• Journal of Korea Society of Industrial Information Systems
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• v.20 no.4
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• pp.39-45
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• 2015

In this paper, variable rate CDR(Clock and Data Recovery) circuit adopting blind oversampling architecture is presented. The clock recovery circuit is implemented by using wide range voltage controlled oscillator and band selection method and the data recovery circuit is designed to digital circuit used majority voting method in order to low power and small area. The designed low power variable clock and data recovery is implemented by wide range voltage controlled oscillator and digital data recovery circuit. The designed variable rate CDR is operated from 10 bps to 2 Mbps. The total power consumption is about 4.4mW at 1MHz clock. The supply voltage is 1.2V. The designed die area is $120{\mu}m{\times}75{\mu}m$ and this circuit is fabricated in $0.13{\mu}m$ CMOS process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.823-832
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• 2011

In this paper, an efficient blind carrier frequency offset (CFO) estimation method in orthogonal frequency division multiplexing (OFDM) systems is proposed. In the proposed method, we obtain two time different received OFDM symbols by using both the cyclic prefix and oversampling technique, and a cost function is defined by using the two OFDM symbols. We show that the cost function can be approximately expressed as a cosine function. Using a property of the cosine function, a formular for estimating the CFO is derived. The estimator of the CFO requires three independent cost function values calculated at three different points of frequency offset. The proposed method is very efficient in computational complexity since no searching operation for the minimum cost value is required. The proposed method reduces 97% of the amount of FFT computation, compared with the ML method. Unlike the conventional methods such as the ML method and the MUSIC] method, the accuracy of the proposed method is independent of the searching resolution since the closed form solution exists. The computer simulation shows that the performance of the proposed method is superior to those of the MUSIC and the ML method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10C
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• pp.1001-1009
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• 2009

In this paper, an efficient blind frequency offset estimation method for radio resource saving in orthogonal frequency division multiplexing (OFDM) systems is proposed. In the proposed method, we obtain two time different received OFDM signal blocks by using the cyclic prefix and define the cost function by using the two OFDM signal blocks. We show that the cost function can be approximately expressed as a closed form cosine function. The approximated cosine function can be obtained from three independent cost function values calculated at three different frequency offsets. In the proposed method, the frequency offset can be estimated by calculating a frequency offset minimizing the approximated cosine function without searching all the frequency offset range. Unlike the conventional methods such as MUSIC method, the accuracy of the proposed method is independent of the searching resolution since the closed form solution exists. The computer simulation shows that the performance of the proposed method is superior to those of the MUSIC and the oversampling method.