bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some design methods for two‐dimensional digital filters with complex coefficients in consideration of linear phase characteristics
Authors: Ichikawa Yaoji , Takahashi Shin‐Ichi , Members Regular 
Published: July 2007

AbstractIn designing a two‐dimensional digital filter with special consideration of the phase characteristics, particularly the group delay characteristics, a very high‐order filter is generally required. This paper extends the coefficients of the filter from real to complex and describes a design technique for comparatively low‐order, two‐dimensional, circularly symmetric filters with consideration of phase characteristics. First, the method of transforming a two‐dimensional input signal into an analytic signal is described and then the design technique of two kinds of complex coefficient filters which use the properties of analytic signals is discussed. In the first kind variable transformation to a 1‐D real coefficient FIR filter is used to obtain a 2‐D FIR filter with complex coefficients. It has the merits of permitting independent setting of the sharpness of cutoff characteristics and circular symmetry. In the other kind of complex coefficient filter a recursive digital filter is obtained by using an all‐pole filter having constant group delay in the passband of the transfer function and having a 2‐D complex coefficient mirror image polynomial. It always has a constant group delay unrelated to the values of the coefficients and the overall group delay is also constant. Moreover, in this paper, design examples based on these methods are given and the validity of our methods is shown.
Scattering of electromagnetic fields by two strips located near a line source
Authors: Nishimoto Masahiko , Aoki Kazuo , Yoshidomi Kuniaki 
Published: July 2007

AbstractThe electromagnetic field scattered by two conducting strips located near a line source is calculated rigorously by using a cylindrical wave expansion. Numerical results are given for radiated far‐fields. As a simple approximate calculation of the present problem, one method similar to the Geometrical Theory of Diffraction (GTD) is also proposed. In this method the scattered field by the strips is approximated by the superposition of those scattered by the conducting half‐planes. It is found from the numerical comparison of the rigorous solution with the approximate one, that both results agree well and that the present approximate method is applicable to the case where the source and the edge are too close for the GTD. The condition of applicability is studied for the present method as applied to a strip grating with finite elements.
Numerical analysis of lock range of a phase‐locked loop with an interfering signal
Authors: Takahashi Yutaka , Kawabe Manabu , Chiba Shin‐Ichi 
Published: July 2007

AbstractThis paper presents a numerical analysis method for the lock range, with respect to the desired signal, of a PLL with two input signals, one being the desired signal and the other an interfering signal. We first consider the phase comparator using a multiplier and determine the model for analysis of the PLL with two unmodulated and noiseless input signals. Next, using harmonic analysis of the nonlinear differential equation derived from this model, we present a method of computing the periodic solution generated by the interfering signal within the PLL. In this numerical computation the detuning of the desired signal is determined as the dc component of the solution, and the stability limits of the periodic solution become the lock range. Finally, we determine the lock range as a function of the amplitude ratio of the desired and interfering signals. Computed examples are presented for appropriate parameters and the results are found to match the experimental data.
90‐degree differential phase shifters using meander‐line networks
Authors: Iwakura Hiroshi , Hamaguchi Masakazu , Sato Risaburo 
Published: July 2007

AbstractA differential phase shifter uses two all‐pass networks with different electrical lengths and obtains a constant differential phase output from the difference in phase characteristics of the two networks. Since conventional phase shifters basically consist of two‐wire coupling lines and uniform lines, they are relatively large. In this paper, two types of differential phase shifters are proposed to obtain compact circuit geometry by using meander‐line networks. First, meander‐line all‐pass networks are used to construct the phase shifter. Although the differential phase output bandwidth becomes small compared with that of conventional phase shifters, the circuit geometry can be made compact. Next it is shown that the phase shifter consisting of transformers with transformation ratio 2:1 can match the input port and that it can be miniaturized while yielding a similar differential phase output. Within the design band the output ratio of the two networks becomes close to unity and hence the phase shifter can be used as a branching circuit with constant phase difference.
Software configuration of the data‐flow control exchange DATAFLEX‐1
Authors: Akiyama Minoru , Yamashita Mikio , Misu Toshiyuki 
Published: July 2007

AbstractThis paper describes the software configuration of data‐flow control exchange DATAFLEX‐1 which was proposed and fabricated to resolve the software bottleneck problem brought by “von Neumann” style single‐processor centralized control. This experimental machine uses a basic operation element whose size is about that of a task macro and incorporates data‐flow control computer architecture in its execution rule. First, call processing programs are implemented on this machine with seven Z80A microprocessors onboard to realize an intra‐office connection. Then, effective methods on fault detection/ recovery are examined and some principal parts of these processes have been implemented on it.
Automatic equalizer including a decoder of error‐correcting code and its development
Authors: Kohno Ryuji , Imai Hideki , Hatori Mitsutoshi 
Published: July 2007

