摘要:

AbstractThis paper discusses a method to improve the resolution of an analog‐to‐digital (A‐D) converter to detect differences less than 1 LSB (least significant bit) in the input signal. Resolution is improved by superposing dither on the input signal and averaging over many measurements. The theory and experimental verification for this method are described.This analysis calculates numerically the expectation value of the result of A‐D conversion and the expectation value of the variance, with the dither superposed on the input signal. The results show that for larger amplitude of dither, the expectation value of A‐D conversion comes closer to the real value, and the expectation value of the variance becomes larger.The relation between the amplitude of dither and the improvement of resolution is calculated as a function of the number of measurements. For example, when the number of measurements is 100 and the amplitude of dither is 0.4 LSB, the resolution can be improved to 0.05 LSB.This analysis is verified experimentally by using a white noise generator as a dither source, dc voltage standard as a signal source, and a transient recorder as an A‐

ISSN:8756-6621    

DOI:10.1002/ecja.4410641202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThe sliding DFT algorithm is a technique for determining the DFT coefficients for time‐series samples. The conventional sliding DFT circuit used in the frequency‐sampling filter, however, is recursive and has an instability problem because of the accumulation of errors in the feedback path. A new sliding DFT circuit is proposed which is also of recursive type but does not accumulate errors. Its behavior is analyzed in detail. The circuit proposed is relatively simple and can easily be translated into hardware. It is also shown that a sliding Hadamard transform circuit is easily constructed, and the design of a sequence sampling filter is sh

ISSN:8756-6621    

DOI:10.1002/ecja.4410641203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThe degree of reliability is analyzed for the case where the preventive maintenance is applied to a parallel redundant system with two mutually related and repairable units. The bivariate exponential distribution (BVE) is introduced to describe the failure time distribution of two units that are not independent and mutually related. The reliability analysis of a repairable two‐unit parallel redundant system assuming a BVE failure distribution has already been reported. In this report, two methods of preventive maintenance are considered in the system with the BVE failure distribution. (1) Mutually related preventive maintenance is applied to the system only when both units obey the BVE distribution in failure time distribution. (2) Simultaneous preventive maintenance is applied to two units at prescheduled times. In the reliability analysis, the limiting availability of the system is calculated by using an extended regeneration point method in Markov renewal processes (MRP). In numerical examples, actual figures are assigned to each distribution and the time ratio of preventive maintenance for the two units is defined. Then the relationship between variations of the time ratios and the limiting availability is show

ISSN:8756-6621    

DOI:10.1002/ecja.4410641204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractWith the number theory transform it is possible to perform a high‐speed convolution operation without multiplication and without numerical errors. For this reason, applications of the number theory transform to FIR digital filters have drawn attention. However, when the number theory transform is applied to digital filters, the operating word length becomes extremely large to prevent overflow at the output and this becomes a serious problem in actual hardware implementation. A method is proposed for expanding the dynamic range of the input and output in which the higher order difference of the impulse response is made another impulse response. It is shown that the proposed technique can greatly expand the input and output dynamic ranges. The method can also be combined with other techniques to improve its effectivenes

ISSN:8756-6621    

DOI:10.1002/ecja.4410641205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractArithmetic operations on a finite field are now often used in error control or digital signal processing and there is need for a more practical method for carrying out these operations. A detailed discussion is given of the arithmetic operations, with the elements of finite field represented as powers. In other words, the addition table which can be constructed is of the order of 1/(2 · m) of the Zech logarithmic table. A detailed discussion is given of its construction algorithm, and a practical arithmetic operation algorithm using the table is presented. The size of the addition table is estimated and a storage scheme is considered for the addition table over a finite field with index 2. It is also shown that the addition table is easily set up on a computer

ISSN:8756-6621    

DOI:10.1002/ecja.4410641206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper introduces the twisted coordinate system and presents theoretical investigations of the existence of EM fields whose polarization plane rotates helically. First, concrete expressions for vector operations are derived and the vector wave equations in homogeneous and isotropic media are given in terms of covariant and contravariant components. Then the EM wave whose polarization plane rotates with the coordinate axis is investigated. The results show that propagating rotating polarized wave fields do not exist if the electric field has only a single twisted coordinate component and that the TEM wave exists only as circular‐polarized plane wave fields. By combining two circular‐polarized waves propagating in opposite directions, parallel electric and magnetic fields exist. The Hertz vectors suitable for this type of coordinate are derived and general equations for TE and TM mode EM fields are obtai

