摘要:

AbstractThe wideband speech signal spectrum is mainly distributed within the low‐frequency band. Subband coding and adaptive predictive coding have been proposed as low‐bit rate speech coding algorithms to take advantage of this property. This paper theoretically clarifies the improvement in signal‐to‐quantization noise ratio when these two bit‐rate reduction techniques are used at the same time and quantitatively analyzes the speech signal spectrum distribution. It also proposes a wideband speech coding algorithm which encodes 7‐kHz‐band speech signals at 64 kb/s, the same encoding bit rate as that of the conventional companding PCM. Through computer simulation the subjective quality is evaluated and the effectiveness of the algor

ISSN:8756-6621    

DOI:10.1002/ecja.4410690901

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper presents a new “ordering” based suboptimal vector quantization, the successive approximation vector quantization (SAVQ). It is found that the SAVQ algorithm can be reduced to the bit arrangement mapping from vector to scalar followed by the scalar quantization. Therefore the SAVQ requires no calculation of distortion. However, the tree search vector quantization (TSVQ), another suboptimal VQ, does require calculation of distortion. This allows the real time vector quantizer to be implemented with significantly less hardware complexity than TSVQ. For the source with exponential density, the simulation results demonstrate that SAVQ provides the mean‐squared‐error equal to or less than that obtained

ISSN:8756-6621    

DOI:10.1002/ecja.4410690902

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

年代:1986

数据来源: WILEY

摘要:

AbstractNewton's method is well known for finding the fixed point of the Poincaré mapping for steady‐state analysis of nonlinear oscillatory circuits. However, in practice, quadratic convergence of this method is not ensured due to the discretization error of the numrical integration and the errors of the approximate solutions for nonlinear equations which are solved at each time‐step of the numerical integration. This paper proposes a new method for the steady‐state analysis of nonlinear nonautonomous and autonomous systems which takes account of the numerical integration error stated above. In this method, the system of equations which includes a Poincaré mapping is discretized and reexpressed is a system of finite difference equations to which an iterative decomposition method is applied. Although this approach is essentially equivalent to the conventional Newton method based on the Poincaré mapping, it has the advantages that the Jacobian matrix can always be computed exactly for an arbitrary time‐steplength and that the local quadratic convergence of the algorithm is guaranteed. Considering these advantages, this paper also proposes a strategy to improve the computational efficiency of the algorithm in which initially, a large time step is used to find a rough solution which is then used as the starting value in the subsequent Newton iteration. Numerical examples are given to verify the relevant theorems and to show the effectiveness of the proposed

ISSN:8756-6621    

DOI:10.1002/ecja.4410690903

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper discusses the measure of information for the event using the probability theory by Dempster and Shafer. By providing various kinds of information to the event containing an ambiguity, the ambiguity is gradually decreased to define the event in a clearer way. The combination rule by Dempster is most suited to represent the combination of information. This paper shows first that several representations can be made for Dempster's combination rule. Then using the upper and lower probabilities defined by the basic probability of the event, the upper and lower information measures are defined, followed by the discussion of their properties. The lower probability of a set (event) is defined as the sum of basic probabilities of all subsets in the set, and the upper probability is defined as the sum of basic probabilities of all sets which contain an element of the set. Thus, the upper and lower information measures can be interpreted as the measures of information concerning the message with ambiguity. Finally, several examples are discussed, determining the information measure for the message containing ambiguity.

ISSN:8756-6621    

DOI:10.1002/ecja.4410690904

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

年代:1986

数据来源: WILEY

摘要:

AbstractWith the development of microcomputers and signal processors in recent years, A/D and D/A converters have increased their importance as analog/digital interfacing circuits. In the past, various types of A/D and D/A converters have been proposed and implemented for practical use. However, they do not necessarily satisfy the requirements for miniaturization, power saving, and low cost. In this paper we have proposed two A/D converters and one D/A converter which utilize the characteristics of a switched capacitor amplifier with switched capacitor bias and load circuits. Their principle, circuit configurations and experimental results are presented. In the proposed A/D and D/A converters only one active element is used. Also the capacitor is much smaller than in the conventional converters. Therefore, the proposed converters are advantageous as an analog/digital interfacing circuit with respect to miniaturization, power saving, and low cost. Experimentally, 5‐bit A/D and D/A converters were built with discrete components and tested. The obtained result confirmed their proper application with a linearity of ± 1/2 L

