摘要:

AbstractThis paper proposes a new construction method of extended codes based on BCH code using a Fourier transform over a finite field. This method applies encoding to a so‐called “tail” which is added for extension and, furthermore, repeats similar encoding to the encoded tail. the constructed codes based on primitive BCH codes generally are excellent in the point of code rate (= number of information symbols/code length) and it is clarified through examples that some of them improve the lower bounds of the maximum code rate. Since the extended codes constructed by this method can generally be considered over an extended field of one degree lower order compared with the shortened codes with the same code length, the number of multiplications needed for syndrome‐calculation in decoding can be reduced to about a fourth. Moreover, it is shown that when the code is constructed by this method, the fast Fourier transform algorithm can be applied to a wider range of code lengths than before in syndrome‐ca

ISSN:8756-6621    

DOI:10.1002/ecja.4400660802

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

年代:1983

数据来源: WILEY

摘要:

AbstractIn transmission systems of modulated data or picture signals, bandpass filters are required with symmetrical amplitude and delay characteristics around their own center frequencies on an arithmetic frequency scale. In variable attenuation equalizers, etc., band‐elimination filters are required with arithmetically symmetrical stopband amplitude characteristics around the center frequency. This paper proposes frequency transformations to make an analog bandpass filter and a band‐elimination filter (with geometrically symmetrical amplitude characteristics around the center frequencies that are obtained through reactance frequency transformation from analog lowpass filters) into a digital bandpass filter and a band‐elimination filter with arithmetically symmetrical amplitude characteristics. This transformation maps the positive imaginary axis and the negative real axis of analog frequency S to the real axis and the upper half of the unit circle on the z‐plane. the interval on the unit circle of the z‐plane mapping of the positive imaginary axis of the S‐plane is designed to cover the specified frequency region. This is done by controlling the locations of geometrically symmetrical two frequency points around the center frequency of bandpass (band‐elimination) filter by adjusting the parameters of lowpass‐bandpass (band‐elimination) transformation. Some design exampl

ISSN:8756-6621    

DOI:10.1002/ecja.4400660803

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

年代:1983

数据来源: WILEY

摘要:

AbstractThis paper discusses the time‐correlation function of the chaotic solution (socalled chaos) of the one‐dimensional nonlinear equation. the simplest method to obtain the solution is to calculate directly the trajectory, which, however, requires a large computation time to obtain statistics with sufficient accuracy. From such a viewpoint, recently it was proposed to utilize the eigenfunction expansion of the correlation function by the eigenfunction of Perron‐Frobenius integral operator PT. However, this eigenfunction expansion produces an infinite series and the calculation of the eigenfunction itself is difficult. This makes the method impractical. This paper defines the pseudo‐Boyarsky mapping, which is a kind of piecewise‐linear mapping. It is shown that for this class of mappings, the operator PT. can be replaced by a finite‐dimenisonal matrix P on an appropriately constructed functional space. By this result, the obtained correlation function can be represented by a finite series. the eigen‐function needed in the calculation of the correlation function can be determined by operations in l

ISSN:8756-6621    

DOI:10.1002/ecja.4400660804

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

年代:1983

数据来源: WILEY

摘要:

AbstractSingle byte (= b bits) error‐correcting and double byte error‐detecting (SbEC‐DbED) codes are useful for semiconductor memory systems with memory chips of b‐bit output per one address. In this paper, codes with information length k up to k = 128 bit for 2 b 8 are derived experimentally using a computer. As a result, codes with longer code lengths than before are obtained. In particular, as for the codes of b = 2 and k = 64, 12 check bits were required in the conventional codes, but the codes requiring only 10 check bits are derived by experiments and are an excellent result from a practical viewpoint too. In the derivation, each column in an H matrix of the code is regarded as an element in a Galois field GF (qr) where q = 2b(b is the number of bits in a byte) and r is the number of check bytes. to obtain codes with large code length, as many elements as possible are selected in GF(qr) satisfying the code condition. Here, a subset in a GF(qr) whose elements are linearly independent, is used to select the columns of the H matrix. Moreover, all the elements of GF(qr) arising as operation results in the derivation process can be in correspondence to the elements of the subset. Consequently, the objective sets are restricted and the derivation through computer experiments is faci

ISSN:8756-6621    

DOI:10.1002/ecja.4400660805

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

年代:1983

数据来源: WILEY

摘要:

AbstractDepending on the parameter values various kinds of bifurcations can be produced in a nonlinear system. Although there have been many studies made on the bifurcations of fixed points, many problems remain unsolved for bifurcations of invariant closed curves. On the other hand, it has recently been noted that deterministic systems sometimes exhibit chaotic solutions. This phenomenon is called chaos, which is becoming one of the important problems in engineering. However, little attenuation has been devoted to bifurcation and chaos in sampled data systems. This paper discusses the relation between the bifurcation, chaos and sampling period in a sampled data system with dead zone. As the first step, the fold bifurcation set and the range of existence for chaos are determined for a one‐dimensional sampled data system. Then the fold bifurcation set and the Hopf bifurcation set are determined for a two‐dimensional sampled data system. It is verified by numerical experiment that transition of the invariant closed curve to chaos by Hopf bifurcation is closely related to the stable and unstable manifolds of saddle‐type fixed

