摘要:

AbstractA time waveform which is absolutely square integrable and whose Fourier spectrum is identically zero above a certain finite frequency is called a band‐limited waveform. This paper discusses a sampling theorem for a band‐limited waveform based on a set of sampling points. The waveform structure is such that a finite number of sampling points are periodically repeated. The following results are obtained. An interpolation formula which is sufficiently general is established for the sampling theorem of the discussed type. The necessary and sufficient condition is derived for the interpolation function in order that the interpolation formula apply to any band‐limited waveform. By this theorem, required interpolation functions can systematically be determined by the Fourier expansion coefficient, with respect to the angular frequency, of a finite number of two‐variable functions of time and angular frequency, called the generating variable. Then a special case of sampling theorem is considered, where the interpolation filter determined in correspondence to the interpolation function is time‐invariant, deriving the necessary and sufficient condition for the Fourier spectrum of the interpolation function (i.e., the frequency characteristics of the interpolation filter). Some detailed expressions are discussed for the interpolation function, which can easily make the Fourier spectrum continuous

ISSN:8756-6621    

DOI:10.1002/ecja.4400650902

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe effect of parasitic reactances on the original networks as a stage in the qualitative analysis of nonlinear networks is considered. The parasitic reactances considered here are in the form of capacitors connected in parallel with resistors in the branches of a tree and inductors connected in series with the resistors in the branches of a cotree. The first result seen is the effect of the parasitic reactances on the stability of the equilibrium point. It is shown that if the equilibrium point of the original network is strongly stable and matrix (M + Mt) is positive definite, the equilibrium point is asymptotically stable even with parasitic reactances. The second result shows the effect of the parasitic reactances on the eigenvalues of the linearized equation in the vicinity of the equilibrium point. The result shows that the eigenvalues can be classified into those which converge to the eigenvalues of the original network and those which diverge to infinity of the eigenvalues of the matrix ‐M, (λ = lim [a → ∞ sgn {λ(‐M]}), when the parasitic reactances approach zero uniforml

ISSN:8756-6621    

DOI:10.1002/ecja.4400650903

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

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper proposes a construction method for a code (SEC‐MUED code) which corrects single errors and detects multiple unidirectional errors. It is a kind of concatenated code which can be obtained by concatenating the check bits of a Hamming single error correcting code, Berger code, parity code and Berger code with natural number weight assigned to logic value 0 with the information bits. Another method of construction of an SEC‐MUED code has already been proposed by Bose et al. This paper first discusses the construction of the proposed code, proof of the code and construction of the encoder and the decoder. Then a quantitative comparison is made of the proposed code and the code by Berger et al. from the viewpoint of the number of check bits, the number of gates in the signal path of the encoder and decoder, and the complexity of hardware from the implementation viewpoint. As a result, it is shown that the proposed code results in fewer check bits than the code by Bose et al., fewer gates in the encoder and the decoder and less hardware complexity. For example, for information bit length of 64, the number of gates is 69% and 58% of the Bose code in encoding and decoding, respectively, and the hardware complexity is 51% of the Bose code. The proposed code is thus shown to be a more efficient SEC‐MUED

ISSN:8756-6621    

DOI:10.1002/ecja.4400650904

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

年代:1982

数据来源: WILEY

摘要:

AbstractA method for increasing the number of co‐channel users in direct sequence spread spectrum multiple access (SSMA) communication systems is presented. The effect of band limit on SN ratio, autocorrelation, and mutual correlation of PN signals is studied analytically in direct sequence SSMA. The result is that the number of co‐channel users can be increased by 60% with little effect on acquisition of PN signals by setting the bit rate about three times larger than that of usual syst

ISSN:8756-6621    

DOI:10.1002/ecja.4400650905

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

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper evaluates the effect of periodic data transfer from an input processor to internal processors in a distributed‐control, real‐time system. Two models comprising N (≧ 1) call processors (CP) and M (≧ 0) common buffers (CPB) are analyzed and compared. In one model data transfer from the input processor is accepted at any sampling point by the CP subsystem. In the other model data transfer is not allowed if one or more calls are being processed in the CP subsystem at the time of sampling. Steady‐state distributions of calls in the system immediately after the sampling points and maximum traffic to be carried (a0) for the above two models are derived under such conditions as constant sampling period (T), Poisson arrival and negative exponential processing time distribution (mean value h). Furthermore, using such distribution, the distributions of calls in the system at any arbitrary instant are obtained to formulate various performance measures such as the average number of waiting calls in and out of the system and the average waiting time (w). Finally, the following results are shown from some examples of numerical calculation. When T/h is small, although the system with call rejection gives lower performance in terms of a0 and w, it exhibits remarkable behavior in reducing the frequency of data transfer. As T/h which is determined by the sampli

ISSN:8756-6621    

DOI:10.1002/ecja.4400650906

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

年代:1982

数据来源: WILEY

摘要:

