bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of write head saturation on the characteristics of digital magnetic recording
Authors: Nishikawa Masaaki , Kirihara Akio
Published: July 2007

Although there have been various theories on the effect of the magnetic saturation of a write head on the recording characteristics of a magnetic medium, they include many vague points. to obtain a complete picture of the effects, this paper compares the digital recording characteristics. These have been obtained by changing the starting point of the saturation of a write head over a wide range referring to the saturation point of a magnetic medium (the variation is made utilizing the temperature characteristics of ferrite used for the head). When the head is not saturated, in both the unsaturated region and the highly saturated region of the medium, the recording characteristics of the medium depend greatly on the recording magnetic field strength. This dependency is less in the region between the two regions. In the two regions, if the head is saturated, the variation of the write characteristics due to the write current is restrained after saturation. In the intermediate region, if the pole tip is saturated, the write characteristic is somewhat degraded. If the head is saturated around the intermediate region, the overwrite erase rate is greatly degraded, since this is sensitive to the erase magnetic field strength around the saturation point of the medium.
An algorithm for generation of s‐t acyclic graphs
Authors: Higashiyama Youichi , Ariyoshi Hiromu
Published: July 2007

The problem of finding all s‐t acyclic graphs between two given vertices of a digraph is interesting in relation to the evaluation of the reliability of a communication network. There is already an algorithm which generates all s‐t acyclic digraphs without duplication by opening an arc or a set of arcs one by one starting with a given graph. But the efficiency of that algorithm decreases when the number of cycles in the graph becomes large. This paper proposes an algorithm which generates s‐t acyclic graphs without duplication by combining s‐t paths obtained by a depth‐first search. Compared with the existing algorithms (i) the execution time of this algorithm is not affected much by the number of arc disjoint cycles of the graph; (ii) when the generation is stopped at an arbitrary level i, all the s‐t acyclic graphs composed of paths of length i or less will have been generated. Thus they can be used to approximate the reliability.
Design and characteristics of standard launching fiber for optical loss measurement
Authors: Tokuda Masamitsu , Horiguchi Tsuneo , Ueki Akihide , Oshima Toshio , Tanaka Masao
Published: July 2007

We have studied a standard launching filter, which can realize a field distribution close to the steady‐state modal field in the optical‐loss measurement of graded fibers and can be used as a reference fiber in the splicing‐loss measurement by a back‐scatter method. By using a small‐core fiber with the core radius 30 ‐ 40 μm, which is smaller than that of the fiber to be measured (50 μm), we realized a field distribution close to the steady‐state modal field. It was found that the variation of the excited modal distribution due to a difference in the radiation pattern of the optical source can be reduced by inserting a graded fiber and a step‐index fiber between the source and the small‐core fiber. When a fiber with a standard backscattering coefficient is placed between a small‐core fiber and the fiber to be tested, it becomes possible to apply the splicing‐loss measurement based on the backscattering technique. The optical loss measured by a standard fiber designed for the 1.3‐μm wavelength agreed with the value at the steady‐state modal distribution within ±0.05 dB/km. It was found that the optical loss at 0.85 μm can be measured within ±0.1 dB/km by using the same standard fiber. From these studies, it now becomes possible to measure the optical loss and the splicing loss with high precision.
Arc‐fusion splice of multimode optical fibers using pre‐fusion method
Authors: Miyauchi Mitsuru , Matsumoto Michito
Published: July 2007

In optical fiber splicing, the fusion technique using gas discharge heating is considered a practical method from the viewpoints of operation and reliability. The fusion by which the splicing is made after pre‐shaping by a gas discharge on the optical fiber ends, has excellent features of low loss and stable splices. However, the splicing mechanism and the optimum splicing condition have not yet been analyzed sufficiently. This paper studies splicing conditions such as the pre‐fusion time, optical fiber stuffing length and shape‐up time of the optical fiber splicing by pre‐fusion method from the viewpoint of splicing shape, splice loss and core distortion. The optimum conditions for realizing a low‐loss splice are then determined. As a result, it is clarified that although the pre‐fusion method essentially becomes a mechanism for increasing the splice loss due to core distortion caused by pre‐fusion, there exists an optimum stuffing length for minimizing its effect. It is also shown that for performing stable, low‐loss splicing (even in the case where the condition of the optical fiber end is bad), it is proper to have a pre‐fusion of 0.3 ∼ 0.4 second. A foundation for the design of the splicing apparatus is obtained.
Improvement of signal‐to‐noise ratio in a combination of a linear and a nonlinear amplifier
Authors: Shinriki Masanori , Member Regular
Published: July 2007

