• Title/Summary/Keyword: frequency offset compensation

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Development and Evaluation of Global Fringe Search Software for the Preprocess of Daejoen Correlator (대전 상관기의 전처리를 위한 광역 프린지 탐색 소프트웨어 개발 및 시험)

  • Oh, Se-Jin;Roh, Duk-Gyoo;Yun, Young-Joo;Yeom, Jae-Hwan;Oh, Chung-Sik;Kurayama, Tomoharu;Chung, Dong-Kyu;Jung, Jin-Seung
    • Journal of the Institute of Convergence Signal Processing
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    • v.15 no.4
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    • pp.176-182
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    • 2014
  • This paper introduces the development of global fringe search (GFS) software for preprocessing of Daejeon Correlator. In case of the VLBI observation, a observer conducts the observation for the reference sources with strong and point-like radio stars on schedule in order to confirm the well-observedness of the radio source by the radio telescope. The correlator performs the correlation for the reference sources to detect the fringe completely. We developed the GFS software by calculating the precise delay time between each observatory based on specific observatory. Then, this software calculates the precise delay time by using the delay model (correlator model) of reference source and information of time offset between the Hydrogen Maser frequency standard and GPS (Global Positioning System) clock located in each observatory through the correlation preprocessing. In order to confirm the performance of the developed software, experiments were carried out for the reference sources and target sources observed by the KaVA (KVN and VERA Array). Experimental results show that the GFS software has effectively good performance by finding the precise delay time offset according to the comparison between the compensated delay time offset and one without compensation.

Design and Implementation of Receiver Algorithms for VDL Mode-2 Systems (VDL Mode-2 시스템을 위한 수신 알고리듬 설계 및 구현)

  • Lee, Hui-Soo;Kang, Dong-Hoon;Park, Hyo-Bae;Oh, Wang-Rock
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.10
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    • pp.28-33
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    • 2009
  • In this paper, we propose the receiver algorithms suitable for the VHF (Very High Frequency) digital link mode-2(VDL Mode-2) system. Unlike conventional digital communication systems using the root raised cosine filter as a transmit and receive filter, raised cosine filter is used as a transmit filter in the VDL Mode-2 system. Hence, it is crucial to design and implement the optimum lowpass receive filter by considering inter-symbol interference and noise performance. On the other hand, due to the short preamble pattern, it is crucial to develop an efficient packet detection algorithm for reliable communication link for the VDL Mode-2 system. Also, frequency offset due to the carrier frequency difference between transmitter and receiver and doppler frequency shift must be estimated and compensated for reliable communication. In this paper, the optimum receive filter, packet detection and frequency offset compensation algorithms are proposed and the performance of the VDL system employing the proposed algorithms are evaluated.

A New Simplified Clock Synchronization Algorithm for Indoor Positioning (실내측위를 위한 새로운 클락 동기 방안)

  • Lee, Young-Kyu;Yang, Sung-Hoon;Lee, Seong-Woo;Lee, Chang-Bok;Kim, Young-Beom;Choe, Seong-Su
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.3A
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    • pp.237-246
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    • 2007
  • Clock Synchronization is one of the most basic factors to be considered when we implement an indoor synchronization network for indoor positioning. In this paper, we present a new synchronization algorithm which does not employ time stamps in order to reduce the hardware complexity and data overhead. In addition to that, we describe an algorithm that is designed to compensate the frequency drift giving an serious impact on the synchronization performance. The performance evaluation of the proposed algorithm is achieved by investigating MTIE (Maximum Time Interval Error) values through simulations. In the simulations, the frequency drift values of the practical oscillators are used. From the simulation results, it is investigated that we can achieve the synchronization performance under 10 ns when we use 1 second synchronization interval with 1 ns resolution and TCXOs (Tmperature Compensated Cristal Oscillators) both in the master clock and the slave clock.

