 고정 샘플링 클럭과 타이밍 보정기로서 보간 필터를 이용한 심볼 동기 블록을 적용하여 이상적인 경우의 BER과 그 성능을 비교한 결과 이상적인 경우에 비해 성능 저하가 BER이 $10^{-3}$인 지점에서 최대 0.2dB 이내임을 확인하였다.

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Theory of optimal second-order PMD compensation (최적의 2차 편광모드분산 보상에 관한 이론적 고찰)

  • 김상인
    • Korean Journal of Optics and Photonics
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    • v.14 no.6
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    • pp.583-587
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    • 2003
  • In this paper, the optimal performance of optical second-order polarization mode dispersion (PMD) compensation has been investigated theoretically in terms of minimization of the root-mean-square (RMS) pulse broadening. The optimal compensation vector in feedforward-type second-order PMD compensation has been derived, and the RMS pulse broadening factor after the optimal second-order PMD compensation has been analytically calculated. The calculated result has been compared with the previously reported simulation result where numerically optimized feedback scheme was adopted. They are in good agreement, which verifies the validity of the derivation. The investigation in this work will form the basis for the implementation of the feed-forward-type second-order PMD compensation.

A Feed-forward Method for Reducing Current Mismatch in Charge Pumps (전하 펌프의 전류 부정합 감소를 위한 피드포워드 방식)

  • Lee, Jae-Hwan;Jeong, Hang-Geun
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.46 no.1
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    • pp.63-67
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    • 2009
  • Current mismatch in a charge pump causes degradation in spectral purity of the phase locked loops(PLLs), such as reference spurs. The current mismatch can be reduced by increasing the output resistance of the charge pump, as in a cascoded output stage. However as the supply voltage is lowered, it is hard to stack transistors. In this paper, a new method for reducing the current mismatch is proposed. The proposed method is based on a feed-forward compensation for the channel length modulation effect of the output stage. The new method has been demonstrated through simulations on typical $0.18{\mu}m$ CMOS circuits.

Determining the Compensation Voltages for Dynamic Voltage Restorers by use of PQR Instantaneous Power Theory (PQR 순시전력이론에 의한 동적전압보상기의 보상전압 결정)

  • 김효성;이상준;설승기
    • The Transactions of the Korean Institute of Power Electronics
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    • v.8 no.5
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    • pp.442-449
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    • 2003
  • This paper discusses how to generate the reference compensation voltages in Dynamic Voltage Restorers (DVR) by use of PQR instantaneous power theory. Sensed three-phase terminal voltages are transformed to PQR coordinates without time delay. Since the reference voltage in PQR coordinates is a single dc value, the voltage controller for DVRs is simple and easy to design. Proposed control method can be implemented by feedforward controllers or by feedback controllers. This paper verified the theory by a feedforward controller of a DVR with simulation and experiment.