Masaru Kamada

Periodic spline orthonormal bases

On presente un systeme de fonctions constituant une base orthonormee dans un espace de fonctions splines periodiques et convergeant vers le systeme de fonctions orthonormees de Fourier lorsque lordre tend vers linfini

Two-dimensional spline interpolation for image reconstruction

A scheme of two-dimensional (2-D) spline interpolation for image reconstruction is presented. It is aimed to be applied in image data compression. An impulse response derived from 2-D quadratic spline functions is theoretically analysed. Then it is approximated to be a finite-duration one (FIR) for practical implementation. With this scheme, compression rate of greater than 12 is achieved for X-ray left ventricular cineangiogram image data compression.

Design of UWB pulses based on B-splines

The paper discusses the construction of UWB pulses on the basis of B-splines under the following conditions: (i) the B-splines are time-limited piecewise polynomials; (ii) the pulses are rectangular when their order is one and they converge to band-limited functions at the limit that their order tends to infinity; (iii) an analog circuit and a fast digital filter exist for the generation of B-splines. A constrained minimization technique is proposed for designing pulses so as to comply with the FCC spectral mask and satisfy basic requirements for UWB pulses.

A parallel architecture for relaxation operations

Abstract Relaxation method attracts attention as an effective parallel method in image processing and pattern recognition. But their previous parallel implementations are specialized to each application such as image processing at pixel level. The present paper proposes a parallel architecture for a relaxation processor which can be applied to general use. This architecture is based on the round-robin structure of data communication among the processing elements. Its effectiveness is discussed by evaluating its performance when applied to a pattern recognition method.

Window functions represented by B-spline functions

Characteristics of window functions provided by B-spline functions are analyzed in comparison to other known windows. For the same highest-sidelobe level, those windows have a mainlobe bandwidth between those of Gaussian and cos/sup a/ x windows are as good as those of cos/sup a/ x ones in the sidelobe falloff. >

Circuit design of a D/A converter using spline functions

Abstract A D/A converter implementing quadratic spline interpolation is developed. It is different from a conventional D/A converter which consists of a zero-order hold circuit and an analogue low-pass filter. The present D/A converter generates an analogue signal which interpolates an input digital signal by a spline function quickly as well as smoothly. This paper first concerns the theoretical analysis of quadratic spline interpolation, which has characteristics of a low-pass filter. Based on an approximation of the theoretical impulse response of spline interpolation, the practical impulse response is expressed by a piecewise quadratic polynomial, and the D/A converter, using spline functions, is designed by using electronic devices such as operational amplifiers with an R -2 R ladder network, multipliers, adders, shift-registers and so on. This strategy is applicable to LSI implementation of the present D/A converter that can be used in audio equipment, control, measurement, PCM communications, etc.

A quadratic spline function generator

A function generator is developed which purges digital-to-analog (D-A) conversion of phase distortions by replacing both the hold circuit and the analog low-pass filter. This generator implements interpolation of a discrete-time signal by a quadratic spline function which is a smooth piecewise polynomial. Fidelity in the amplitude characteristic of the generator is estimated. It is also proved that the generator is of linear phase. The generator is constructed in the form of a FIR (finite impulse response) digital filter with a time-varying impulse response. Based on the linear phase characteristic, the generator is useful in D-A conversion, especially in audio signal processing applications. >

Spline function approach to digital signal processing

Models of digital signal processing are built on the signal spaces composed of spline functions. It is revealed that the models include and generalize the ideal model on the band-limited signal space, and the conventional model used in practice, with a zero-order or a first-order hold circuit. The models can be implemented accurately using real circuits so far as they are not identical with the ideal model because a spline function can be generated as a piecewise polynomial. Thus the models make it possible to treat signal processing systems which exist between the conventional ideal model and the conventional model used in practice, in design through implementation.

Design of UWB pulses by spline approximation

The present paper discusses a new construction of UWB pulses within the framework of soft-spectrum adaptation. The employed basis functions are B-splines having the following properties: (i) the B-splines are time-limited piecewise polynomials; (ii) the first-order B-splines are rectangular pulses and they converge band-limited functions at the limit that their order tends to infinity; (iii) there is an analog circuit and a fast digital filter for the generation of B-splines. A constrained approximation technique is proposed for adaptively designing pulses so that they approximate target frequency characteristics. At the cost of using eleven shifted B-splines, an example set of four pulses conforming to the FCC spectral mask is obtained.

Effects of ultrasonic components on perceived tone quality

A psychophysical experiment was carried out to study the effects of ultrasonic components on perceived tone qualities. The physical attribute of the experiment was the decay rate of the envelope of the ultrasonic components, and its psychological attributes were the distinctness, brightness, and loudness of tones. It is shown that slower decay tends to make brightness higher and loudness lower. It is concluded that the ultrasonic components must be taken into account in acoustic signal processing as well as auditory analysis.<<ETX>>