• Title/Summary/Keyword: frequency delay

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Robust Pilot-aided Frequency Offset Estimation Scheme for OFDM-based Broadcasting System with Cyclic Delay Diversity

  • Shin, Won-Jae;You, Young-Hwan
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.12
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    • pp.3055-3070
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    • 2013
  • This paper proposes an improved carrier frequency offset (CFO) and sampling frequency offset (SFO) estimation scheme for orthogonal frequency division multiplexing (OFDM) based broadcasting system with cyclic delay diversity (CDD) antenna. By exploiting a periodic nature of channel transfer function, cyclic delay and pilot pattern with a maximum channel power are carefully chosen, which helps to enable a robust estimation of CFO and SFO against the frequency selectivity of the channel. As a performance measure, a closed-form expression for the achievable mean square error of the proposed scheme is derived and is verified through simulations using the parameters of the digital radio mondiale standard. The comparison results show that the proposed frequency estimator is shown to benefit from properly selected delay parameter and pilot pattern, with a performance better than the existing estimator.

X-band Microwave Photonic Filter Using Switch-based Fiber-Optic Delay Lines

  • Jung, Byung-Min
    • Current Optics and Photonics
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    • v.2 no.1
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    • pp.34-38
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    • 2018
  • An X-band microwave photonic (MWP) filter using switch-based fiber-optic delay lines has been proposed and experimentally demonstrated. It is composed of two electro-optic modulators (EOMs) and $2{\times}2$ optical MEMS-switch-based fiber-optic delay lines. By changing time-delay difference and coefficients of each wavelength signal by using fiber-optic delay lines and an electro-optic modulator, respectively, a bandpass filter or a notch filter can be implemented. For an X-band MWP filter with four channel elements, fiber-optic delay lines with the unit time-delay of 50 ps have been experimentally realized and the frequency responses corresponding to the time-delays has been measured. The measured frequency response error at center frequency and the time-delay difference error were 180 MHz at 10 GHz and 3.2 ps, respectively, when the fiber-optic delay line has the time-delay difference of 50 ps.

Efficient Channel Delay Estimation for OFDM Systems over Doubly-Selective Fading Channels

  • Heo, Seo Weon;Lim, Jongtae
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.9
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    • pp.2218-2230
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    • 2012
  • In this paper, we propose an efficient channel delay estimation method for orthogonal frequency-division multiplexing (OFDM) systems, especially over doubly-selective fading channels which are selective in both the symbol time domain and subcarrier frequency domain. For the doubly-selective fading channels in single frequency network (SFN), long and strong echoes exist and thus the conventional discrete Fourier Transform (DFT) based channel delay estimation system often fails to produce the exact channel delay profile. Based on the analysis of the discrete-time frequency response of the channel impulse response (CIR) coefficients in the DFT-based channel delay estimation system, we develop a method to effectively extract the true CIR from the aliased signals by employing a simple narrow-band low-pass filter (NB-LPF). The performance of the proposed system is verified using the COST207 TU6 SFN channel model.

The Design of Variable Delay Line Circuit Using Indirect Frequency Synthesizer (간접 주파수 합성기를 이용한 가변 신호지연 회로 설계)

  • 윤영태;민경일;오승협
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.29A no.2
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    • pp.33-40
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    • 1992
  • The design method of signal delay line system using indirect frequency synthesizer is presented. The variable signal delay line system with 2[nsec] step of delay time at center frequency 60[MHz], bandwidth 500[KHz] and range 5.24-5.81[x10S0-6Tsec] is designed and fabricated. The results were met with good characteristics to be variable delay time of average 2.01[nsec] per step.

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Delay Determination of Cyclic Delay Diversity for Multi-user Scheduling in OFDMA Systems (OFDMA 시스템의 다중 사용자 스케줄링을 위한 순환지연 다이버시티의 지연값 결정)

  • Rim, Min-Joong;Hur, Seong-Ho;Song, Hyun-Joo;Lim, Dae-Woon;Jeong, Byung-Jang;Noh, Tae-Gyun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.3A
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    • pp.248-255
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    • 2008
  • In an OFDMA system the performance of multi-user scheduling in the frequency domain is affected by the frequency selectivity of the channel. If the channel is too flat in the frequency domain, the multi-user scheduling gain might be degraded. On the contrary, if the frequency selectivity is too high and the magnitude of the frequency response severely fluctuates on the allocation bandwidth, it is also hard to get sufficient scheduling gain. For maximizing the multi-user scheduling gain, a cyclic delay diversity technique can be used to adjust the frequency selectivity of the channel. This paper proposes a method to determine the optimal delay value of cyclic delay diversity according to the allocation bandwidth and the channel characteristics.

