• Title/Summary/Keyword: Frequency Offset Compensation

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Effective Compensation of Distorted WDM Signals Related with Frequency Chirp (주파수 �V이 다른 WDM 신호의 효율적 왜곡 보상)

  • Lee, Seong-Real;Yim, Hwang-Bin
    • Journal of Advanced Navigation Technology
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    • v.11 no.4
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    • pp.394-400
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    • 2007
  • We induced the optimal values of optical phase conjugator (OPC) position and dispersion coefficients of fiber sections depending on frequency chirp, which is substantially generated in optical signal by optical modulator and affects the transmission performances. In order to investigate the relation of optimal parameters with various frequency chirp, in this paper, positive(down) chirp, chirp-free and positive(up) chirp are assumed in 40 Gbps ${\times}$ 16 channels WDM transmission system of NRZ format with extinction ratio of 10 dB, which are the worst system parameters in the factor affecting system performance. It is confirmed that the OPC position offset and dispersion offsets between both fiber sections are more increased as frequency chirp become larger. It is also confirmed that the effect of the induced values on the compensation of WDM channels with negative frequency chirp is better than WDM channels with positive frequency chirp.

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A Simultaneous Compensation for the CPE and ICI in the OFDM System (OFDM 시스템에서 CPE와 ICI의 동시보상 방법)

  • Li Ying-Shan;Ryu Heung-Gyoon;Jeong Young-Ho;Hahm Young-Kown
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.12 s.91
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    • pp.1152-1160
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    • 2004
  • OFDM technique was adopted as the standard of IEEE 802.1 la and it has been widely used for wireless LAN, European DVB/DAB system, Korean DMB system. In the standard of IEEE 802.11a the data packet is composed of two parts, preamble and data. Preamble is composed of short pilots and long pilots, which are used for synchronization and estimation of frequency offset and channel. We can also compensate phase noise effect in the transceiver by using above pilots. The phase noise is more complicate than frequency offset and seriously affects system performance. In this paper, we newly propose CPE and ICI simultaneous compensation method to compensate phase noise generated by transceiver oscillator and compare with previous studies. As results, phase noise effect can be significantly compensated by CPE cancellation method, PNS algorithm and our proposed CPE and ICI compensation method. Especially, the proposed CPE and ICI compensation method can achieve the best BER performance compared with original OFDM, CPE cancellation method and PNS algorithm.

A Coherent-based Symbol Detector for 2.45GHz LR-WPAN Receiver (2.45GHz LR-WPAN 수신기를 위한 Coherent 기반의 Symbol Detector)

  • Han Jung-Su;Do Joo-Hyun;Park Tha-Joon;Choi Hyung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.2A
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    • pp.176-186
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    • 2006
  • In this paper, we propose an enhanced symbol detector algorithm for 2.45GHz LR-WPAN(Low-Rate Wireless Personal Area Network) receiver. Because the frequency offset of $\pm$80ppm on 2.45GHz band is recommended in IEEE 802.15.4 LR-WPAN(Low-Rate Wireless Personal Area Network) specification, a symbol detector algorithm having stable operation in the channel environment with large frequency offset is required. For robustness to the frequency offset, non-coherent detection-based symbol detector algorithm is typically applied in the LR-WPAN receiver modem. However, the noncoherent symbol detector has increased performance degradation and hardware complexity due to squaring loss of I/Q squaring operation. Therefore we propose a coherent detection-based symbol detector algorithm with frequency offset compensation using a preamble symbol. The proposed algorithm is more suitable for LR-WPAN receiver aimed at low-cost, low-power and low-complexity than the non-coherent symbol detector, since it can reduce performance degradation due to squaring loss of I/Q squaring operation and implementation complexity. Simulation results show that the proposed algorithm has performance improvement of about 1dB in various channel environments.

