• The Journal of Engineering Research
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• v.2 no.1
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• pp.39-47
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• 1997

This paper presents a single board digital signal processing system which can perform two-dimensional (2-D) digital infinite impulse response (IIR) filtering in realtime. We have developed an architecture to provide not only the necessary computational power but also a balance of the system input/output and computational requirements. The architecture achieves large system throughput by using highly parallel processing at both the system and processor levels. It reduces system data communication requirements significantly by taking advantage of a custom-designed processor and by providing each processor with its own input and ouput channel. After system initialization, almost 100 percent of the time is used for data processing. Data transfers occur concurrently with data processing. The functional level simulation reveals that the system throughput can reach as high as one pixel per system cycle. With only 10MHz clock frequency system, it can implement up to fourth order 2-D IIR filters for video-rate data ($512\times512$ pixels per frame at 30 frames per second). If we increase the system frequency, the system can be used for the preprocessing and postprocessing of video signal of HDTV.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.185-192
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• 2008

The crosstalk is the most serious problem in playing audio signals with more than two speakers. Usually an inverse filter is employed to remove such a Phenomenon. The LNS method, one of most effective design techniques for an inverse filter, has some advantages such as easy implementation and quick computation. However, the inverse filter designed by the LNS method is not easy to adapt immediately for the delivery system change since the pre-measured impulse response is used to design the filter. In this work, we present an adaptive algorithm for the inverse filter design. With the present algorithm. the inverse filter is initially designed by the LNS methods and continuously adjusted to cope with the delivery system changes. To verify the proposed method. some simulations were carried out and the results confirmed that the performance of the crosstalk calculation can be improved in entire frequency range.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.175-185
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• 1998

In this paper, we studied some design methodologies of typical FIR filters based on the peak-error constrained least square criterion which was first introducedd by Adams in 1991. This method is a mixed type of the classical least squared error method(LSM) and the so-called min-max error method (MMM). And by considering both the least squared error as well as the maximum error, the solution, i.e. the impulse response of the filter, can be found only when the restrictions on maximum gain, transition bandwidth, and the squared error are satisfied simultaneously under some trade-off conditions. We used the multiple exchange algorithms for optimization procedure and applied the design methodology to the cases of the multiband filter, the differentiator, and the Hilbert transformer by taking the balance of two design criteria into account. The results show that the peak-error constrained least weighted square error design method(PLEM) is superior in performance to the existing LSM and MMM from both the squared error and the maximum error standpoints. And it is verified that PLEM can be applied to not only the case of simple low pass filter, but also to various types of FIR filters.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.425-435
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• 2016

This paper describes a spread-spectrum clock generation method by utilizing a ${\Delta}{\Sigma}$ digital PLL (DPLL) which is solely based on binary phase detection and does not require a linear time-to-digital converter (TDC) or other linear digital-to-time converter (DTC) circuitry. A 1-bit high-order ${\Delta}{\Sigma}$ modulator and a hybrid finite-impulse response (FIR) filter are employed to mitigate the phase-folding problem caused by the nonlinearity of the bang-bang phase detector (BBPD). The ${\Delta}{\Sigma}$ DPLL employs a two-point modulation technique to further enhance linearity at the turning point of a triangular modulation profile. We also show that the two-point modulation is useful for the BBPLL to improve the spread-spectrum performance by suppressing the frequency deviation at the input of the BBPD, thus reducing the peak phase deviation. Based on the proposed architecture, a 3.2 GHz spread-spectrum clock generator (SSCG) is implemented in 65 nm CMOS. Experimental results show that the proposed SSCG achieves peak power reductions of 18.5 dB and 11 dB with 10 kHz and 100 kHz resolution bandwidths respectively, consuming 6.34 mW from a 1 V supply.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5C
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• pp.452-460
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• 2003

In this paper, an equalizer(RNE) using nonlinear multilayer combining techniques in Bayesian equalizer with a structure of radial basis function network is proposed in order to simplify the structure and enhance the performance of the equalizer(RE) using a radial basis function network. The conventional RE Produces its output using linear combining the outputs of the basis functions in the hidden layer while the proposed RNE produces its output using nonlinear combining the outputs of the basis function in the first hidden layer. The nonlinear combiner is implemented by multilayer perceptrons(MLPs). In addition, as an infinite impulse response structure, the RNE with decision feedback equalizer (RNDFE) is proposed. The proposed equalizer has simpler structure and shows better performance than the conventional RE in terms of bit error probability and mean square error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.370-377
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• 2004