In general, when a signal with noise is applied to a nonlinear amplifier, the nonlinearity will suppress either the signal or the noise. This property is utilized in this paper; the input signal is applied to nonlinear and linear amplifiers and an output circuit forms their difference. It is found that such a circuit can markedly improve the signal‐to‐noise (S/N) ratio of an input signal containing strong noise. Simple saturation nonlinearity is produced by an element xν(ν < 1); with ν>1 extension‐type nonlinearity characteristics result. A general type of noise is treated as a narrowband noise with a Weibull amplitude distribution. Analysis shows that when the Weibull coefficient is small, the use of the saturation characteristics of a nonlinear amplifier improves the S/N ratio considerably; when the Weibull coefficient is very large, neither extension‐ or saturation‐nonlinearity shows a marked difference. If the signal is contained in narrow‐band noise of constant amplitude, tests confirm the effectiveness of the theory.
Temperature characteristics of optical fiber cable installed on aerial line
Authors: Matsumoto Michito , Saito Takeo , Hirose Mitsuhide
Published: July 2007

When an optical cable is installed on an aerial line, it will be affected strongly by the temperature and vibration due to wind. Therefore, it is necessary to grasp these effects quantitatively and establish a design method for the optical cable which will not be controlled by weather conditions. For this reason, we hypothesize a line close to the actual form and construct a 48‐core optical cable using a lashing machine, and then investigate the effects of temperature between ‐20°C and 60°C on the optical cable. The mechanical behaviors of the cable include the following: (1) Relative displacement between the strand and the optical cable accompanies temperature variations. The displacement is approximately 30 mm maximum at the end of a cable 57 m long; (2) Relative displacement between cable sheath and core occurs due to the release of the residual strain during manufacturing. It is 18 mm in the case of a 57 m cable; and (3) About 200 kg thermal stress occurs at the cable end, however, only about 10 kg in the vicinity of the slack. Based on the above experiment, the mechanical behavior of the optical cable is analyzed theoretically by setting up a simple model. It is confirmed that the analytical results agree very well with the experiment results. Variation of optical loss increases at approximately 0.15 dB/km at 60°C and this is about the same change as drum‐wound cable.
Performance of a microwave amplitude limiter using GaAs MESFET
Authors: Komaki Shozo , Kurita Osamu
Published: July 2007

This paper explains the input/output power and AM‐PM conversion characteristics of an amplitude limiter using GaAs MESFET. It is also pointed out that the AM‐PM conversion can be minimized conveniently by adding inductance in parallel to the gate terminal. In this paper the FET equivalent circuit is used for a calculation from which the relationship between the AM‐PM conversion and the gate series resistance, driving source impedance and the added inductance is clarified; the design method for minimizing AM‐PM conversion is established. The measured charactersitics are found to be the same as predicted by theory, and the correctness of the analysis is confirmed.
Non‐stop controlled vertical scanning technique for high‐speed digital facsimile
Authors: Suzuki Ryota
Published: July 2007

For high‐speed facsimile with redundant supression code, the intermittent variable scanning system has traditionally been used, accompanied by the start/stop function for the vertical scanning. However, the system requires a certain settling time in stopping and a limitation is imposed on the speed when the vertical scanning mechanism is heavily loaded. From such a viewpoint, this paper proposes a nonstop vertical scanning system, which realizes a smooth vertical scanning operation without stopping the vertical scanning. In the proposed system, the vertical scanning speed is predetermined in N steps and, by comparing the stored bits in buffer memory and threshold values for the buffer memory, the vertical scanning speed is determined as the same as the previous one or one step faster or slower. By this elaboration, a high‐speed system can be realized even when the load is heavy, at the same time achieving low‐noise operation. In the present system, however, selection of the vertical scanning speed is limited to one of three, which prevents the system from complete follow‐up change in the code information, necessitating a line memory and buffer memory. This paper first describes the design method and control scheme for the vertical scanning speed and then presents the result of calculation and computer simulation for the relation between various parameters and the memory capacity. The effectiveness of the proposed system is verified by an implementation. The memory capacity is evaluated at the same time, comparing the capacities of the two kinds of memories.
An intensity/phase autocorrelator for measurement of an ultrashort optical pulse having frequency variation
Authors: Kurobori Toshio , Cho Yoshio , Kanda Masahiko , Matsuo Yukito
Published: July 2007