Estimation of GPS Holdover Performance with Ladder Algorithm Used for an UFIR Filter (UFIR 필터 Ladder 알고리즘 이용 GPS Holdover 성능 추정)

  • Lee, Young-kyu;Yang, Sung-hoon;Lee, Chang-bok;Heo, Moon-beom
    • Journal of Institute of Control, Robotics and Systems
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    • v.21 no.7
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    • pp.669-676
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    • 2015
  • In this paper, we described the simulation results of the phase offset performance of a clock in holdover mode which was normally operated in GPS Disciplined Oscillator (GPSDO). In the TIE model, we included the time error term caused by environmental temperature variation because one of the most important parameters of clock phase error is the frequency offset and drift caused by the variation of temperature. For the simulation, we employed Maximum Time Interval Error (MTIE) for the performance evaluation when the frequency offset and drift are estimated by using an Unbiased Finite Impulse Response (UFIR) filter with ladder algorithm. We assumed that the noise in the GPS measurement is white Gaussian with zero mean and 1 ns standard deviation, and temperature linearly varies with a slope of $1{^{\circ}C}$ per hour. From the simulation results, the followings were observed. First, with the estimation error of temperature of less than 3 % and the temperature compensation period of less than 900 seconds, the requirement of CDMA2000 phase synchronization under 10 us could be achieved for more than 40,000 seconds holdover time if we employ an OCXO (Oven Controlled Crystal Oscillator) clock. Second, in order to achieve the requirement of LTE-TDD under 1.5 us for more than 10,000 seconds holdover time, below 3 % estimation error and 500 seconds should be retained if a Rubidium clock is adopted.

Frequency Synchronization Algorithm of OFDM System for Fine Frequency Offset Compensation (미세 주파수 옵셋 보상을 위한 OFDM시스템의 주파수 동기 알고리즘)

  • 서재현;한동석;김기범
    • Proceedings of the IEEK Conference
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    • 2000.09a
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    • pp.55-58
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    • 2000
  • 본 논문에서는 제한된 통신 채널의 대역에서 주파수 효율이 높은 OFDM 시스템을 위한 반송파 주파수 동기 알고리즘을 제안한다. OFDM 시스템에서의 반송파 주파수 옵셋은 부반송파 간격의 정수배와 소수배로 나누어진다 소수배 주파수 옵셋이 ± 0.5 근처의 값을 가질 경우에는 정확한 정수배 주파수 옵셋 추정이 어렵고 반송파 동기 PLL이 소수배 주파수 옵셋을 추적하는데 많은 시간이 소요된다. 제안한 알고리즘은 정수배 주파수 옵셋을 제거하기 위해 2개의 심볼 만을 이용하고 다중경로 패널에서도 정확한 정수배 주파수 옵셋의 추정이 가능하다 또한, 소수배 주파수 옵셋이 ± 0.5 근처의 값을 가질 경우 적은 계산량으로 주파수 옵셋을 ± 0.1 이내로 보상할 수 있다.

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A Design of Frequency Synthesizer for T-DMB and Mobile-DTV Applications (T-DMB 및 mobile-DTV 응용을 위한 주파수 합성기의 설계)

  • Moon, Je-Cheol;Moon, Yong
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.1
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    • pp.69-78
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    • 2007
  • A Frequency synthesizer for T-DMB and mobile-DTV applications was designed using $0.18{\mu}m$ CMOS process with 1.8V supply. PMOS transistors were chosen for VCO core to reduce phase noise. The VCO range is 920MHz-2100MHz using switchable inductors, capacitors and varactors. Varactor biases that improve varactor acitance characteristics were minimized as two, and $K_{VCO}$(VCO gain) value was aintained by switchable varactor. Additionally, VCO was designed that VCO gain and the interval of VCO gain were maintained using VCO gain compensation logic. VCO, PFD, CP and LF were verified by Cadence Spectre, and divider was simulated using Matlab Simulink, ModelSim and HSPICE. VCO consumes 10mW power, and is 56.3% tuning range. VCO phase noise is -127dBc/Hz at 1MHz offset for 1.58GHz output frequency. Total power consumption of the frequency synthesizer is 18mW, and lock time is about $140{\mu}s$.