A Study on Analysis of Time Delay Model Using Autoregressive Method for Mobile Communication Channels (AR 모델을 이용한 이동 통신 채널의 시간 지연 해석기법에 관한 연구)

  • 이형권;류은숙;이종길
    • Proceedings of the IEEK Conference
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    • 1999.06a
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    • pp.29-32
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    • 1999
  • In this study, the time delay model were simulated using the well-known AR model. Frequency response of the time delay model can be obtained by mapping AR model to JTC model in the time domain. That is, from the few measurement data in JTC model, the channel frequency response can be obtained by the estimation of AR model parameters. From this channel frequency response, the time delay model can be obtained using Fourier transformation. To prove the validity of the suggested method, three models of JTC were shown and analyzed.

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A wide range analog synchronous mirror delay adopting the comparator with inherent systematic offset

  • Chae, Jeong-Seok;Young-Jin park;Kim, Daejeong
    • Proceedings of the IEEK Conference
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    • 2000.07a
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    • pp.129-131
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    • 2000
  • A new analog synchronous mirror delay to be used in the wide-bandwidth clocking circuits is proposed to overcome the frequency dependency of the negative-delay values in the conventional analog synchronous mirror delay. The scheme adopts a new dummy-delay compensation technique by adopting the comparator with inherent systematic offset to achieve the enhanced negative-delay range especially prominent at high frequency applications.

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A Study on the Characteristics of MS Delay Blasting Considering Cooperating Charge (협동장약을 고려한 MS 지발 발파 특성 연구)

  • Kang Choo-Won;Kim Jong-In;Park Joung-Bong
    • Explosives and Blasting
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    • v.23 no.3
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    • pp.11-18
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    • 2005
  • The waveform at the blasting pattern using k13 delay electronic detonator depends on the interference of adjacent delay time according to the degree of distance and frequency. The degree of interference affects the size of blasting vibration at a measuring point. This study analyzed the cooperating change characteristics of MS delay blasting separately detonated at intervals of 40m and presented through frequency the delay time design method that is able to reduce the cooperation of blasting vibration at the MS delay blasting.

Design Methodology of the Frequency-Adaptive Negative-Delay Circuit (주파수 적응성을 갖는 부지연 회로의 설계기법)

  • Kim, Dae-Jeong
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.37 no.3
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    • pp.44-54
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    • 2000
  • In this paper, a design methodology for the frequency-adaptive negative-delay circuit which can be implemented in standard CMOS memory process is proposed. The proposed negative-delay circuit which is a basic type of the analog SMD (synchronous mirror delay) measures the time difference between the input clock period and the target negative delay by utilizing analog behavior and repeats it in the next coming cycle. A new technology that compensates the auxiliary delay related with the output clock in the measure stage differentiates the Proposed method from the conventional method that compensates it in the delay-model stage which comes before the measure stage. A wider negative-delay range especially prominent in the high frequency performance than that in the conventional method can be realized through the proposed technology. In order to implement the wide locking range, a new frequency detector and the method for optimizing the bias condition of the analog circuit are suggested. An application example to the clocking circuits of a DDR SDRAM is simulated and demonstrated in a 0.6 ${\mu}{\textrm}{m}$ n-well double-poly double-metal CMOS technology.

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Tunable Composite Right/Left-Handed Delay Line with Large Group Delay for an FMCW Radar Transmitter

  • Park, Yong-Min;Ki, Dong-Wook
    • Journal of electromagnetic engineering and science
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    • v.12 no.2
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    • pp.166-170
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    • 2012
  • This paper presents a tunable composite right/left-handed (CRLH) delay line for a delay line discriminator that linearizes modulated frequency sweep in a frequency modulated continuous wave (FMCW) radar transmitter. The tunable delay line consists of 8 cascaded unit cells with series varactor diodes and shunt inductors. The reverse bias voltage of the varactor diode controlled the group delay through its junction capacitance. The measured results demonstrate a group delay of 8.12 ns and an insertion loss of 4.5 dB at 250 MHz, while a control voltage can be used to adjust the group delay by approximately 15 ns. A group delay per unit cell of approximately 1 ns was obtained, which is very large when compared with previously published results. This group delay can be used effectively in FMCW radar transmitters.