An autocorrelator which can provide the intensity and phase correlations of an ultra‐short optical pulse simultaneously is presented. This is accomplished by employing an alternate repetition of fast and slow scans to separate the intensity and phase correlations. The proposed autocorrelator is also equipped with the junction of a real‐time monitor for the rapidity and ease of complex adjustments to optimize the various parameters in a mode‐locked laser. Such autocorrelator is useful for measuring ultrashort optical pulses containing frequency variations.
Image reconstruction of long‐wavelength holograms by maximum entropy method
Authors: Yamamoto Tsuyoshi , Aoki Yoshinao
Published: July 2007

Application of the maximum entropy method to one‐dimensional holographic imaging system is proposed. Image reconstruction usually is performed by the Fourier transform method. In this paper, however, the maximum entropy spectral estimation is used instead of such a transform. In digital processing the DFT algorithm is used instead of the Fourier transform, but it requires the quantization of coordinate system of both object and hologram plane. Such quantization sometimes makes the reconstructed image degrade if the position of the objects is not on the quantized position. To avoid such degradations, using windows or increasing the number of data must be considered. However, information in the hologram data will be lost by using such a window. In contrast to a Fourier transform method, this technique can evaluate the image continuously on the object plane; thus degradation caused by quantization of coordinate does not occur. While image reconstruction by the Fourier transform method is a linear operation, this technique is non‐linear. Therefore, linear superposition property of reconstructed image is not guaranteed. Further, the image is obtained by evaluating an all‐pole filter; thus this technique gives good reconstruction if the objects are pointed. Experimental results using ultrasound are presented. These show that this method gives good images even when little data are used.
Miniaturization of stripline hybrid coupled diode phase and shifter and its wavebanding method
Authors: Matsunaga Makoto , Takeda Fumio
Published: July 2007

This paper describes miniaturization of a hybrid coupled diode phase shifter made of striplines and its widebanding. An impedance transformer setting the phase shift of a single‐bit phase shifter is fabricated with a coupled line with two open ends having a bias blocking capability. This makes the size of the phase shifter about one‐half of the conventional one. It is pointed out that a wideband characteristic of this phase shifter is possible by choosing a large ratio of the even‐mode impedance to the odd‐mode impedance in the coupled line. An S‐band hybrid coupled phase shifter fabricated based on the present design method has a phase error less than 7.4 (RMS value) in the relative bandwidth of 26%, a loss of less than 1.4 dB and a VSWR of less than 1.6.
Probabilistic analysis of a sequential algorithm for finding independent sets
Authors: Kawaguchi Tsuyoshi , Nakano Hideo , Nakanishi Yoshiro
Published: July 2007

This paper uses the constant group average degree model, which is a generalization of the constant average degree model, and evaluates the method of solution given in [1] to determine the independent vertex set. The model is a set of graphs in which there exist edges with probability pij = cicj/cn (c Σmi=1 ci|Vi|/n) independently between two vertices v and w such that v ϵ Vi and w ϵ Vj in the vertex set V = Umi=1Vi. When m = 1 holds as a special case, the model includes the constant average degree model. It is shown first that the stochastic variable BG(n, c) representing the solution by the method of [1] satisfies (1 ‐ ϵ) βG(c)n < BG (n, c) < (1 + ϵ) BG(c)n (pr.), where ϵ = 0 is sufficiently small compared with 1 and BG(c) is a value obtained by solving a recurrence formula. Then it is shown that the stochastic variable BG*(n, c) representing the size of the maximal independent set satisfies BG*(n, c) ≦ (1 + ϵ) αG(c)n (pr.), where αG(c) is a value obtained by solving an equation. The results obtained in this paper are applicable to the constant group average degree model with any |Vi| and ci.
Variable‐hue light‐emitting diode using a single crystal chip
Authors: Shimura Hideo
Published: July 2007

Monochromatic light‐emitting diodes of different sizes and colors are widely used as small display devices. However, diodes of different colors for commercial purposes are those having a combination of red light‐emitting pellets and green light‐emitting pellets. Such a combination involves problems of color uniformity and brightness degradation. Therefore, a single pellet which has different uniform colors was proposed several years ago, but it has not yet been marketed due to many technical difficulties. The authors succeeded in making a single pellet with a green light‐emitting part and a red light‐emitting part on both sides of a GaP substrate. By changing the current ratio of the current flowing through the device, different colors were attained. This paper deals with different technical problems associated with device fabrication and the solutions to these problems. Also, electrical and optical properties of the device are discussed.
Evaluation of the exponent function E(R) for channels with intersymbol interference
Authors: Sasano Hiroshi , Kasahara Masao , Namekawa Toshihiko
Published: July 2007