The Propose of WAVE System Synchronization Algorithm Based on OFDM (OFDM 기반 WAVE 시스템 동기알고리즘 제안)

  • Oh, Se-Kab;Ryu, Ki-Hee;Kang, Heau-Jo
    • Journal of Advanced Navigation Technology
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    • v.12 no.4
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    • pp.341-349
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    • 2008
  • In this paper the Coefficient Tracking Synchronization Algorithm is proposed for the compensation and the suitability of the fast channel fluctuation OFDM in the WAVE(Wireless Access in Vehicular Environments) system. The in progress of standardization WAVE process, IEEE802.11p's physical layer is considered on the coexistence of fading and Frequency offset of OFDM channel to find the system performance ability and the comparing examination which is taken on the proposed method of Coefficient Tracking Synchronization Algorithm and the performance efficiency. Through the simulation result we also can see that the proposed system improves the channel estimation ability and offers an extra efficiency if compared to the existing method.

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Reduction of Power Ripples in a Doubly Fed Induction Generator Under Current Measurement Errors (DFIG의 전류 측정오차로 인한 발전전력의 리플 저감에 관한 연구)

  • Kim, Young-Il;Kim, Jang-Mok;Hwang, Seon-Hwan;Kim, Chan-Ki;Choy, Young-Do
    • Proceedings of the KIPE Conference
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    • 2007.11a
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    • pp.103-107
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    • 2007
  • In doubly fed induction generators (DFIGs), control of rotor currents allows for adjustable speed operation, active, and reactive power control. This paper presents a DFIG control strategy that enhances the active and reactive power control with controllers that can compensate for the errors caused by current measurement path in the DFIG system. The errors can be divided into two categories: offset and scaling errors. These can induce the speed, active, and reactive power pulsations, which are one and two times the fundamental slip frequency in the DFIG. And these undesirable ripples can do the DFIG harm. In this paper, a new compensation algorithm is proposed. Therefore, the proposed algorithm has several advantages: to implement is easy; it require less computation time; it is robust with regard to the variation of the induction generator parameters. In this paper, a new algorithm is introduced by using the integral of phase currents to measure the current ripples of rotor-side converterin the DFIG system. The experiment results are shown the effectiveness of the proposed method.

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Decoupling of Thrust Force and Levitation Force of Transverse Flux Linear Induction Motor by the Active Compensation of Magnetic force across the Air-Gap (공극력의 능동적 보상을 통한 횡자속 선형 유도 구동기의 추력과 부상력의 비연성화)

  • 정광석;백윤수
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.11
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    • pp.91-98
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    • 2004
  • TFLIM(Transverse Flux Linear Induction Motor), making its closed magnetic path with the direction of the traveling field orthogonal, had been developed to decrease an edge effect of the general induction motor. To control the levitation force and the thrust force on the secondary part of TFLIM independently, the various methodologies have been presented. When we try to achieve the independent control using only the multi-phase inputs assigned in the stator coils as an approach, in which condition we can minimize the coupling effect between two forces\ulcorner In this paper, we show the qualitative influence of a slip frequency, an ac magnitude, a dc offset superposed in the ac power, and a major parameter of TFLIM on the couple through the computer simulation. And to realize the independent motions between levitation and thrust motion without any auxiliary means fur isolation of the secondary part of TFLIM, the decouple compensator is suggested, including the experimental results.

Single Phase PWM Converter For High-Speed Railway Propulsion System Using Discontinuous PWM (불연속 변조 기법을 이용한 고속철도 추진제어장치용 단상 PWM 컨버터)

  • Song, Min-Sup
    • Journal of the Korean Society for Railway
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    • v.20 no.4
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    • pp.448-457
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    • 2017
  • In this paper, for high speed railway propulsion systems, a single phase PWM Converter using discontinuous PWM (DPWM) was investigated. The conventional PWM Converter uses a low frequency modulation index of less than 10 to reduce switching losses due to high power characteristics, which results in low control frequency bandwidth and requires an additional compensation method. To solve these problems, the DPWM method, which is commonly used in three phase PWM Inverters, was adopted to a single phase PWM Converter. The proposed method was easily implemented using offset voltage techniques. Method can improve the control performance by doubling the frequency modulation index for the same switching loss, and can also bring the same dynamic characteristics among switches. Proposed DPWM method was verified by simulation of 100 kW PWM converter.

