bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance characteristics of QPSK signal passing nonlinear channel in digital ship earth station system
Authors: Okinaka Hideo 
Published: July 2007

AbstractThis paper presents the out‐of‐band emission characteristics and the BER performance of the QPSK signal passing a class‐C power amplifier in a ship earth station transmitter and compares them with those of the QPSK signal passing a solid‐state linear power amplifier operating near saturation. The study is made mainly by computer simulation. The results show that the BER performance degradation for the class‐C power amplifier is approximately 0.9 dB at BER of 10‐6 with appropriate filtering when adjacent‐channel interference is absent. This BER performance is almost the same as that for the linear power amplifier. However, the class‐C power amplifier generates a higher level of out‐of‐band emission over a wide frequency range than the linear power amplifier, which in an SCPC system degrades the BER performance of adjacent channels. It is quantitatively shown that larger carrier spacing should be adopted for class‐C power amplifiers than for linear power amplifiers to cope with this degradation. Finally, the feasibility of using a class‐C power amplifier for the ship earth station transmitter is discussed for the digital system employing 36‐kbps QPSK which has been developed for possible INMARSAT application. It is concluded that system operation with 50‐kHz carrier spacing is feasible, while operation with 25‐kHz carrier spacing is infeasible when class‐C transmitters are used. On the other hand, system operation with 25‐kHz carrier spacings is feasible when linear transmitters are used.
A neural network model for the discrimination of spatio‐temporal patterns
Authors: Futami Ryoko , Hoshimiya Nozomu 
Published: July 2007

AbstractA neural network model which learns to discriminate spatio‐temporal patterns is proposed. This model is composed of pulse‐type neuron models taking account of its realization with hardware. Input pulse trains whose dynamic features are emphasized by ON‐type neurons propagate through the uniform neural chains and are then fed to plastic neuron models which are laterally interconnected with suitable inhibitory/excitatory weights. After iterative training steps, various phases of input spatio‐temporal patterns are reproduced on the spatial patterns of synaptic weights, and plastic neurons are organized to form some functional groups that respond only to some voice features.
An improved Ziv‐lempel coding scheme for universal source coding
Authors: Yokoo Hidetoshi 
Published: July 2007

AbstractThis paper proposes a universal information source code (improved ZL code) based on the Ziv‐Lempel (ZL) incremental parsing algorithm. It is known that a ZL code is asymptotically optimum for a stationary ergodic information source, although it does not utilize the source structure. Its convergence, however, is very slow and it cannot provide efficient compression for an input string of limited length. This paper considers the redundancy of ZL code, which is the reason for the slow convergence. In order to eliminate the redundancy a coding scheme is presented in which only the substring obtained by incremental parsing is used in the next stage. When the substrings of the incremental parsing are separately coded the improved ZL code obtained by the proposed scheme is the least redundant in the sense that the mean code length for the substrings is minimized. In the coding a data structure called modified ZL tree is introduced and its properties discussed together with two coding algorithms based on that structure. The coding is actually performed for the output string from a memory‐less binary source and binary Markov source. It is shown that sufficient compression is realized for a binary code string length of 103 to 104, indicating the possibility as a practical data compression algorithm.
Consideration on a nonlinear multicommodity flow problem in a packet switching network
Authors: Kurosawa Kaoru , Hasebe Takayuki 
Published: July 2007

AbstractIn a packet switching network it is important to route traffic flow so as to minimize message delay. This problem is formulated as a multicommodity flow problem with a nonlinear objective function and it is solved by the steepest descent method. It is also necessary to control the traffic demand at each node so that the total message delay is below a certain level. This paper presents an algorithm to obtain the region vectors consisting of traffic demand at each node which can be transmitted simultaneously under the given delay time. Despite its importance this region has not been adequately considered. A nonlinear T‐cut condition is introduced by which the region is obtained. This paper is a nonlinear extension of the authors' recent work.
Proximity feed microstrip antenna
Authors: Haishi Katsuyuki , Itoh Kiyohiko 
Published: July 2007

