• Journal of Advanced Navigation Technology
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• v.26 no.1
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• pp.22-28
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• 2022

In order to install ultra wide band and ultra long-haul transmission link based on standard single mode fiber, optical signal distortion due to chromatic dispersion and nonlinear Kerr effect must to be compensated. In this paper, optical link consisted of dispersion management and optical phase conjugation is proposed for compensation of the distorted wavelength division multiplexed (WDM) channels. Dispersion map profile in the proposed dispersion-managed link is configured by periodic repetitive shape, and optical phase conjugator is placed at various position including the midway of total transmission length. It is confirmed from simulation results that when the residual dispersion per span (RDPS) selected in the proposed dispersion-managed link to be large, the compensation of distorted WDM channels in the non-midway OPC system is more improved than the conventional dispersion-managed link.

• Journal of IKEEE
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• v.16 no.3
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• pp.189-196
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• 2012

This paper proposes new phase error compensation method of RVDT encoder in the FFT domain. Phase errors are measured with a small combination of compensation resistors and the changes of first order coefficients of FFT for each resistor are obtained. It is found that the coefficient change is inversely proportional to the inserted resistor. The proposed method takes less time and the size of the table is smaller than previous time domain approaches. In addition, the location of the compensation resistor can be found through axis transformation of the coefficients. Finally, the peak-to-peak phase error was improved to 0.57 which is two times better than previous one.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.719-726
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• 2004

In this paper, compensation characteristics of distorted WDM channel due to both chromatic dispersion and self phase modulation (SPM) is numerically investigated under the assumptions of non-uniformly distributed fiber dispersion, in order to inspect the application of mid-span spectral inversion (MSSI) to any exact transmission links. The MSSI is compensation method used in this approach. This method has an optical phase conjugator (OPC) placed in mid-way of total transmission length to compensate distorted WDM channels. It is confirmed that MSSI will become applicable to long-haul WDM systems by controlling input light power of transmission channels, when the averaged dispersion of both fiber sections with respect OPC was varied and distributed unequally each other. Applying MSSI to long-haul WDM system, it is possible to remove all in-line compensator, consequently it will be expected to reducing system cost.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.450-457
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• 2003

In this paper, we studied the effect of asymmetrical 3rd order IMD of power amplifier due to changes in modulation frequency on IMD cancellation performance. The phase extraction method for determining asymmetric rate for phase distortion of IMD is proposed and the phase difference between lower and upper 3rd order IMD is measured by this method. The phase compensation circuit to decrease the phase difference is also designed and fabricated. From the measurement results using the phase compensation circuit applied to 5 W RF power amplifier fur PCS applications, the 3rd order IMD cancellation performance can be achieved up to 2-tone spacing 1.5 MHz (phase difference within 10$^{\circ}$).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1212-1215
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• 2012

This study describes the accuracy improvement of the estimated angle using phase averaging in phase-comparison monopulse algorithm. In addition, to compensate the time-delay due to the phase averaging, we propose the time-delay compensation algorithm which uses the derivative of the estimated angle. These derivative is calculated by the curve fitting method. Using the real radar interferometer, we have verified that the phase averaging and time-delay compensation algorithms are effective in real-time signal processing application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.959-966
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• 2010

Quantitative ultrasound analysis provides fundamental information of various ultrasound parameters using spectral information of the short-gated radiofrequency(RF) data. Therefore, accurate extraction of spectral information from backscattered RF signal is crucial for further analysis of medical ultrasound parameters. In this paper, we propose two techniques for calculating a more accurate power spectrum which are based on the phase-compensation using the normalized cross-correlation to minimize estimation errors due to phase variations, and the weighted averaging technique to maximize the signal-to-noise ratio(SNR). The simulation results demonstrate that the proposed method estimates better results with 10% smaller estimation variances compared to the conventional methods.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.107-114
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• 2012

In this paper, the concerned existing blind equalizer convergence rate and residual inter-symbol interference using constellation reduced and cost function by separation the real part and an imaginary part, the dual structure CR-CMA(constellation Reduction CMA). The CMA methed compensates amplitude but does no compensate phase, On the other hand, The CMA method compensates both the amplitude and the phase but it has the convergence rate problem, and the MCMA method is a way to solve the phase problem of CMA method compensates both the amplitude and the phase after respectively calculating the real part and imaginary part components. Proposal a new method that the dual structure of CR-CMA, the cost function and error function and respectively calculating the real part and imaginary part components can advantages by improving the CMA and the MCMA algorithms so that the amplitude and phase retrieval and constellation reduce the residual ISI and faster convergence rate and performance is good SER (Symbol Error Ratio) was confirmed by computer simulations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.189-194
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• 2012

The main purpose of reactive power compensation monitoring system is to manage factory electrical installation efficiently by On-Off switching reactive power compensation equipment. The existing reactive power compensation monitoring system is only able to be managed by operator whenever electrical installation needed reactive power. Therefore, it may be possible for propagating the installation's faults when operator make the unexpected mistakes. To overcome the unexpected mistakes, in this paper, the author presents a reactive power compensation monitoring system for factory electrical installation using active database. by using active database production rule, stated system can minimize unexpected mistake and can operate centralized monitoring system efficiently. Test results on the five factory electrical installations show that performance is efficient and robust.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1229-1236
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• 2016

In underwater acoustic multipath channel, a performance of underwater acoustic (UWA) communication systems is affected by dynamic variation of boundary and high temporal and spatial variability of the channel conditions. Time and spatial variations of UWA channel induce a carrier frequency offset (CFO) since a phase and a frequency of received signal mismatch with a transmitting signal. Therefore, a performance of a phase shift keying underwater acoustic communication system is degraded. In this study, we have analyzed a performance of CFO estimation and compensation using a phase code in time and spatial variation channel. A constant amplitude zero autocorrelation (CAZAC) signal is applied as a phase code signal and its performance is evaluated in water tank. The bit error rate of a quadrature phase shift keying (QPSK) system with a phase code is improved about 4 to 10 times better than that without a phase code.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.408-414
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• 2020

The method of overcoming the limitation of optical phase conjugator applied into optical long-haul link for transmitting high capacity wavelength division multiplexed (WDM) channels was investigated. The configuration of optical link was based on dispersion-managed link, in which dispersion compensating fiber inserted into each fiber span with single mode fiber, and optical phase conjugator was added into suitable location of link. The maximum number of fiber spans as a function of the launch power of WDM channels in optical link with optical phase conjugator placed at the proposed location was induced and compared for analyzing the compensation performance of the distorted WDM channels. It was confirmed that the more optical phase conjugator depart from the midway of total transmission length, the less the distorted WDM channels was compensated, however, it was also confirmed that the degradation of compensation can be overcome by the suitable value of residual dispersion per span and by the reasonable choice of fiber span controlling total dispersion accumulated in overall transmission link.