Synchronization performance optimization using adaptive bandwidth filter and average power controller over DTV system (DTV시스템에서 평균 파워 조절기와 추정 옵셋 변화율에 따른 대역폭 조절 필터를 이용한 동기 성능 최적화)

  • Nam, Wan-Ju;Lee, Sung-Jun;Sohn, Sung-Hwan;Kim, Jae-Moung
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.44 no.5
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    • pp.45-53
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    • 2007
  • To recover transmitted signal perfectly at DTV receiver, we have to acquire carrier frequency synchronization to compensate pilot signal which located in wrong position and rotated phase. Also, we need a symbol timing synchronization to compensate sampling timing error. Conventionally, to synchronize symbol timing, we use Gardner's scheme which used in multi-level signal. Gardner's scheme is well known for its sampling the timing error signal from every symbol and it makes easy to detect and keep timing sync in multi-path channel. In this paper, to discuss the problem when the received power level is out of range and we cannot get synchronization information. With this problem, we use 2 step procedures. First, we put a received signal power compensation block before Garder's timing error detector. Second, adaptive loop filter to get a fast synchronization information and averaging loop filter's output value to reduce the amount of jitter after synchronization in PLL(Phased Locked Loop) circuit which is used to get a carrier frequency synchronization and symbol timing synchronization. Using the averaging value, we can estimate offset. Based on offset changing ratio, we can adapt adaptive loop filter to carrier frequency and symbol timing synchronization circuit.

Design and Verification of IEEE 802.15.4 LR-WPAN 2.4GHz Base-band for Ubiquitous Sensor Network (유비쿼터스 센서 네트워크를 위한 IEEE 802.15.4 LR-WPAN 2.4GHz 베이스 밴드 설계 및 검증)

  • Lee Seung-Yerl;Kim Dong-Sun;Kim Hyun-Sick;Chung Duck-Jin
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.1 s.343
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    • pp.49-56
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    • 2006
  • This paper describes the design and the verification of IEEE 802.15.4 LR-WPAN 2.4GHz Physical layer for Ubiquitous Sensor Network(USN). We designed the Carrier Frequency Offset(CFO) compensation satisfied the frequency tolerance of IEEE 802.15.4 LR-WPAN and the adaptive matched filter that re-setting of the threshold for the symbol synchronization of the various USN environment. The multiplications is reduced 1/16 by this method each other at i, q phases and has 0.5dB performance improvement in detection probability. Proposed baseband system is designed with verilog HDL and implemented using FPGA prototype board.

Design of a computationally efficient frame synchronization scheme for wireless LAN systems (무선랜 시스템을 위한 계산이 간단한 초기 동기부 설계)

  • Cho, Jun-Beom;Lee, Jong-Hyup;Han, Jin_Woo;You, Yeon-Sang;Oh, Hyok-Jun
    • Journal of the Institute of Electronics and Information Engineers
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    • v.49 no.12
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    • pp.64-72
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    • 2012
  • Synchronization including timing recovery, frequency offset compensation, and frame synchronization is most important signal processing block in all wireless/wired communication systems. In most communication systems, synchronization schemes based on training sequences or preambles are used. WLAN standards of 802.11a/g/n released by IEEE are based on OFDM systems. OFDM systems are known to be much more sensitive to frequency and timing synchronization errors than single carrier systems. A loss of orthogonality between the multiplexed subcarriers can result in severe performance degradations. The starting position of the frame and the beginning of the symbol and training symbol can be estimated using correlation methods. Correlation processing functionality is usually complex because of large number of multipliers in implementation especially when the reference signal is non-binary. In this paper, a simple correlation based synchronization scheme is proposed for IEEE 802.11a/g/n systems. Existing property of a periodicity in the training symbols are exploited. Simulation and implementation results show that the proposed method has much smaller complexity without any performance degradation than the existing schemes.