AbstractThe proximity feed microstrip antenna (PMA) fed via a gap enables switching of the polarization with a simple operation of opening or shorting the end of the feed. However, since the PMA is coupled electromagnetically with the feed line printed on the same surface as the antenna, the effect of the feed line on the antenna characteristics is expected. In this paper, the full‐wave analysis developed by Itoh et al. is used for the analysis of the antenna system including the feed line. In this method, Galerkin's method is used in the Fourier transform domain. The effects of the feed line on the resonant frequencies and the radiation patterns of the PMA are investigated. The application of the PMA to a circularly polarized antenna has been tried and actual generations of circular polarizations have been confirmed. The effect of the feed line on the circular polarization characteristics (axial ratio) has been studied.
An interactive fuzzy satisficing method for multiobjective nonlinear programming problems with fuzzy parameters
Authors: Sakawa Masatoshi , Yano Hitoshi 
Published: July 2007

AbstractThe fuzziness induced in the decision making in the actual system in general, comprises fuzziness in the formulation of the problem and that in the judgments of the decision maker (DM) as a human being. This paper proposes an interactive fuzzy satisficing method, which takes into consideration the fuzziness in problem formulation as well as that in the judgments of DM. The multiobjective nonlinear programming problem containing fuzzy parameters is transformed into the α ‐multiobjective nonlinear programming problem. After determining the fuzzy goal of DM for each objective function by eliciting the membership function, the following reference values are set: the fuzziness index α of DM for the fuzzy parameter; and the reference membership values, which are reference for the membership functions. For the specified α and the reference membership values, the corresponding augmented minimax problem is solved, and DM is supplied with the α‐Pareto optimal, together with the trade‐off ratios among membership functions and the trade‐off ratios between α and the membership functions. Obtaining the result, the DM takes the information concerning current α‐Pareto optimal solution and the trade‐off ratios into consideration, and respond by updating the reference membership values and the value of α if necessary. In this way the satisficing solution finally is derived for DM, thereby ensuring the α‐Pareto optimality. This is the proposed interactive fuzzy satisficing method. The interactive process is demonstrated for a numerical example by the interactive computer program.
A signal‐flow graph representation for switched‐capacitor networks and its application to SC circuit design
Authors: Kaneko Mineo , Onoda Mahoki 
Published: July 2007

AbstractThe n‐phase switched‐capacitor (SC) circuit operates by taking successively connection configurations. Consequently, even if the same edge voltage is considered, it takes n different kinds of voltages in general in a period. This makes it difficult to describe the operation of the SC circuit. Although several methods have already been proposed for representing the operation of the SC circuit, the representation by equivalent active RC circuit, which is presently used most widely, cannot provide a clear‐cut description of this essential point. From such a viewpoint, this paper first derives the primitive signal‐flow graph (SFG) representation for adequate representation of the SC circuit, which is formulated based on the common tree in the SC circuit. Then the simplified SFG representation is derived which is obtained by simplifying the representation, eliminating the cotree‐edge variables from the primitive SFG representation. The simplified SFG representation is a network representation, in which only the tree‐edge voltage and the tree‐edge stored‐charge in each phase are used as the variable‐node. It can adequately provide an intuitively clear representation of the relation between the variables in each phase and the relation between the timing of the switch connection and the operation of the circuit. The condition for the structure of SFG is derived, which corresponds to Hasler's structure condition in order that the stray capacitance does not affect the operation. By this method, the problem of constructing an SC circuit insensitive to the stray capacitance is reduced to the problem of constructing an SFG satisfying a certain condition.
A consideration in wave optics on the partial reflected wave by a Gaussian beam propagating through a square‐law medium
Authors: Kozaki Shogo , Ohki Makoto 
Published: July 2007

