摘要:

AbstractThis paper proposes a nonlinear feedback shift‐register system Rncomposed by combining a memory with an n‐stage shift‐register. A new method for generating a nonlinear binary cyclic shift sequence of length T (1 ≤ T ≤ 2n) which can be generated by the proposed system is discussed using a binary graph Gncorresponding to the state transition of the system Rn. As a first step, the number of sequences is briefly discussed. It is then shown that a sequence of length T that can be generated by the system Rncan also be generated by extending the traditional Scholtz algorithm to determine the non‐degenerate cyclic equivalence classes of length T. Then a method of generating a de Bruijn sequence of length 2nwithout using Boolean function is proposed which corresponds to the Hamilton directed loop in the graph Gn. The method consists of converting the initial n‐th order Hamilton directed loop to another n‐th‐order Hamilton directed loop and requires less memory capacity than the traditional method that determines the next n‐th‐order de Bruijn sequence by utilizing all of the (n‐1)‐th order de Bruijn sequences. The method is effective since the conversion procedure is easy. Because of the greater number of sequences generated and the programmable property of the sequence conversion, the method can be expected to be applicable to spre

ISSN:8756-6621    

DOI:10.1002/ecja.4410630102

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

年代:1980

数据来源: WILEY

摘要:

AbstractIn this paper, a quantized signal is expressed by step functions defined in a finite time interval. The quantized signal has infinite frequency spectra and is distorted when transmitted through band‐limited channels. This paper examines the recovery of the quantized signal from the received signal after passing through an ideal lowpass band‐limited channel. The isolated signal which is zero out of the finite time interval can be recovered. The proposal recovery algorithm is based on an algebraic method and does not contain limiting operat

ISSN:8756-6621    

DOI:10.1002/ecja.4410630103

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe theoretical limit of data compression concerning an analog source is given by Kolmogorov's ϵ‐entropy. But in practical systems in which analog signals are transmitted digitally the sampling and quantizing processes are indispensable. In this paper the ϵ‐entropy of the band‐limited stationary Gaussian signal is obtained and it is shown by use of sampling theorem that it has the same value as in the case of a uniformly sampled signal (stationary Gaussian series). By adding the error due to band‐limiting (sampling error) and the redundancy residue to the quantizing to the ϵ‐entropy and under the restrictions of sampling and quantizing, the relation between mean‐square‐error and transmission rate (speed) can be formulated. By adjusting sampling and quantizing intervals, the data compression limits to such a sys

ISSN:8756-6621    

DOI:10.1002/ecja.4410630104

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

年代:1980

数据来源: WILEY

摘要:

AbstractSequential network analysis is a method of analyzing a network by choosing some independent variables among the unknown variables in the network, expressing the remaining unknown variables sequentially in terms of the independent variable by applying KCL and KVL, and then solving the constraint equations obtained as the result of the sequential process to determine the independent variables. This paper deals with the topological properties of a sequential analysis formulated for an active network. The network topology is represented by current‐ and voltage‐graphs. The set of edges whose unknown variables are chosen as independent variables is called the independent‐edge set (denoted by Eb), the set of edges at which the constraint equations are obtained is called the constraint‐edge set (denoted by Eu), and the set of edges whose unknown variables are expressed in terms of the independent variables is called the covered‐edge set (denoted by Eβ). The sequential step of the analysis proceeds by repeatedly adding to Eβan edge which is current‐dependent and/or voltage‐dependent with respect to Eβ. Thus a sequence of covered‐edge sets is obtained. The conditions for current‐dependent, voltage‐dependent, independent and constraint edges are presented and the duality among them is also clarified. From the sequence of Eβa sequence of EβU Eb‐ Euis obtained. Each of the sets in this sequence specifies the electrical connectivities between Eband Eu. The relation between the edge sets defined above and the structure of 2‐graphs is given. Finally, minimum independent‐edge sets are given for some special types of graphs, and an algorithm to decrease the number of

ISSN:8756-6621    

DOI:10.1002/ecja.4410630105

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe continuous‐phase FSK system is a remarkably beneficial digital modulation and demodulation system due to its good transmission performance over satellite communication circuits and others which has some band restriction elements and nonlinear components. However, no report has been made yet on its practical circuit construction or design method. Here, studies are made on practical circuit structure based on the principle of modulation and demodulation in connection with the binary continuous phase FSK, sometimes called MSK, FFSK, etc., with 0.5 modulation index. Presentation is made for the circuit structures for a modulation system by using the off‐set‐bipolar‐modulation‐and‐synthesis, and for a demodulation system by using the synchronous‐detective‐wave‐coherent‐detection and 2‐steps‐up carrier synchronous system. These are applied appropriately to high‐speed modulation and demodulation over several hundred M bit/s in the radio frequency range in or beyond the microwave frequency. As for the coherent detection, quantitative study is made on impairment figures due to the optimum reception band restriction over the Gaussian transmission system, phase errors of regenerated carriers, and timing discrimination errors. It is concluded that its error characteristics are almost equal to those of the optimum detection system at the BT product of reception, 0.5‐0.6, and its phase error takes a deterioration figure of the two‐phase PSK system. Furthermore, experiments were conducted on modulation and demodulation at the carrier frequency of 1.7 GHz and the data transferring speed of 100 M bit/s to confirm the basic characteristics and theoretical results. The result showed that it could have satisfactory featur