ISSN:8756-6621    

DOI:10.1002/ecja.4410690905

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn the (k, n) threshold scheme, the informationXis partitioned and coded into subinformation. If anyksubinformation is obtained amongnsubinformation, the original informationXcan be recovered completely. However, no information can be obtained at all concerningXfrom any (k– 1) subinformation. Thus, the (k, n) threshold scheme is suited to the distributed storage or transmission of information. On the other hand, each subinformation requires the same number of bits as the original informationX, which is very inefficient from the viewpoint of the coding efficiency. This paper extends the (k, n) threshold scheme and proposes the (k, L, n) threshold scheme. In the proposed scheme, the original information can be recovered completely from anyksubinformation, but no information concerningXis obtained at all from any (k–L) subinformation. From any (k–t) subinformation (1 ≤t≤L– 1), the information obtained forXcontains the ambiguity of (t/L)H(X). In (k, L, n) scheme, the bit‐length of each subinformation is 1/Lof the informationX, which is a coding with very high efficiency. This paper presents a construction method for (k, L, n) threshold scheme, together with the discussion of its ch

ISSN:8756-6621    

DOI:10.1002/ecja.4410690906

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper describes standardization of wavelengths in wavelength‐division‐multiplexing transmission for optical subscriber loop systems. First we estimate the minimum channel spacing for both the short and long wavelength regions considering such system requirements as transmission distance, transmission signals and future trend of optical components (e.g., optical source, optical multi/demultiplexer, optical connector and optical fiber) and select eight wavelengths in the short wavelength region (0.75, 0.77, 0.79, 0.81, 0.83, 0.85, 0.87 and 0.89 μm) and eight wavelengths in the long wavelength region (1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40 and 1.45 μm). Then, considering presently required transmission signals and the present state of the art of optical sources and optical components, it is concluded that the use of two wavelengths in the short wavelength region (0.81 and 0.89 μm) and two in the long wavelength region (1.2 and 1.3 μm) will suffice for the time being, and that with the required technological advances, necessary wavelengths will be developed and used from among the 16 wave

ISSN:8756-6621    

DOI:10.1002/ecja.4410690907

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe power inversion adaptive array proposed by Compton differs from other adaptive arrays in that it does not require any information on the desired signal. However, there is a sudden reduction in the ratio of signal to interference and noise (SINR) at the output terminal when the relative bandwidth of the interference signal exceeds 5%. In this paper the elements are arranged in a circular arc and a formula is proposed for microprocessor determination of the element weight from the covariance between the element inputs. It is shown that the decrease in SINR is kept below 3 dB even when the relative bandwidth of the interference is as large as 50%. In Method 1 of the circular arc arrangement an element is placed at the center of the circle and in Type 2 no element is placed at the center. Wideband elimination of the interference can be achieved with the arrival angle orthogonal to the line connecting two arbitrary elements. The element arrangements are studied with a low level of redundancy for this ideal angle of arrival. It is shown that a system without redundancy can be realized with a 4‐element array of Method

ISSN:8756-6621    

DOI:10.1002/ecja.4410690908

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper aims at the total design of synchronizing clock phase quality in a master‐slave synchronization network and studies the clock path phase errors. In master‐slave synchronization, reference clock distribution paths are a major source of phase errors. It is useful to examine the phase errors using Time Interval Error (TIE), specified in units of time. In this paper, the TIE of clock paths containing multiplexers, digital transmission lines and digital synchronous terminals is analyzed. Then measurements taken for multiplexers are presented by varying a stuffing ratio. Field data taken for a 7‐link clock path, the longest effective link path in Japan, shows that in practice a TIE of less than 100 ns over a 102– 103s measurement period is measured, which agrees well with theoretic

ISSN:8756-6621    

DOI:10.1002/ecja.4410690909

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper presents theoretical relations between transmission characteristic and increase of effective binary access channels in existing synchronized digital multiplex communication systems such as FDM and TDM to absorb traffic burst when connected to digital channels whose capacity is larger than their traffic capacity. At BER = 103 in noise‐free transmission and without off‐set of the demodulator, a 10 percent increase of digital channels is obtained by using a discrete amplitude level of 4 (2‐bit alternating binary encoding) and 14 percent increase by the amplitude level of 8 (3‐bit alternating binary encoding). At BER = 10‐4 with transmission S/N of 30 dB and demodulator off‐set of ‐23 dB, the increase of channels is 5 percent both by the amplitude levels of 4 and 8. The case of amplitude level of 4 is most preferable considering the relation between BER and the increase of ac

ISSN:8756-6621    

DOI:10.1002/ecja.4410690910

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

年代:1986

数据来源: WILEY