AbstractThis paper describes the numerical results and derivation of the partial reflected waves from a square‐law medium in which a Gaussian beam is incident. First the WKB solution for the wave equation in the square‐law medium is presented along with approximate solution for the first, second and third reflected waves. The investigated partial reflected waves can not be found by means of the WKB solution. An approximate expression for the partial reflected waves between two reflected beams is derived by Bremmer series. It is found that the partial reflected waves do not depend on the spot size of the beam and are basically proportional to the gradient of the permittivity. The theoretical results are in good agreement with the experimental results.
A formula for mean queue length of GI1 GI2/GI1 GI2/1 preemptive‐resume priority queues
Authors: Takahashi Haruhisa , Akimaru Haruo 
Published: July 2007

AbstractIt is difficult to perform a strict analysis for the GI1GI2/G1G2 single‐device preemptive‐resume priority queue, in which the arrival follows the renewal process and the processing time follows the general distribution. This paper discusses this kind of system and proposes a simple and accurate approximation for the mean queue length which coincides with the strict solution when the arrival is a Poisson process. The proposed approximation is derived by the moment analysis based on the two‐dimensional jump‐diffusion approximation. Furthermore, the diffusion coefficient is corrected based on the Pollaczek‐Khinchin formula for the M/G/1 queue system to improve the accuracy of approximation. The formula is extended to the case of n‐class priority customers. Although the proposed approximation is essentially for the heavy traffic situation, by comparing the result with the strict solutions for GI M/M1M2/1 system and simulations it is shown that the approximation has a sufficient accuracy also for medium and light traffic situations. The result is also compared with other approximations for M GI/G1G2/1 and GI1GI2/G1G2/1 systems, and it is indicated that the proposed approximation has a better accuracy than the past approximations.
Folded antenna loaded with a dipole for circular polarization
Authors: Nakamura Takashi , Abeta Takehiro , Yokokawa Senji 
Published: July 2007

AbstractAnalysis and design of a circularly polarized antenna made of a folded antenna loaded orthogonally with a dipole of an appropriate length is presented here. This antenna is developed in recognition that a folded antenna includes the characteristics of a transmission line. It is a simple single‐feed antenna without a power divider and a phase shifter commonly used in a conventional crossed‐dipole antenna. Making use of the fact that the current distribution can be decomposed into the balanced and unbalanced modes, one can derive the equivalent circuit and the equivalent crossed dipoles of the present antenna. The circular polarization condition is derived on effective lengths and impedances of dipoles. Based on investigation of this condition, a circularly polarized antenna has actually been designed and the characteristics of axial ratio and radiation pattern have been obtained. It is found that this antenna has few structural restrictions. Among them, element length is somewhat arbitrary. Validity of the theoretical results has been experimentally confirmed.
An IIR‐type echo canceller using a two‐channel lattice filter
Authors: Kurosawa Kaoru , Chao Jinhui , Tsujii Shigeo 
Published: July 2007

AbstractIn echo cancellation, the length of impulse response of an echo path to be estimated exceeds a few thousand. Therefore, instead of conventional FIR‐type algorithms, IIR‐type adaptive algorithms which can identify it with fewer parameters is desired. In the IIR case, the stability test of the estimated transfer function is important.This paper presents an IIR‐type identification method which utilizes a 2‐channel lattice filter. The method estimates the unknown transfer function and tests its stability with O(n) operations per iteration where n is the number of the filter coefficients. The estimated transfer function always converges to the optimum solution when the input sequences can be modeled as an autoregressive (AR) process. An optimum approximate solution of an arbitrary order less than that of the estimated system can be obtained at the same time.
Crosstalk attenuation characteristics of unshielded flat cables considering earth effect
Authors: Kuwaki Nobuo , Sato Masaji 
Published: July 2007