ISSN:8756-6621    

DOI:10.1002/ecja.4410641207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractIn the interpolative coding method, the pixels constituting the image are divided into “transmitted points” and “interpolated points,” and the former only are transmitted to the receiving end from the sending end. The latter are reconstructed by interpolation at the receiving end. Commonly, the original image values have been used for the transmitted point values as they are, or, the original image values have been properly lowpass filtered for the transmitted point values. However, judging from the entire image transmission system, the problem of how to determine the transmission point values at the sending end is closely related to the interpolation method at the receiving end.In this paper, we propose a pre‐compensative interpolation coding method such that given the interpolation method at the receiving end, the transmission point values at the sending end are determined so that the sum of the squared error between the transmitted points and interpolated points is minimized. We introduce two kinds of pre‐compensative interpolation coding methods for the case where the interpolation at the receiving end is linear, that is, a locally pre‐compensative interpolation coding method and a globally pre‐compensative interpolation coding method. According to a simulation using a standard image, the following effects have been recognized: the improvement of the SN ratio in comparison with existing simple linear interpolation which uses the original image values as the transmitted point values, and the decrease of the image quality degradation which seems to be

ISSN:8756-6621    

DOI:10.1002/ecja.4410641208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractIn the conventional analysis of the phased array, the array structure is considered infinite. This kind of approach is effective only for the investigation of the pattern from the centrally located elements and is not applicable for edge elements. In this paper, the edge effect of the dipole phased array is studied by introducing virtual generators in the analysis. The analysis method is applied for the calculation of the element pattern, current distribution, and active impedance of edge elements.

ISSN:8756-6621    

DOI:10.1002/ecja.4410641209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper deals with numerical analysis of the reflection of electromagnetic waves from a conductive plate with periodic dielectric distribution. Analysis is based on the Fourier series expansion method (FEM) whereby (i) the EM fields in a periodic inhomogeneous medium are Fourier‐expanded and from this the propagation constant and modal function are found by an eigenvalue equation and (ii) the reflection coefficient is obtained from the boundary conditions between the inhomogeneous medium and free space. Previously, when the dielectric constant E(x) was Fourier‐expanded but the expansion coefficients did not converge absolutely, this method would be abandoned and another method would be sought. In this paper, even in this case, we show that the FEM is still effective. If ε(x) is expressed as ε(x) / ε0= q(x)/r(x) and the expansion coefficient of q(x) and r(x) can be obtained analytically, it can be shown that there is no need for numerical integration. As a result, the applicability of the FEM for systematic numerical analyses of periodic and inhomogeneous media is greatly extended. Actual numerical analysis is applied to the cases of square, cubic and exponential distributions of the dielectric constant toward avoidance of reflections of the periodic, inhomogeneous layers of the medium. Also, this method may be applied to optical grating pr

ISSN:8756-6621    

DOI:10.1002/ecja.4410641210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY

摘要:

AbstractElectromagnetic (EM) noise is radiated when electric trains run along the Shinkansen and the VHF content causes TV receiver jamming. Currently a shared receiving method is put into practice for anti‐jamming. The jammed area extends several hundred meters to each side of the railroad, but if the noise can be reduced by 6 dB the area will be narrowed by a factor of 3 to 4. Earlier noise reduction methods were: improvement of pantograph structure, change of rubbing plate material and use of ferrite in key parts of the pantograph. However the problem on both sides of the railroad remains difficult to solve. In this paper we propose that conducting nets be installed on the supporting poles of the trolley wires. With a net three meters in width, calculation shows that the noise at 150 MHz can be reduced by 6 dB. In the calculation the noise source is taken to be a point source and the field is determined by superposing the waves diffracted from the upper and lower edges of the nets. The calculated results have been verified by experiments with a 1/70 reduced scale mode

ISSN:8756-6621    

DOI:10.1002/ecja.4410641211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1981

数据来源: WILEY