• ETRI Journal
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• v.35 no.3
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• pp.397-405
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• 2013

In this paper, two sets of spectrally efficient ultra-wideband (UWB) pulses using zinc and frequency-domain Walsh basis functions are proposed. These signals comply with the Federal Communications Commission (FCC) regulations for UWB indoor communications within the stipulated bandwidth of 3.1 GHz to 10.6 GHz. They also demonstrate high energy spectral efficiency by conforming more closely to the FCC mask than other UWB signals described in the literature. The performance of these pulses under various modulation techniques is discussed in this paper, and the proposed pulses are compared with Gaussian monocycles in terms of spectral efficiency, autocorrelation, crosscorrelation, and bit error rate performance.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.115-119
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• 1987

In this paper the observer design problem in bilinear systems is studied using the Walsh functions as approximating set of functions to find a finite series expansion of the state of bilinear system. A classical Liapnove method, to finding a class of observer feedback matrix, is applied to ensure uniform asymptotic stability of the observation error dynamics. An algorithm is derived for observer state eq. via Walsh function. The basic objective is to develop a computational algorithm for the determination of the coefficients in the expansion. This approach technique gives satisfactory result as well provides precise and effective method for the bilinear observer design problem.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.657-665
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• 1991

Although orthogonal function is introduced in control theory in early 1970's, it is not perfect. Since the concept of integral operator by Chen and Hsiao in mid 1970's, orthogonal function (for example Walsh, Block-pulse, Haar, Laguerre, Legendre, Chebychev etc) has been widely applied In system's analysis and identification, model reduction, state estimation, optimal control, signal processing, image processing, EEG, and ECG etc. The reason why Walsh Functions introduces in control theory is that as integral of Walsh function is also developed in Walsh orthogonal function, if we transfer give system into integral equation and introduce Walsh function. We can know that system's characteristic by algebraical expression. This approach is based on least square error and that result is expressed as computer calculation and partly continuous constant value which is easy to apply. Such a Walsh function has been actively studied in USA, TAIWAN, INDO, CHINA, EUROPE etc and in domestic, author has studied it for 10 years since it was is introduced in 1982. This paper is consider the that author has studied for 10 years and Walsh function's efficiency.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.31 no.8
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• pp.33-38
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• 1982

This paper deals with the simplification of the transfer function in a frequency domain, viz. the integral of the squared errors between the original and the simplified model is minimized and the latter is estimated by the Walsh function. It tries to minimize the errors between the frequency responses of the two functions. This method is compared with the existing method by means of a numercal example. The frequency response of this simplified model approximates closely to that of the original model. The proposed method is simpler in analysis and easier in implementation than the existing methods. Though the Walsh function can be easily generated with the discrete values, it has errors because its zero crossings are not continuous. This method aims at the reduction of the errors in the real parts and the imaginary parts of the two functions by dividing into the more sub-intervals, and selecting the reduced-order model according to the response of the model. As a result, it can be applied for the simplification of higher order functions into lower order functions and for the design of control systems.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.758-760
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• 1995

The purpose of noise cancellation is to estimating signals corrupted by additive noise or interference. In this paper, an adaptive noise canceller is built from a Walsh filter with a new adaptive algorithm. The Walsh filter consists of a Walsh function. Since the Walsh functions are either even or odd functions, the covariance matrix in the tap gain adjustment algorithm can be reduced to a simple form. In this paper, minimization of the mean squre error is accomplished by a proposed adaptive algorithm. The conventional adaptation techniques use a fixed time constant convergence factor by trial and error methods. In this paper, a convergence factor is obtained that is tailored for each adaptive filter coefficient and is updated at each block iteration.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.914-921
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• 1992

In this paper, we introduce a Walsh network and an LMS algorithm, and show how these can be realized as an adaptive equalizer. The Walsh network is built from a set of Walsh and Block pulse functions. In the LMS algorithm, the convergence factor is an important design parameter because it governs stability and convergence speed, which depend on the proper choice of the convergence facotr. The conventional adaptation techniques use a fixed time constant convergence factor by the method of trial and error. In this paper, we propose an optimal method in the choice of the convergence factor. The proposed algorithm depends on the received signal and the output of the Walsh network in real time.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.117-126
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• 2003

This paper proposes a real-time application of Walsh functions which is based on the on-line Walsh transformation and on-line Walsh function's differential operation. In the existing method of orthogonal functions, a major disadvantage is that process signals need to be recorded prior to obtaining their expansions. This paper proposes a novel method of Walsh transformation to overcome this shortcoming. And the proposed method apply to the unknown inputs observer(UIO) design for linear time-invariant dynamical systems

• Proceedings of the KIEE Conference
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• 1984.07a
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• pp.76-80
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• 1984

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.3
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• pp.95-101
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• 1986

This paper describes two methods for analyzing distributed parameter systems (DPS) via Walsh series expansions. Firstly, a Walsh-Galerkin expansion approach technique (WGA) introduced by S.G. Tzafestas. is considered. The method which is based on Galerkin scheme, is well established by using Walsh series. But then, there are some difficulty in finding the proper basic functions at each systems. Secondly, a double Walsh series approach technique (DWA) is developed. The essential feature of DWA propoesed here is that it reduces the analysis problem of DPS to that of solving a set of linear algebraic equation which is extended in double Walsh series.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2620-2623
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• 2000

The standard approach consists of using correlation of orthogonal functions in digital filtering, such as well-known FFT(Fast Fourier Transform) and FWT(Fast Walsh Transform). But it needs much calculations, multiplications and additions. The calculation amount is m $log_2m$ in the general case. Therefore, this requires high speed processors to calculate in real time, which can calculate floating point. This study developed improved fast Walsh transform based on dyadic-ordered fast Walsh transform, then regenerated signal flow graph of improved fast Walsh transform, and used it for digital filtering, and then measured fundamental frequency and harmonics for current and voltage signals of power system.