Baseband Receiver Design for Maritime VHF Digital Communications (해양 VHF 디지털 통신을 위한 기저대역 수신기 설계)

  • Kim, Seung-Geun;Yun, Chang-Ho;Kim, Sea-Moon;Lim, Yong-Kon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.8B
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    • pp.1012-1020
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    • 2011
  • In this paper a design of $\pi$/4-DQPSK baseband receiver for the exchange of digital data and e-mail between shore and ship stations and/or among ship stations in the maritime mobile service VHF channels is described. Due to the permitted relatively big frequency instability of local oscillators at the transmitter and the receiver of maritime communication system, the designed baseband receiver should have the capabilities of correct estimation and compensation of the synchronization parameters, such as symbol timing and frequency offset, from the received signal which might include relatively big frequency error. Simulated BER results show that the designed baseband receiver works less than 0.5dB loss under AWGN channel when the normalized frequency offset of the received signal is more then 20%.

A Frequency Offset Compensation Technique for the High Order QAM using a Phase Differential Equation (고차 QAM에 적합한 위상 미분을 이용한 주파수 오차 보정 회로)

  • 박상열;윤태일;조경록
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.41 no.10
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    • pp.27-33
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    • 2004
  • In this paper, we present a carrier recovery circuit using the polarity-decision algorithm that recovers a phase and a frequency error simultaneously. The proposed algorithm catches a frequency error based on a differential of an angular velocity of the signal constellations. Using the differential of a phase error may compensate the frequency error. The symbol prediction method in the proposed algorithm accumulates the symbols, which makes easy to calculate a phase differential. The hardware size of the algerian is small since we use Q data or I only to get phase information. As a result, the algerian shows a pull-in range of normalized frequency error 0.5 under AWGN 15dB.

Study on Integrated for Capacitive Pressure Sensor (용량성 압력센서의 집적화에 관한 연구)

  • 이윤희
    • Journal of the Korean Institute of Telematics and Electronics T
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    • v.35T no.1
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    • pp.48-58
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    • 1998
  • For the purpose of designing novel capacitance pressure sensor, several effects on sensitivity such as parasitic capacitance effects, temperature/thermal drift and leakage current have to be eleiminated. This paper proposed the experimental studies on frequency compensation method by electronic circuit technique, C-V converting method with switched capacitor and C-F converting method with schmitt trigger circuit. The third interface circuit by frequency compensation method is composed to eliminate the drift and leakage component by comparision sensing frequency with reference frequency. The signal transmission is realized by digital signal to minimize the influence of noise and high resolution is obtained by means of increasing the number of digital bits. In the fabricated high performance C-V interface, the offset voltage was not appeared, and in case of voltage source, 4.0V, feed back capacitance, 10㎊, the pressure, 0~10 ㎪, the sensitivity of C-V converter is 28 ㎷/㎪.V, the temperature drift characteristic, 0.051 %F.S./$^{\circ}C$ and C-F converter shows -6.6 Hz/pa, 0.078 %F.S./$^{\circ}C$ respectively, relatively good ones.

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Performance Analysis and Compensation of FH/SC-FDMA System for the High-Speed Communication in Jamming Channel (재밍 채널에서 고속 통신을 위한 주파수 도약 SC-FDMA 통신 시스템의 성능 분석과 보상)

  • Kim, Jang-Su;Jo, Byung-Gak;Baek, Gwang-Hoon;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.6
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    • pp.551-561
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    • 2009
  • FH system is very robust to the jamming interference. OFDM system is very good for the high speed communication system. But, it has high PAPR. SC-FDMA system based on OFT-spread OFDM was proposed to reduce high PAPR. Therefore, in this paper, we like to introduce the FH system into SC-FDMA system, which can be best solution to the jamming hostile environment and for the high power efficiency. Also, OFDM is very sensitive to ICI. Especially, ICI generated by frequency offset and phase noise breaks the orthogonality among sub-carriers, which seriously degrades the system performance. We analyze the performance of the FH SC-FDMA system in the PBJ and MTJ channel. In this paper, the ICI effects caused by phase noise, frequency offset and Doppler effects are analyzed and we like to propose the PNFS algorithm in the equalizer to compensate the ICI influences. Through the computer simulations, we can confirm the performance improvement.