• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.11
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• pp.1299-1310
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• 1992

Recently, digital realizations of timing recovery circuits for digital data transmission are of growing interest. As a result of digital realization of timing recovery circuits, new digital algorithms for timing error detection are required. In this paper, we present a new digital Angular Form(AF) algorithm which can be directly applied to QPSK modulation technique. AF algorithm is basically developed on the concepts of detected angle form and transition logic table. We evaluated the performance of this algorithm by Monte-Carlo simulation method under Gaussian and Impulsive noise environments. From the performance evaluation result, we show that the performance of AF Algorithm is better than that of Gardner in BER, RMS jitter, S-curve.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.419-425
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• 2001

In land mobile communications, multipath fading is one of the key factors which affect the system performance. Some extensive studies have been carried out to improve the degraded performance under this fading channels. The PSAM channel compensation method using channel fading estimation is widely used and TCM is a combined coding and modulation technique that has been shown to provide significant coding gain without increasing the transmission bandwidth. In this paper, we analyze the performance of PSA-TC-8PSK which combines PSAM and TCM over frequency nonselective fading channels. To estimate channel fading, Wiener filter which minimizes error variance is used as compensation method and we analyze the affects on the system performance of the number of filter taps, period of the pilot symbol frame, and the Doppler frequency. In addition, we consider the symbol timing recovery circuit which can be implemented in the full-digital method and analyze the effects of symbol timing error on the system performance.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.6
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• pp.45-53
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• 1996

In this paper, the convergence behavior of timing phase when an adaptive partial response equalizer and decision-directed type of a PLL work together in a digital recording channel is described. The phenomena of getting biased in timing phase when the convergence parameter of an adaptive partial response equalizer and timing recovery constant of a PLL are not selected properly is introduced. The phenomena, occurring due to perturbation of timing phase, are analyzed, by computer simulation and the region of ocnvergence for timing phase is discussed. Also, a method to overcome the phenomena using a variable step-size parameter is described.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.237-244
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• 2003

This paper presents the design of a QPSK/16-QAM downstreams receiver chip. The proposed chip consists of a blind equalizer, a timing recovery block and a carrier recovery block. The blind equalizer uses a DFE sturucture using CMA(Constant Module Algorithm). The symbol timing recovery uses the modified parabolic interpolator. The decision-directed carrier recovery is used to remove the carrier frequency offset, phase offset and phase jitter. The implemented LMDS receiver can support four data rates, 10, 20, 30 and 40 Mbps and can accommodate the symbol rate up to 10 Mbaud. This symbol rate is faster than existing QAM receivers.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.3
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• pp.1-7
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• 2015

PURPOSE: The aim of this study was to investigate the effects of exercise intensity and initial timing on functional recovery following sciatic nerve injury in rats. METHODS: Total of 80 Sprague-Dawley rats was used and randomly divided 6 groups. Under deep anesthesia, the sciatic nerve was nipped by adapted hemostatic tweezers for 30 seconds and the injured nerve was transparent under naked eyes. Acute exercise groups was applied treadmill after sciatic nerve crush injury during 5days with three type intensity. Late exercise groups was also applied treadmill during 5 days with three type intensity after 5 days break. Values of sciatic functional index were measured and analyzed in each group after exercise period. RESULTS: The sciatic functional index values between control groups 1, acute low-intensity group, acute middle-intensity group in acute phase showed statistical significant (p<.05). The sciatic functional index values between control groups 2, late low-intensity group, late middle-intensity group and late high-intensity in late phase showed statistical significant (p<.05). The comparison in acute and late phase, sciatic functional index values of each low-intensity group and each high-intensity group showed statistical significant (p<.05). CONCLUSION: Whether at acute or late phase, treadmill exercise as a therapy obtained beneficial effects of functional recovery and exercise training at low speed is more beneficial effects on the recovery of motor function in acute phase.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8B
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• pp.1436-1444
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• 2000

In this paper, we propose the joint carrier and symbol timing recovery algorithm using repetitive preamble and differential detection for burst modem. The proposed algorithm can estimate the frequency offset and the symbol timing error regardless of the amount of frequency offset, with a high accuracy, even using very short preamble and at low SNR values. The algorithms for continuous phase frequency shift keying (CPFSK) and phase shift keying (PSK) types are developed. Through computer simulations, we compare the proposed algorithm with the existing algorithms on the estimation accuracy in terms of the preamble length, and analyze those bit error rate(BER) performance.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.78-83
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• 1996

A timing recovery circuit of 10 Gbit/s optical receiver is described. The circuit consists of a passive NRZ-to-PRZ circuit, a dielectric resonator filter (DRF) and a narrow band amplifier, which for the first time adopted a temperature compensation technique using the tempareature characteristics of DR. The experimental results showed an output clock phase variation of less than ${\pm}$6 degree over the operating temperature range form 0$^{\circ}C$ to 75$^{\circ}C$ and measured maximum rms jitters of less than 2 phs with the resonance detunings of up to ${\pm}$10 MHz. These experimental results show that the circuit is a suitable for 10 Gbit/s lightwave transmission system.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1819-1822
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• 2002

The authors propose a robust symbol timing recovery (STR) for telephone line modems supporting data rates up to 32 Mbps. The STR is initialized by a start signal from carrier sensor, and the novel method is proposed which resolves the difference between the frequency of the transmitter's clock and the receiver's clock, called baud frequency offset. The proposed method is applied on digital receiver in a 16 frequency diverse quadrature amplitude modulation (FDQAM) system.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.1
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• pp.10-14
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• 1987

Considering transition gating of the input unipolar NRZ signal, the equivalent linear time-invariant model has been derived for the PLL in the timing clock recovery circuits. The magnitude of the alignment and accumulated jitter has been found along a chain of repeaters. For the timing recovery circuit of 90 Mbps optical communication system, the computer simulation shows that, for the first stage of the chain, the alignment jiter and the accumulated jitter are of -5.1766 dB and for the 7-th stage, the alignment jitter and accumulated jitter have the value of -1.0193dB, 4.9053 dB respectively.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1992.10a
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• pp.270-274
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• 1992