The exponent function E(R), a practical measure, is used to study two kinds of decoders having 2l (l = 1, 2, …) quantization levels in a communication channel with inter‐symbol interference: a decoder which takes account of channel memory, and a decoder which does not. The values of E(R) for the same kind of decoder and an increased number of quantization levels, and for the two different kinds of decoder and the same number of quantization levels, are analytically compared for a channel with intersymbol interference of length 1. It is shown that increasing the number of quantization levels for a given type of detector, or taking account of channel memory with a given number of decoder quantization levels, can decrease the upper limit of the error probability. A comparison of channel capacities is shown to yield similar conclusions. Numerical computations indicate that when a decoder which takes account of intersymbol interference is used, the rate of improvement in the upper limit of the error probability is greater for a higher degree of intersymbol interference, but that further increases in the number of quantization levels produce almost no further improvement in such a situation.
Measurements of millimeter wave reflection coefficients over wide frequency range by using a special T‐junction
Authors: Iwasaki Takashi , Nagatsuka Akio
Published: July 2007

Many millimeter‐wave applications make use of their wideband nature. Hence, it is desirable to have a broadband method for measuring fundamental quantities of millimeter‐wave circuits at many frequency points in a short period of time. This paper reports a method for wideband measurement without adjustment. It is an extension of the T‐junction method in which reflection coefficients can be measured with a simple circuit. In the T‐junction method, it is necessary to reposition the movable short at each frequency for measuring a characteristic quantity of the system. This makes wideband measurement difficult. We developed a method that enables wideband measurement by using a special T‐junction in which the width of the E‐plane of the waveguide connecting the load is narrowed. In accordance with the theoretical study, a T‐junction was designed and fabricated. The experiment at 29 ‐ 39 GHz indicated that wideband measurement is possible. The estimated error of the absolute value of the reflection coefficient of the load at 34.0 GHz is less than 0.0064 |Γ| + 0.002 for |Γ| less than 0.3.
Switched‐capacitor amplifier and applications
Authors: Seki Hideaki , Yamamoto Masahiro , Mori Shinsaku
Published: July 2007

Switched‐capacitor amplifiers are proposed which consist of a switched‐capacitor circuit in the bias circuit and the load circuit of the amplifier. In this switched‐capacitor circuit, the characteristics can be changed simply by change of control clock. The circuit is suitable for integration. Recognizing that the active device in the switched‐capacitor amplifier operates intermittently, we can feed back the amplified signal to the input and amplify further. This signal recursive switched‐capacitor amplifier is discussed. Even though this switched‐capacitor amplifier is equivalent to a conventional multistage cascaded amplifier, it can be configured with only one active device and one set of peripheral components. Hence, it has a small size and a high gain. Finally, it is demonstrated by means of an example of configuration of a bandpass filter that the conventional switched‐capacitor network can be miniaturized further with the use of the proposed switched‐capacitor amplifier.
Dielectric waveguide‐type millimeter‐wave modulator using photoconductivity
Authors: Member Kazuhiko Ogusu, Regular , Member Ikuo Tanaka, Regular
Published: July 2007

Optical control of millimeter‐wave propagation in dielectric waveguide can be achieved by using the photoconductivity of a semiconductor. A semiconductor with short lifetime and an intense light source are required for high‐speed modulation. The present paper proposes a new waveguide structure providing the greatest possible attenuation with a given light intensity. The theoretical and experimental considerations are presented. The proposed structure is a rectangular waveguide in which a thin semiconductor layer is supported by a dielectric layer with small dielectric constant. Numerical results are presented on the variation of the attenuation constant of millimeter waves for various waveguide dimensions and dielectric constants. It is also shown that this waveguide structure can be utilized as a mode filter. The modulator and mode filter are made of Si, SiO2 and Teflon and tested at 50 GHz. It is found that modulation up to ∼100 kHz can be achieved even by using conventional light‐emitting diodes.
A discrete optimization method of switched capacitor filters
Authors: Fushimi Shigeo , Nakayama Kenji
Published: July 2007