ISSN:8756-6621    

DOI:10.1002/ecja.4410630106

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe symbol rate of an M‐ary DPSK signal, caused largely by inherent high irreducible error in the delay detection system, will be discussed for the case of applying the diversity‐combining reception under high‐speed Rayleigh fading in land mobile radio systems. As for the predetection combining methods of the L‐branch, which comprise selective combining iso‐gain combining and the maximum ratio combining, we will demonstrate anew that both error rates, caused by the envelope fade and random‐FM can be represented entirely by L‐square of the error rate in case of no diversity combiner. Particularly, our analysis centers on improvement of random‐FM. We conclude that the L‐square improvement could be applied to the random‐FM similar to the envelope fade and, further, the optimum combining system which minimizes the random‐FM is also maximum ratio combiner. This report will be helpful in doing comparisons among systems, because it shows that the error rates of M‐ary DPSK with the diversity reception characteristics could be represented in a thorough

ISSN:8756-6621    

DOI:10.1002/ecja.4410630107

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

年代:1980

数据来源: WILEY

摘要:

AbstractIn this paper, the spherical circular array antenna pattern is synthesized and the results are compared with the planar circular array. Since the pattern function is complicated, analysis of pattern syntheses of solid surface arrays such as the spherical array becomes difficult. Herein, pattern synthesis is done numerically by minimizing the mean‐square‐error between the desired and synthesized power patterns using the conjugate gradient method. This method is found to be effective in the pattern synthesis of the spherical array. Calculations show that when elements with sharp patterns are used in the array, phase control is more advantageous in practice than amplitude control. Also shown here is the excitation method by which a circularly polarized pattern along the apex direction can be obtained when turnstile antennas are arrayed conformally on the sphere. With this excitation method, the pattern is synthesized and the axial ratio of polarization for main‐beam scan degrades less for spherical than planar array. Furthermore, for spherical array the axial ratio can be improved by placing the elements on a conducting s

ISSN:8756-6621    

DOI:10.1002/ecja.4410630108

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

年代:1980

数据来源: WILEY

摘要:

AbstractRecently, numerous researches have been made on data compression for digital facsimile transmission and several papers reported on the coding system in which certain signal processing is applied to the local part of the original image before encoding. This facilitates the encoding and improves the data compression rate. This paper proposes a new system which utilizes a signal processing based on the majority principle. This system can be implemented relatively easily by hardware. The image quality reproduced by this system is quite acceptable and can be improved by high‐density sampling. In this paper quantitative analysis is made based on the calculation of entropy and the ideal data compression rate when this signal processing system is used as a preprocessing. A considerable improvement of the data compression rate is shown. In addition, comparison between the proposed system and the existing conventional systems is mad

ISSN:8756-6621    

DOI:10.1002/ecja.4410630109

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

年代:1980

数据来源: WILEY

摘要:

AbstractTo obtain the high performance of a cyrogenic cable envelope employing multilayer vacuum insulations, it is necessary to maintain the presence between layers under 10−2Pa. To investigate the possibility of long‐term high‐vacuum maintenance of a sealed cryogenic cable envelope containing adsorbents, we have cooled a 2‐m cryogenic envelope to a liquid nitrogen temperature and made a degassing analysis and degassing rate measurements. We found that the main degassing component was N2and the degassing rates were at 10‐2to 10‐3Pa. We have also cooled a coconut‐shell charcoal to the liquid nitrogen temperature and obtained the N2adsorption amounts. Based on the above results, we obtained the following conclusion. In a cryogenic cable envelope with an external diameter 70 mm in which Al is used as an outer pipe and the nitrogen shield pipes are stored inside, if we can realize the ultimate pressure below 10‐3Pa, it is possible to have a durability life of over 20 years at a pressure below 10‐2Pa by placing about 1 g of coconut‐shell charcoal per 1 m on the circumference of the liquid n

ISSN:8756-6621    

DOI:10.1002/ecja.4410630110

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe losses of optical fibers may increase during cabling or installation. Such a loss increase may be understood to be due to an exertion of unnecessary external forces on the optical fibers during the above processes because of improper fiber structure. This paper describes the result of the finite element analysis for the stresses applied in cross‐sectional direction upon the core fiber and the unit. It is expected that the degradation of transmission characteristics will be prevented if the stress less than an external force is applied to the fiber cores and unit. As for fiber cores, the 3‐layer cores having buffer layer are considered and then the optimum fiber diameter, buffer layer thickness, etc., are studied. In regards to the unit structure, the test is made for the unit in which a steel wire is located at the center, 6 or 10 core fibers are wound and a binder is applied. Using the above samples, the optimum binder wrapping thickness against the side‐wall pressure and the preferable relation between core fiber diameter and unit diameter are investigated. The core fibers and 6‐core unit are manufactured experimentally and the test is carried out to obtain the relation between the side‐wall pressure and transmission losses. The result shows excellent agreement with theoretical analysis. Thus, we use such a design method to minimize the losses of an opti

ISSN:8756-6621    

DOI:10.1002/ecja.4410630111

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

年代:1980

数据来源: WILEY