In this paper, we present an adaptive modulation technique for orthogonal frequency division multiplexing (OFDM) for broadband wireless communications. Also, using improved channel prediction, we enhance the performance of adaptive OFDM in high mobility environments. Adaptive modulation technique has been shown to achieve reliable high-rate data transmission over frequency-selective fading channel when OFDM is employed. This scheme requires the accurate channel information between two stations for a better performance. In an outdoor high mobility environment, most of adaptive OFDM systems have to be given the channel information transmitted from the receiver. Even if it is possible, there is some delay. Moreover, the channel impulse response between two stations is very rapidly varied. If the channel information is obsolete at the time of transmission, then poor system performance will result. In order to solve this problem, we propose adaptive OFDM with improved channel predictor. The proposed bit allocation algorithm has a lower complexity and the proposed scheme mitigates the effect of channel delay. Robust approach is less sensitive to outdated channel information. Performance results show that the proposed scheme can achieve considerable performance enhancement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6A
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• pp.464-472
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• 2012

In this paper, we propose a new super-resolution algorithm that uses successive frames by applying the block matching motion estimation algorithm. Usually, single frame super-resolution algorithms are based on probability or discrete wavelet transform (DWT) approach to extract high-frequency components of the input image, but only limited information is available for these algorithms. To solve this problem, various multiple-frame based super-resolution algorithms are proposed. The accuracy of registration between frames is a very important factor for the good performance of an algorithm. We therefore propose an algorithm using 6-Tap FIR filter to increase the accuracy of the image registration with sub-pixel unit. Proposed algorithm shows better performance than other conventional interpolation based algorithms such as nearest neighborhood, bi-linear and bi-cubic methods and results in about the same image quality as DWT based super-resolution algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.65-68
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• 2003

Interconnected power system operation has given rise to the problem of increased fault levels and leads to over stressing of all the components. Use have been made of recently developed high Tc superconductor in devising a superconducting fault current limiter (SFCL) that promises optimum performance in terms of capital cost, size, auto sensing, operational losses, response time and reliability. Recently, research about the application of the SFCL is actively progressing in Korea. To be applied for SFCL practically, the electrical insulation design of SFCL must be developed. Therefore, this paper presents the result of an investigation of the dielectric characteristics of turn-to-turn insulation for SFCL in liquid nitrogen. The dielectric characteristics of turn-to-turn insulation models of SFCL were investigated. We obtained following results. The breakdown voltages increased as the spacer thickness and length increased. And the breakdown voltages of turn-to-turn model without spacer were higher than the breakdown voltages of turn-to-turn model with spacer under impulse as well as AC voltages. The information gathered in this test series should be helpful in the design of liquid nitrogen filled SFCL.

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.285-291
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• 2017

Many methods have been studied to estimate the time delay between incoming signals to two receivers. In the case of the method based on the channel estimation technique, the relative delay between the input signals of the two receivers is estimated as an impulse response of the channel between the two signals. In this case, the characteristic of the channel has sparsity. Most of the existing methods do not take advantage of the channel sparseness. In this paper, we propose a time delay estimation method using BPD (Basis Pursuit Denoising) optimization technique, which is one of the sparse signal optimization methods, in order to utilize the channel sparseness. Compared with the existing GCC (Generalized Cross Correlation) method, adaptive eigen decomposition method and RZA-LMS (Reweighted Zero-Attracting Least Mean Square), the proposed method shows that it can mitigate the threshold phenomenon even under a white Gaussian source, a colored signal source and oceanic mammal sound source.

• KDI Journal of Economic Policy
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• v.36 no.3
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• pp.1-23
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• 2014

This paper has studied the monetary policy in Korea with a time varying VAR model using four key macroeconomic variables. First, inclusion of the exchange rate was a crucial factor in evaluating Korean monetary policy since the monetary policy demonstrated sensitivity to exchange rate movements during the crisis periods of both the Asian financial crisis of 1997 and the global financial crisis of 2008. Second, a specification of the stochastic volatilities in TVP-VAR model is important in explaining excessive movements of all variables in the sample. The overall moderation of variables in 2000s was more or less due to a reduction of the stochastic volatilities but also somewhat due to the macroeconomic fundamental structures captured by impulse response functons. Third, the degree of the monetary policy effectiveness of inflation was mitigated in recent periods but with increased persistence. Lastly, the monetary policy stance towards inflation stabilization has advanced ever since the inflation targeting scheme was adopted. However, there still seems to be a room for improvement in this aspect since the degree of the monetary policy stance towards inflation stabilization was relatively weaker than to output stabilization.