When constructed on a monolithic IC, switched capacitor filters (SCF's) composed of capacitors whose values are integer multiples of a unit value are desirable for miniaturization and reduction of power consumption, since high‐precision capacitance ratios are realized using a small unit capacitance value. This paper describes a discrete optimization method of SCF. Variables which are effective to optimization are selected based on “normalized sensitivities,” which are sensitivities at a certain sampled frequency point divided by the absolute sum of sensitivities at all sampled frequency points. The min‐max method which minimizes the maximum deviation is used to evaluate the optimization error. Initial discrete values of capacitances are determined by multiplying the pre‐quantization capacitance by a positive constant and then minimizing the mean square error of their ratios. Finally, this optimization is applied to an 8th‐order biquad bandpass filter and a 5th‐order leapfrog lowpass filter and its effectiveness is confirmed.
Stability analysis of electrical networks containing lossless transmission lines – algebraic system theoretical consideration
Authors: Ohguro Katsuhiko , Maeda Hajime
Published: July 2007

This paper deals with electrical networks containing lossless transmission lines and discusses the stability from the viewpoint of an algebraic system theory. Specifically, we discuss the effect of the initial conditions of the transmission lines on the stability of the system. We point out that the coprimeness of certain matrices determined by the transmission lines is crucially important for stability and derive an equivalent condition to coprimeness in terms of the pole‐zero cancellations, as well as the structure of the interconnections among transmission lines. An easily tractable stability criterion is developed.
Brightness induced by opposite polarities o'brien pattern
Authors: Sakata Haruo
Published: July 2007

As one of the psychological phenomena, where the brightness of the background changes by the existence of a figure, this paper describes a psychophysical measurement of O'Brien pattern with positive and negative polarities. The following results were obtained. (1) The O'Brien pattern with negative polarity has a stronger induction effect. (2) When the modulation index of the O'Brien pattern is increased, the background becomes dark by the existence of a pattern, except for the edge of the positive polarity pattern. The appearance of a Cornsweet pattern, which is composed of positive and negative O'Brien patterns, was also examined. It is concluded from the observations that the positive polarity figure has a stronger lateral inhibition, but the negative polarity figure with larger modulation index has little lateral inhibition.
Appearance of spatio‐temporal transient phenomenon on retinal locality–parallel pathways at peripheral vision
Authors: Member Haruo Sakata, Regular
Published: July 2007

The spatio‐temporal transient responses at the fovea and the periphery of the retina were measured, arriving at the following conclusions: (1) In the peripheral vision (at 9 deg. from the fovea), a bright line is produced at 1 deg. from the boundary after 100 ms from the presentation of the spatial step pattern. This indicates the existence of two pathways with temporarily different transient responses; (2) Setting a fixation point and presenting a temporally sweeping spatial step pattern, the rise‐width of the brightness step approaches the response of the temporal‐dominant pathway as the observation point goes away from the fovea. At the same time, a differentiated pattern is produced in the brightness boundary of the spatial step pattern, indicating the response of the spatio‐dominant pathway.
An estimation method for rain attenuation distribution in microwave multirelay links–compound lognormal distribution model
Authors: Member Kazuo Morita, Regular
Published: July 2007

Estimation of the rain attenuation distributions in microwave multirelay links at frequencies over 10 GHz involves estimation of the rain intensity distribution at various locations, the rain attenuation distribution in each relay path and the simultaneous probability in multirelay paths. In this paper, the yearly rain intensity distribution data at various locations are studied. It is found that the distribution can be approximated by a compound lognormal model. From the yearly rain data of the weather bureau, the rain intensity distribution parameters of compound lognormal distribution are estimated at 80 locations. It is assumed that the rain intensity is of compound lognormal distribution and the spatial correlation of rain intensity is e‐αd (α: parameter, d: distance between two points). The simultaneous probability of rain attenuation in multirelay paths is calculated. Also calculated is the correction factor Mp (the probability that at least one out of n paths/n times the probability that the attenuation exceeds the specified value at one path) of the added rain attenuation in a multirelay link with respect to the sum of probabilities of attenuation in each path. The measured Mp in the 20‐GHz multi‐relay link between Musashino and Yokosuka agrees well with the estimate Mp from the compound lognormal distribution model.
Design of two‐dimensional fir digital filters on asymmetric half‐plane
Authors: Hinamoto Takao , Muneyasu Mitsuji , Maekawa Sadao
Published: July 2007