AbstractThis paper proposes an automatic equalizer containing a decoder for an error‐correcting code. The purpose is the comprehensive compensation of code errors caused by intersymbol interference due to band‐limitation and code errors caused by channel variation and noise. These are major problems in realizing a highly reliable communication. The system is called AEDEC and can reduce the correction error in the tap coefficient innovation due to decision error and the error propagation in a decision‐feedback scheme. Consequently, it can achieve a stable convergence in the channel in an adverse condition where a traditional automatic equalizer cannot lead to a convergence. A control method is proposed for innovation of a tap coefficient and data feedback before the feedback decision based on the decoding reliability. This is estimated in the decoding process of the error‐correcting code leading to the optimum control, and minimizing the effects of undetection or miscorrection of the decoding errors. Furthermore, as an extension of AEDEC, an adaptive canceller is proposed which eliminates the intersymbol interference without emphasizing noise by utilizing AEDEC as a means of preliminary decision. As a result of computer simulation applying algebraic decoding and analog‐weight minimum decoding to recursive (7, 4) Hamming code, it is shown that the proposed schemes can lead to a stable convergence, thereby drastically improving the bit‐error rate.
Multiple access system using linearly independent vectors over a finite field
Authors: Ogiwara Haruo 
Published: July 2007

AbstractFor arbitrary l terminals among n terminals scattered over a space, we prepare a set of n vectors over a finite field among which arbitrary l vectors are linearly independent. Each vector is assigned to each terminal, and messages correspond to elements of a finite field in proper block units. A code‐division multiplex communication system is proposed in which arbitrary 1 terminals can transmit simultaneously to a center station through a common transmission line. Then the terminals synchronously add the products of the message and the vector to a common transmission line over a finite field. This system does not need common control nor collision detection/retransmission processing for channel assignment and has high transmission efficiency. First, this paper discusses the bound of transmission efficiency. Then it is shown that high transmission efficiency can be obtained if the block length k of the message is taken large. Then the relationship of (n, l, k) is clarified for the case where column vectors of parity check matrices of the BCH code and the Reed‐Solomon code are used as the above vectors, and for this case the above set of vectors is made up of products of distinct irreducible polynomials. A specific coding method is given for obtaining high transmission efficiency.
Magnetic circuits of lumped‐element circulator with thin‐type structure
Authors: Takeda Shigeru 
Published: July 2007

AbstractLumped‐element types are used most often for circulators and isolators for few tens MHz ∼ 1 GHz applications. In the conventional lumped‐element circulators, size and power handling capability are not very desirable due to two magnets. This paper proposes a new magnetic circuit that uses only one magnet and has a good thermal balance without degrading the electrical characteristics. In this circuit, a microwave garnet is sandwiched between two soft magnetic materials without air gaps. A permanent magnet is contacted on one side while a heat sink is attached on the other side. The structure is thin. First, the theoretical foundation of the present magnetic circuit is described. Then the theoretical and experimental results of the magnetic field distributions are compared. Various experimental results including that for the temperature characteristics as well as the practical test results, are presented for a lumped‐element circulator consisting of the present structure. It is confirmed that with a garnet of given dimensions, the lumped‐element circulator of half the height and more than three times the power handling capability can be realized.
A comparison of adaptive antennas on desired signal arrival angle errors
Authors: Ohmiya Manabu , Ogawa Yasutaka , Itoh Kiyohiko 
Published: July 2007

AbstractIn the Howells‐Applebaum adaptive antenna (H‐A) and the directionally constrained least mean‐squares adaptive antenna (CLMS) their abilities are degraded due to an angular error in the assumed direction of a desired signal. In this paper, several methods of preventing the angular error are compared. One of them is the decrease of the amplifier gain in H‐A, or in the increase of pseudo‐noise in CLMS so that the diagonal elements of the correlation matrix derived from input signal S are equivalently increased. Another is the use of multiple directional constraints in CLMS (multidirectional CLMS) where the number of constrained directions is increased. The effects of these methods are checked by numerical calculations. The evaluation criteria are set so that the angular error is 5 degrees, the upper limit of the dynamic range of the input SNR is. 20 dB, and the lower limit of the output SNR or SINR is 10 dB. Comparison is performed under the condition that the degrees of freedom for the antennas are kept constant. The multiple CLMS is the best way to satisfy the evaluation criteria in a wide range of arrival of interference if interference power is equal to or smaller than the desired signal power. On the other hand, the method for effectively increasing the diagonal elements of the correlation matrix is the best if interference power is larger than the desired signal power. However, when the countermeasure for the angular error suitable for signal environments is chosen from the above two, the choice depends on the evaluation criteria.
Progressive facsimile coding scheme for interactive image communications
Authors: Endoh Toshiaki , Yamazaki Yasuhiro 
Published: July 2007