ISSN:8756-6621    

DOI:10.1002/ecja.4400660806

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe receiving behavior of a window mechanism, an important function of flow control in packet switching computer networks, is modeled by a 2‐stage tandem queueing system with total capacity limitation. In queueing analysis, it is difficult to obtain analytical solutions for such a limited queueing system because the local balancing equations do not hold. This paper proposes two approximate analytical methods utilizing the state transition rate diagram structure: simple analysis method and heuristic approximation method. the former gives the upper and lower bounds of the steady‐state probabilities of the given system, the latter obtains the approximate analytical solutions directly. the properties of the two methods, applicability and the relation between the two methods, are clarified from numerical and simulated results and it is shown that the two analysis methods are effective approximation methods. Throughput, average system size and average waiting time are calculated and it is shown that the two approximation methods are very useful for evaluating the performance measures of the window mechan

ISSN:8756-6621    

DOI:10.1002/ecja.4400660807

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

年代:1983

数据来源: WILEY

摘要:

AbstractIn this paper, a frame synchronization characteristic and its improvement in degraded bit‐error‐rate conditions (BER = 10−2± 10−1) and in the presence of burst errors, are discussed. For the pattern matching type of frame synchronization, an algorithm of two‐frame‐search‐and‐check, in conjunction with the conventional method of allowable bit errors in the detection of sync word, is studied. By regarding the number of allowable errors as design freedom, this paper clarifies the optimum design condition in two‐frame‐search‐and‐check algorithm and its characteristic improvement effect, in comparison with the conventional algorithm. By using this method, the number of backward protection stages is increased equivalently, the holding time when BER is degraded is improved and the allowable burst length is increased by 102‐ 105times. Also, in the reframing characteristic, since the holding of false synchronization is decreased, the reframing time is shortened and the design freedom for the number of al

ISSN:8756-6621    

DOI:10.1002/ecja.4400660808

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

年代:1983

数据来源: WILEY

摘要:

AbstractThis paper presents a numerical analysis for the scattering of horizontally polarized waves incident on a conducting rectangular cylinder (cross‐section = 2a × 2b) by using the point matching method (PMM). the order of simultaneous equations in the analysis has been reduced to one‐fourth by using the four‐phase symmetrical coordinate method. This has led to a high accuracy of the analysis even for large values of kp0(k: wavenumber, p0= √a2+ b2. This paper presents also the numerical results of scattering electromagnetic fields by a conducting rectangular cylinder lying on a flat ground (x‐z plane) which are derived from the two components of four‐phase symmetrical coordinate analysis satisfying the boundary conditions on the x‐z plane. to obtain our numerical results, we did the following: (1) made comparison with the results and discussions of others on similarities and discrepancies among those results, which have led to the justification of PMM, (2) presentation of high‐precision results by PMM for the problems which were analyzed with poor accuracy by other researchers; (3) presentation of scattered far‐field patterns by the skyscraper “Sunshine‐60” in Tokyo as an example for a large value of kp0= 84.73, comparing vertical polarization. Lastly, a simple method is proposed to calculate approximate scattering fields for large values of kp0the applicability limit if shown for this approximation method by comparing those results with the

ISSN:8756-6621    

DOI:10.1002/ecja.4400660809

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

年代:1983

数据来源: WILEY

摘要:

AbstractIn the microwave wireless power transmission in the solar power satellite system, it is important to obtain design data on the power transmission. Major consideration is given to the effect of microwaves on the electromagnetic environment, such as biological bodies, communication channel, and ionosphere. In this paper, the aperture illumination of the transmitting antenna for the microwave beam transmission is assumed that maximizes the transmission efficiency, and the maximum receivable power. the power density outside the receiving antenna, with consideration given to the electromagnetic environment, is studied. Under the maximum transmission efficiency, the maximum power density outside the receiving antenna is at the edge of the receiving antenna. Hence, the receivable power is obtained when the power density at the center of the receiving antenna and that outside it are restricted below certain values as an environmental constraint. Thus, a design method can be given for a microwave wireless power transmission system. A fast converging numerical method is given for deriving the aperture illumination for maximum transmission efficiency.

ISSN:8756-6621    

DOI:10.1002/ecja.4400660810

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

年代:1983

数据来源: WILEY

摘要:

AbstractDiffraction problem of an E‐polarized plane wave by a thick slit in a lossy dielectric slab is analyzed. the Fourier transform technique is used to formulate the problem and the Wiener‐Hopf method is utilized to solve it. Our numerical results revealed the following:(1)maximum values of diffracted fields are not located in the incident direction or in the direction of coherent reflection;(2)amplitudes of total electric fields behind the slab are not necessarily maximum in the incident direction;(3)in the case of a thin slab the maximum amplitudes of diffracted fields are proportional to |1 ‐ T| at the back of the slab and to |R| in front, where T is the transmission coefficient and R is the reflection coefficient for an infinitely long slab;(4)when a slab becomes more lossy, diffracted fields converge asymptotically to some constant v

ISSN:8756-6621    

DOI:10.1002/ecja.4400660811

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

年代:1983

数据来源: WILEY