• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.3-8
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• 2016

We propose a modified form of the decision-directed least mean square (DD LMS) algorithm that is widely used in the optimization of self-adaptive equalizers, and show the modified version greatly improves the initial convergence properties of the conventional algorithm. Existing DD LMS regards the difference between a equalizer output and a quantization value for it as an error, and achieves an optimization of the equalizer based on minimizing the mean squared error cost function for the equalizer coefficients. This error generating method is useful for binary signal or a single-level signals, however, in the case of multi-level signals, it is not effective in the initialization of the equalizer. The modified DD LMS solves this problem by modifying the error generation. We verified the usefulness and performance of the modified DD LMS through experiments with multi-level signals under distortions due to intersymbol interference and additive noise.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.5
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• pp.55-67
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• 1982

In this Paper new results relating to the acquisition behavior of a class of first-and secondorder digital phase-locked loops (DPLL) originally proposed by Reddy and Cupta are presented in the absence of noise. It has been found that the number of quantization levels L and the number of phase error states N play important roles in acquisition. For a given L-level quantizer, as N increases, the acquisition time increases, and the lock range decreases. However, the deviation of the steady state phase error decreases in this case. When L increases, the acquisition time decreases, and the lock range increases. However, variation of L affects little for the steady state phase error. In addition, the effects of a loop filter on acquisition have also been considered. One can get smaller acquisition time and larger lock range as the filter parameter value becomes larger. However, deviation of the steady state phase error increases in that case. Analytical results have been verified by computer simulation.

• Journal of Biomedical Engineering Research
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• v.28 no.3
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• pp.429-440
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• 2007

A coded excitation has been studied to improve the performance for ultrasound imaging in term of SNR, imaging frame rate, contrast to tissue ratio, and so forth. However, it requires a complicated arbitrary waveform transmitter for each active channel that is typically composed of a multi-bit Digital-to-Analog Converter (DAC) and a linear power amplifier (LPA). Not only does the LPA increase the cost and size of a transmitter block, but it consumes much power, increasing the system complexity further and causing a heating-up problem. This paper proposes an optimized 1.5bit fourth order sigma-delta modulation technique applicable to design an efficient arbitrary waveform generator with greatly reduced power dissipation and hardware. The proposed SDM can provide a required SQNR with a low over-sampling ratio of 4. To this end, the loop coefficients are optimized to minimize the quantization noise power in signal band while maintaining system stability. In addition, the decision level for the 1.5 bit quantizer is optimized for a given input waveform, which results in the SQNR improvement of more than 5dB. Computer simulation results show that the SQNR of a FM(frequency modulated) signal generated by using the proposed method is about 26dB, and the peak side-lobe level (PSL) of its compressed waveform on receive is -48dB.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.3
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• pp.229-234
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• 2018

Texture is one of the most useful features in classifying and segmenting images. The LBP-based approach previously presented in the literature has been successful in many applications. However, it's theoretical foundation is based only on the difference of pixel values, and consequently it has a number of drawbacks like it performs poorly for the images corrupted with noise, and especially it cannot be used as a multiscale texture descriptor due to the exploding increase of feature vector dimension with increase of the number of neighbor pixels. In this paper, we present a method to address these drawbacks of LBP-based approach. More specifically, our approach quantizes the range of pixels values and construct a 3D histogram which captures the correlative information of pixels. This histogram is used as a texture feature. Several tests with texture images show that the proposed method outperforms the LBP-based approach in the problem of texture classification.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.323-335
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• 1992

In this paper, an adaptive cosine transform coding scheme which incorporate human visual properties into the coding scheme is investigated. Human vision is relatively sensitive to mid-frequency band, and insensitive to very low and very high frequency band. These property was mathematically modelled with MTF(Modulation Transfer Function) through many psychovisual experiment. DCT transforms energy in spatial domain into frequency domain, so can exploit the MTF very efficiently. Another well-known visual characteristics is spatial masking effect that visibility of noise is less in regions of high activity than in regions of low activity. Proposed coding scheme imploys quantization matrix which represent the properties of these spatial frequency response of human vision, and adaptively quality of an image. To compute the activity index of an image block, simple operation is performed in spatial domain, and according to activity index. block of low activity region is more exactly quantized relatively than that of high activity region. Results showed that, at low bit rate, the subjective quality of the reconstructed images by proposed coding scheme is acceptible than that of coding scheme without HVS properties.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.7 s.337
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• pp.21-26
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• 2005