AbstractRecent developments have led to increased application of interactive image communications in teleconferencing and video disc systems. Many of these systems have facsimile transceivers as subsets. However, since conventional facsimile devices provide only hard copy, some soft copy display devices are desirable for interactive image communications. This paper proposes a progressive facsimile coding scheme for interactive image communications. This scheme permits rapid browsing of the images and image quality can be improved progressively if required. Simulation and experimental results indicate that the proposed scheme is more efficient than the standard coding scheme for G4 facsimile. Using the progressive coding scheme, the contents of most images can be recognized after 30 to 40% of the total transmission time. The applications of this efficient coding scheme in interactive image communications and the storage and retrieval of images are discussed.
Determination of installation cable size and the ratio of common fibers to total fibers in subscriber optical fiber cable network
Authors: Yamamoto Hideo , Yamamoto Yoshikazu , Matsuura Masaaki 
Published: July 2007

AbstractTo construct an efficient subscriber optical fiber cable network, a highly economical and versatile distribution method is needed. This paper clarifies a technique in which by determining the installation cable size of feeder system and the ratio of common fibers to total fibers, a balance between the service requirement and cost is obtained.First, gamma distribution, practically used for metal cables, is applied to the demand forecast error distribution and the relation between the number of fibers and the ratio of common fibers to total fibers, which is required to obtain the desired equipment reliability, is clarified. Next, the relation between the cross‐connecting probability is determined and utilizing the ratio of common fibers, the cost function of optical cable system is derived. Here, both the cable installation cost and cross‐connection cost are considered. These two factors are combined and a design method of installation cable size and the ratio of common fibers to total fibers is clarified. This method ensures the desired equipment reliability and is the most economical one. Using this method and assuming all the various costs, it is clarified that for high cross‐connection cost, a cable having a large number of fibers should be installed and the cable network construction having comparatively low ratio of common fibers to total fibers is desirable. When the cross‐connection cost is less, the installation cable having a smaller number of fibers and a higher ratio of common fibers to total fibers is desirable. Moreover, with these results in mind, an economical subscriber optical fiber cable network construction is proposed.
Relations between the possibility of restoration of bandpass‐type band‐limited waves by interpolation and arrangement of sampling points
Authors: Kida Takuro , Kuroda Tohru 
Published: July 2007

AbstractA study has been conducted on band‐limited waves f(t) of bandpass type, the Fourier spectrum F(ω) of which is identically zero outside an occupied band ωτ < ∥ω∥ < ωτ + ωb. Based on this study, we have obtained the following results: first, when an interpolation of a wave is attempted using a set of even‐numbered samples periodically repeated on both sides of the time axis at a mean distance between samples π/ωb (which in general are arranged ununiformly), the necessary and sufficient condition for said samples to restore a desired band‐limited wave having the same occupied bandwidth is demonstrated; second, a concrete formula of interpolation using a set of the prescribed type that satisfies the necessary and sufficient condition above, is introduced. Then a proof that demonstrates the impossibility that a formula which permits a set of samples of an odd number is periodically repeated at a mean interval of π/ωb to restore any desired band‐limited wave having the prescribed occupied bandwidth on the basis of interpolation unless ωτ or ωb satisfies a special condition. Finally, relations between the possibility of interpolation and combinations of ωτ and ωb for sample positions restricted to a certain extent if the mean interval between sampling points is shorter than π/ωb, is discussed.
Simulation of impedance‐scaled LCR filters with voltage followers
Authors: Takagi Shigetaka , Fujii Nobuo 
Published: July 2007

AbstractLC simulation by active RC circuits generally requires an equal or a higher number of active elements than the order of the filter. This is one of the main difficulties that delays their practical applications as compared to cascade realizations. This paper proposes a method to simulate impedance‐scaled LCR filters using an equal or a lower number of voltage followers than the number of nodes in the original LCR filter. The influence of the imperfections of the voltage followers is also investigated. As simple examples, a 4th‐order bandpass filter and a 4th‐order lowpass filter are realized. Measurements and sensitivity analysis are performed on the 4th‐order bandpass filter and the results demonstrate the high performances of the method as compared to the other methods.
Interactive decision‐making for multiobjective nonlinear programming problems using fuzzy satisficing regions
Authors: Sakawa Masatoshi , Nango Yuji 
Published: July 2007