AbstractAt present, flat cables for the under‐carpet use have a shielded structure to improve crosstalk characteristics. However, unshielded cables are advantageous when a very thin structure is desired. This paper is concerned with crosstalk attenuation characteristics of unshielded flat cables laid in close proximity to the ground. In this case not only the direct crosstalk due to electrostatic and magnetic couplings between conductors but also the indirect crosstalk via a path along the line to the ground must be considered. By defining the unbalance angle θ to express the degree of impedance unbalance to the ground, the coupling impedance between the longitudinal line and the real line was calculated and formulas to calculate the impedance unbalance to ground and the indirect crosstalk attenuation were derived under the assumption of a perfect conductor for the ground. Next, using these formulas the indirect crosstalk attenuation and the impedance unbalance to ground were studied as functions of the cable structure and actual cable layout such as the pair distance and the ground separation. As the result, the indirect crosstalk can not be improved by increasing the pair distance, and the impedance unbalance to ground is approximately proportional to the crosstalk attenuation. The results obtained are useful in the crosstalk design of unshielded flat cables.
A parallel architecture for recursive least square method
Authors: Hashimoto Koichi , Kimura Hidenori 
Published: July 2007

AbstractRecent developments in computer technology have enabled the real‐time treatment of signal processing with a large amount of computation which had been considered to be impossible. Moreover, with the development of LSI technology, it has become possible to speed up the execution of the algorithms by parallel computing hardware.This paper discusses a parallel architecture for the recursive least square method of system identification fitted for VLSI. If n is the order of system to be identified, the complexity T(n) required for updating the estimate at each measurement is Ts(n) = o(n2), using a single serial processor. However, it can be reduced to Tp(n) = o(n) by using the architecture consisting of (2n + 6) elementary processors and a set of delay units. Moreover, we discuss a method to speed up p‐time updates from Ts(n, p) = o(n2p) to TM(n, p) = o(n + p) using o(np) elementary processors by vectorizing the measurements.
Performance of matched filter detection for multiphase DPSK signal in satellite‐aircraft multipath channel
Authors: Miyagaki Yoshiya , Konishi Kenichi 
Published: July 2007

AbstractData transmission between a satellite and an aircraft is investigated in the case of a multiphase DPSK system operating in the L‐band. The error rate characteristics of matched filter detection are analyzed exactly on the basis of a multipath model consisting of a direct path wave and a relatively delayed, high‐speed, diffuse‐path Rayleigh wave due to reflection at the Earth's surface. On the basis of this model, concrete error rate (Pe) computations are performed in the case of 4‐phase DPSK (symbol rate 1/Ts) as a function of the Doppler spread (BD) and average relative delay (T) of the reflected wave. Considering the influence of varying duration of the reflected wave, the results show that the error rate Pe is maximum (worst case) for BDTs ≒ 0.40 independently of the powers of the direct wave, reflected wave and noise. Furthermore, in the range BDTs ⩽ 0.17 the diffusion wave can be treated as an AC vector. Next considering the influence of the relative delay of the reflected wave, the value of Pe is given for the 16 cases of phase difference in the delay range 0 ≦ T ≦ Ts and it is shown that the effect of relative delay is negligible for T/Ts ⩽ 1/40 and that the minimum average error rate (best case) is obtained for τ/Ts ≒ 1/5.
Experiment on searching for electromagnetic wave sources by using a synthetic aperture technique
Authors: Nagasawa Yoji , Kikuchi Jun'Ichi , Sato Risaburo 
Published: July 2007

AbstractTo control unwanted electromagnetic waves, it is important to estimate accurately the location of the electromagnetic source nearby. Based on the synthetic aperture technique and the signal processing algorithm of the spatial Fourier transform, the location of the source within a planar space of 10 wavelength square has been performed with an electromagnetic source model. It is confirmed experimentally that a satisfactory search of the source is possible using Mills' cross method. A parallel twin wire is used as the electromagnetic source model. Different types of discontinuities are placed along the transmission line and the electromagnetic wave is forced to radiate to create a source. In practice, 300 or 400 MHz is selected and 21 measurement points are selected along the x and y axes with each half‐wavelength spacing. The error of locating the measurement points is the cause of the wave source estimation error. It is demonstrated that the algorithm used here is rather insensitive to these errors.
Reflecting characteristics of anisotropic rubber sheets and measurement of complex permittivity tensor
Authors: Hashimoto Osamu , Shimizu Yasutaka 
Published: July 2007