AbstractA variety of coding types are proposed to improve the information transmission efficiency for a digital relay and transmission system. Quantitative estimation is required to clarify coding effectiveness with respect to the frequency region of timing waveform sampling characteristics and the time region of intercode interference based on low‐frequency cutoff. Formerly, various calculations were proposed to use the power spectrum for the former purpose and no consideration was given to the latter.This paper explains how to calculate the probability distribution of digital sum variations to estimate pulse transmission code performance in the time region. Since there are instances where the digital sum variations do not reach a desired state as a result of dc component suppression, the transition probability matrix cannot be determined. The transition probability matrix is then determined by introduction of a new parameter called the state vector, whereby the probability distribution can be calculated. Distribution probabilities for the 4B‐3T code digital sum variation are calculated as a practical application of calculation methods. Error rate performances considering these distributions are shown.These calculation methods may permit the estimation of pulse transmission code performance in conjunction with the power spectrum formerly used for the estimation of transmission code performa

ISSN:8756-6621    

DOI:10.1002/ecja.4400650907

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

年代:1982

数据来源: WILEY

摘要:

AbstractIn order to realize a mobile communication system using MSK narrow‐band digital FM modulation, a high‐accuracy and low‐dissipation power IC modulator is needed. In this paper a digital IC double‐balanced mixer, employing a D‐A converter and FET analog switch, is proposed and the design method of a quadrature modulator using this kind of mixer is explained. The spurious level contained in the modulated output signal is analyzed; then the accuracy required of the D‐A converter in order to reduce the spurious level is determined. Next, the relationship is obtained between the upper limit of the carrier frequency of the signal, whose spurious level specification is satisfied by the modulator, and the FET parameters. GaAs FET measurements confirm the analytical results, namely, a quadrature modulator with lower than ‐40 dB spurious level up to about 1 GHz ca

ISSN:8756-6621    

DOI:10.1002/ecja.4400650908

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

年代:1982

数据来源: WILEY

摘要:

AbstractTo introduce digital transmission into mobile communications, various digital FM methods with a modulation index of 0.5, such as TFM and GMSK, have been studied. Stable operation of these transmission systems requires high accuracy in setting the modulation index and carrier frequency in the modulator. This paper describes a quadrature modulator that provides accurate phase control using digital signal processing (DSP). GMSK is used as a modulation scheme, and its characteristics are discussed in detail. In general, the output of a modulator adapting DSP contains deviations from the ideal analog waveforms attributable to sampling, quantization and truncation errors. These errors are superposed as noise on the modulating waves and cause degradation in signal transmission. The relation between the noise spectra and the circuit parameters is first analyzed and the design procedure is then made clear in a form of a flowchart. An example of circuit parameters yielding a ratio of the signal‐to‐noise spectra of 60 dB is given. We fabricated a DPS orthogonal modulator using these parameters and confirmed that the desired modulation characteristics could be obtai

ISSN:8756-6621    

DOI:10.1002/ecja.4400650909

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

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper proposes a new method of circuit construction for the adaptive channel equalizer using frequency sampling filter, together with the result of analysis of its characteristics. In the proposed method, the discrete Fourier transform is applied successively to the received signal and, by adjusting the tap coefficients according to the energy in each DFT coefficient, high‐speed convergence is realized. A discrete Fourier transform using a frequency sampling filter is adopted in the proposed system, whereby an adaptive equalizer with arbitrary number of taps can easily be constructed. From the result obtained by using a simulated sequence, it is seen that the proposed system has the same order of convergence speed with approximately half the number of multiplications and divisions required with the lattice‐type adaptive equalizer. A parallel construction is possible for the adaptive channel equalizer with frequency sampling filter and the method is applicable to existing equipm

ISSN:8756-6621    

DOI:10.1002/ecja.4400650910

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

年代:1982

数据来源: WILEY

摘要:

AbstractIn land mobile communications in a small zone, the same frequency is used repeatedly for efficient use of the frequency spectrum. Therefore, co‐channel interference is easily generated. An analysis is made of the statistical characteristics and error rate performance of a fading 4‐phase DPSK system when multiple channel interference with an arbitrary modulation phase number is present. It is assumed that several services in addition to voice communication will be added in the future. The probability density of two orthogonal outputs from the differential detectors is derived using the characteristic functions, and, based on this quantity, the effects of multiple co‐channel interference on the error rate are studied analytically. The resulting theoretical equation contains not only the autocorrelation of the desired wave but also the correlation of each interference wave. This makes it possible to evaluate the multiple co‐channel interference, the power distributions of each interference and the number of channels. It is assumed that the fading spectra of the desired and interference waves are symmetric with respect to the center fr

ISSN:8756-6621    

DOI:10.1002/ecja.4400650911

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

年代:1982

数据来源: WILEY