AbstractIn this paper, it is assumed that the ambiguous requirement and desired level of the decisionmaker for the objective functions in the multiobjective nonlinear programming problem can be quantified by eliciting the corresponding membership functions interactively. Then the region for the desired solution, called fuzzy satisficing region, is specified for the membership function by a membership value (required membership value) which is the minimum‐required value to be achieved, and another membership value (desired membership value), which should desirably be achieved. For such a fuzzy satisficing region of the decisionmaker, the penalty and the barrier functions are used to maximize the overachievement for the required membership value, and to minimize the underachievement for the desired membership value. In this way, the Pareto‐optimal solution for the specified fuzzy satisficing region is presented to the decisionmaker. The decisionmaker is either satisfied with the achieved Pareto‐optimal solution, or updates, on subjective basis, the required and the desired membership values. By reducing the fuzzy satisficing region in this way, it is possible eventually to derive the solution satisfactory to the decisionmaker from the set of Pareto‐optimal solutions for the given problem, through relatively simple interactive processes. An interactive computer program is constructed based on the proposed method, and an example for the course of interaction is shown for a numerical example.
A method of time‐domain approximation using the transfer function whose attenuation poles are restricted on the imaginary axis
Authors: Kida Takuro , Fukuda Yutaka 
Published: July 2007

AbstractIn the transfer function with zeros restricted on the imaginary axis of S‐plane the phase characteristic is essentially determined by that of the denominator polynomial. As long as the denominator polynomial is a Hurwitz polynomial, the tangent of its phase characteristic, i.e., the ratio of the imaginary part (odd part) to the real part (even part), is a reactance function. This paper proposes a waveform approximation method which approximates the phase tangent of the Fourier transform of the object waveform by a reactance function using an optimization technique. The Hurwitz polynomial, which is the sum of the numerator and denominator of the reactance function, is adopted as the denominator polynomial of the approximate transfer function. The numerator polynomial of the approximate transfer function is derived by adjusting the zeros on the imaginary axis by an optimization technique to approximate the amplitude of the Fourier transform of the object waveform. An evaluation measure in the proposed approximation method is presented, describing its problems and physical implications. It is shown that the proposed method can provide a satisfactory approximation for symmetrical waveforms. For asymmetrical waveforms it is shown that the approximation can be improved by adding a delay time. An appropriate weighting function is proposed for the evaluation measure. Lastly, the proposed method is compared with other methods of approximation.
A practical design of circularly polarized printed array antenna composed of strip dipoles and slots
Authors: Ito Koichi , Kitajima Hiroshi 
Published: July 2007

AbstractIn earlier papers, we proposed a circularly polarized printed array antenna composed of strips and slots (CP‐PASS). We showed that it possessed good properties such as a good axial ratio, a relatively high gain, and had sufficient frequency bandwidths. The purpose of this paper is to obtain a practical design method for CP‐PASS in order to realize a desired radiation pattern or to increase further its antenna gain. First, an equivalent circuit model of a basic element set of CP‐PASS is represented taking into account interelement couplings and a feed line loss. On the basis of the equivalent circuit model, design conditions of circular polarization and input impedance matching are formulated for a normal use of CP‐PASS. Second, satisfying the above conditions, a procedure for determination of an arrangement, dimensions and input impedance of the elements is described to realize desired antenna properties. Numerical examples of CP‐PASS with uniform aperture distributions are shown to clarify its fundamental characteristics. Third, a practical method for determination of the element lengths and coupling gaps is described on the basis of the basic radiating‐element characteristics obtained before. Finally, to demonstrate the validity of the design method presented here, a Chebyshevarray CP‐PASS consisting of four element sets is designed and tested as an example.
Picture coding by an adaptive multistage vector quantization
Authors: Uda Toyokazu , Saito Tsuneo 
Published: July 2007

AbstractAn adaptive multistage vector quantizing system is proposed for highly efficient picture coding method and its coding performances are investigated. This system contains a multistage vector quantizer which means that comparatively large picture blocks are quantized first, then the remaining quantization error is quantized in smaller blocks, gradually refining the resolution at subsequent stages. That is, a rough picture is coded first and finer structures are coded later. Computer simulation studies on several picture samples demonstrate the excellent processing efficiency of the proposed method in comparison with conventional vector quantizers.