An area efficient, low power switch-matrix semidigital FIR reconstruction filter for delta-sigma D/A converter is proposed. Filter coefficients are quantified to 7-bit and 7 current sources that correspond to each coefficient bit are used. The proposed semidigital FIR reconstruction filter is designed in a 0.25 um CMOS process and incorporates 1.5 mm$^{2}$ of active area and a power consumption is 3.8 mW at 2.5 V supply. The number of switching transistors is 1419 at 205 filter order. Simulation results show that the filter output has a dynamic range of 104 dB and 84 dB attenuation of out-of-band quantization noise.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1165-1172
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• 2006

The rapid progress of the software has enabled individuals to copy and remark digital contents, which was only done by professionals. As a solution for the problems, contents producer needs to have certification and inspection of its contents and hold the proprietary right. A fragile watermarking method is able to detect the distortion and damage of watermarked image, but the watermark is also fragile on standardized image compression. That is the problem of fragile watermarking technique. We propose semi-fragile watermarking technique that is robust in the image processing such as JPEG compression used on computer, but it is fragile on the addition of noise and other attacks. In the proposed method, we can generate the watermarks of an image from the relationship between two block coefficients, also the generated watermark is inserted into insensible part of HVS(Human Visual System) after processing DCT(Discrete Cosine Transform) and using quantization. As a result, on the spatial domain, high detection of distortion has been possible even in slight changes, and could detect the corrupted blocks on image. Therefore, it is simple to judge the pixels at which some location has been changed in the space.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.101-108
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• 1998

An efficient approach to recognize occluded objects is to detect a number of essential features on the boundary of the unknown shape. The salient points including corner points, tangential points and inflection points are detected by the relation of neighboring pixels of each pixel on the boundaries. Corner points are usually detected in the curvature function and tangential points and inflection points are detected by median filtering the curvature function to avoid the effect of quantization noise as corner points is not sufficient to represent an object with lines and arcs. Then, these salient points are used as features for object matching. Discrete Hopfield Neural Network is used for object matching. Experimental results show that the matching result using salient points is better than those of using corner points only when an object consists of lines and arcs.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.51-59
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• 2009

This paper presents the design of continuous-time sigma-delta modulator for acoustic sensor. The feedforward structure without summing block is used to reduce power consumption of sigma-delta modulator. A high-linearity active-RC filter is used to improve resolution of sigma-delta modulator. Excess loop delay problem in conventional continuous-time sigma-delta modulators is solved by our proposed architecture. A low power, high resolution fourth-order continuous-time sigma-delta modulator with 1-bit quantization was realized in a 0.13-${\mu}m$ 1-Poly 8-metal CMOS technology, with a core area of $0.58\;mm^2$. Simulation results show that the modulator achieves 91.3-dB SNR over a 25-kHz signal bandwidth with an oversampling ratio of 64, while dissipating $290{\mu}W$ from a 3.3-V supply.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.2
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• pp.11-19
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• 2010

Most of deblocking filters assumes that the block boundaries are accurately known and the coding information like quantization parameters are available. In some applications such as commercial television, however, many external video inputs without known block boundary and coding information arc given. If a decompressed video sequence heavily degraded with blocking artifacts is given through the external video port, it is absolutely necessary to detect block boundaries and control the strength of deblocking filtering by analysing the given images. This paper presents an efficient method to find the block boundaries and estimate the strength of the blocking artifacts without the knowledge of coding information. In addition, the confidence of the estimated blocking artifact information is also evaluated to control the adaptive deblocking filter robustly. Experiment results show that the estimated block boundary locations and strength relative strength and confidence information are practically good enough to reduce the blocking artifacts without prior knowledge.