AbstractIt is well known that rubber sheets mixed with carbon particles or carbon fiber usually exhibit large surface anisotropy due to the rolling process employed in fabrication. The use of such materials for special microwave applications requires measurement of the complex permittivity tensors. However, no reliable method for this purpose in such lossy anisotropic materials has been established. In this paper the reflection loss of anisotropic sheet materials is measured and a method for obtaining complex permittivity tensors from the experimental results is given. That is, the frequency characteristics of the reflection loss are measured for various polarization directions of incident waves at the sheet materials and each element of the tensors including nondiagonal ones can be estimated by the least squares method using these data. As a result of study of the principal direction of the sheet using measured values of this tensor, it is found that the real and imaginary parts differ largely in the principal direction for some of the rubber sheets with carbon used for this measurement.
Suppression of ground clutter using an X‐band radar
Authors: Iwama Tsukasa , Sekine Matsuo , Musha Toshimitsu 
Published: July 2007

AbstractMost of the clutter received by an L‐band air route surveillance radar obeys Weibull distribution with various values of the shape parameters. The L‐band radar has a frequency of 1.3 GHz and pulsewidth of 3 μs. Hence, the spatial resolution is as large as 450 m. The X‐band radar, on the other hand, ns. frequency of 9.4 GHz and pulsewidth of 80 ns. The spatial resolution is as small as 12 m; we have found that the clutter amplitude distribution obeys a composite Weibull distribution when reflectors are ordinary terrain and such structures as buildings. Clutter suppression techniques for Weibull and non‐Weibull echos are proposed.
The optimum interpolatory approximation of waves using time limited interpolation functions
Authors: Kida Takuro 
Published: July 2007

AbstractAn investigation has been conducted about the interpolatory approximation of waveforms using a set of sample points in the form of groups of K generally non‐equidistant sample points which are arranged periodically over a time axis. First, we consider a set Γ of waveforms f(t) whose Fourier spectra F(ω) are bandwidth limited in |ω| ≤ ω1 and which satisfy \documentclass{article}\pagestyle{empty}\begin{document}$ \int\limits_{ - w_1 }^{w_1 } {|F(w)|^2 } /W(w)dw \le A(> 0) $\end{document} for some positive weight W(ω). The interpolation function, which minimizes the supremum of the absolute error between the original waveforms f(t) and the corresponding approximation waveforms over Γ, is derived. Here the approximate waveforms are taken to be the total sum of the values at the sample points mentioned above multiplied by the interpolation functions time‐limited to a finite time‐band centering at the corresponding sample points. A choice of time limitation of the interpolation function discussed above is fundamental for realization of interpolation functions by a FIR filter. If displacement along the time axis is ignored, the optimal interpolation functions mentioned above are divided into K groups and it is shown that they satisfy the orthogonality for a finite sum. Next, using the concept of an inner product expression of a quasi‐bilinear form, an extension of the above concept is made and the optimal interpolation function is derived. The extension includes a case in which sample values contain statistical errors and a case in which the original wave is reproduced using sample values of linearly transformed waveforms.
Quantization error in differential PCM of laplacian increment inputs
Authors: Hayashi Akira 
Published: July 2007

AbstractQuantization error is one of the important measures that determine the performance of the differential PCM. This paper investigates the DPCM quantization error characteristic and the exact determination of the stationary error density. The input signal considered is a time‐discrete increment process which is similar to the Wiener sequence, but with Laplacian increments.A system of equations satisfied by the characteristic function of the prediction error is derived first and the exact formulas are derived for error probability distributions. Using these distributions the meansquared error, the entropy of the quantized outputs, and the probability of granular error are determined. For the obtained optimum quantization step size, it is shown that the granular error exceeds the slope overload error, that the distribution of quantized outputs is nearly geometrical, that the quantization error is almost equal to that of increments for a large number of quantization levels, and that the results agree with rate distortion theory.The present analysis will be useful to performance analysis of DPCM with stationary non‐Gaussian autoregressive inputs.