A technique for designing asymmetric half‐plane two‐dimensional FIR digital filters in the frequency domain is presented. This filter includes the class of causal two‐dimensional digital filters as a special case. To design a linear‐phase FIR digital filter, a mirror‐image polynomial is presented for the asymmetric half‐plane two‐dimensional digital filters. The technique has an advantage of ensuring the linear phase of the resulting filters. Moreover, it is possible to design the filter by solving a set of linear equations. Two examples, low‐pass filter and fan filter designs, are solved to illustrate the proposed technique.
A design method for cascade form digital nyquist filters with zero intersymbol interference
Authors: Nakayama Kenji
Published: July 2007

In data communication systems, a Nyquist waveform shaping filter is an important element. The Nyquist filter not only restricts the bandwidth of the data signal, but also realizes zero intersymbol interference where the time response intersects zero at equal intervals except at one point. This paper discusses a design method of a digital Nyquist waveform shaping filter for sampled signals. In particular, the method proposes realization of overall zero intersymbol interference when an identical transfer function is used for both the transmitter and receiver filters. In this method, the transfer function coefficients are used as approximate variables. They are divided into coefficient xf for time response approximation and xf that approximates the frequency response. The condition for zero intersymbol interference is given as the linear equation for xt. Therefore, the approximation variable xt for realization of zero intersymbol interference is obtained from solution of the linear equation. On the other hand, the frequency response is optimized with the iterative approximation due to the observation that the relation between xf and the approximation function is nonlinear. The proposed method is applicable to both the FIR filter and the IIR filter for which the conventional method is not applicable. Further, the effect of the quantization errors in the multiplier coefficients and in the internal signal on the intersymbol interference is analyzed, and an estimation formula is obtained.
Appearance of the “movement” of a spatio‐temporal sine‐wave pattern with the retinal locality
Authors: Sakata Haruo
Published: July 2007

The appearance of the “movement” with the retinal locality is measured via a brightness spatio‐temporal sine‐wave pattern. Thus, it is clarified that the velocity threshold is superior at the fovea, the sensitivity is degraded at low spatial frequencies, and the velocity upper limit does not depend on the retinal locality. It is understood from the experimental results that the subjective appearance of movement is detected in terms of vs = DLx/Δt and is determined by the subjective temporal frequency characteristic and spatial frequency characteristic at each retinal locality.
A method for estimating the protection ratio in fm television transmission
Authors: Kubota Keiichi , Ishida Junichi
Published: July 2007

A calculation method for estimating the protection ratio in FM‐TV transmission is described. The interference between two FM carriers modulated by the NTSC or TCI color bar signal is analyzed and the baseband interference is expressed in a simple form as beat interference. Applying several weighting functions of the visual system to the beat interference, a subjective interference index which expresses the degree of subjective impairment is defined and then a method for estimating the protection ratio using this index is proposed. The protection ratios calculated by this method for various signaling systems and modulation parameters agree well with the results of subjective assessment tests. The method permits determination of the protection ratio in any FM‐TV system without subjective assessment tests for various parameters. It can be used to estimate the protection ratio in introducing new services to existing satellite broadcasting channels and to develop new channel plans.
An automatic transversal‐type ghost canceller
Authors: Obara Masaharu
Published: July 2007

A system study has been conducted on an adaptive transversal filter Ghost Canceller to achieve system optimization, and prototype ghost cancellers have been conducted on a trial basis. The results of tests showed that: (1) a Ghost Canceller for picture signals using an LSI CCD transversal filter could improve the quality of TV pictures by more than one grade in a five‐grade subjective evaluation against multiple ghost images of up to a 12‐μs delay time; and (2) a non‐CCD and totally digitalized Ghost Canceller for Teletext signals has shown a significant improvement in reducing strong short‐delay time ghost echoes and equalizing waveform distortion. This paper clarifies the system structure and the design method for both of the cancellers and shows the practical usefulness of the Ghost Cancellers.
Digital signal processing syllabic compander
Authors: Tajima Jun , Kobayashi Katsumi
Published: July 2007

At present, analog circuits are used widely for syllabic companding which effectively improves the quality of speech communication. The digitalization of the syllabic companding circuit promises several advantages, namely, the possibility of adapting filter coefficients to the condition of the radio communication system, the elimination of adjustments, the possibility of large‐scale integration, etc. The present paper considers such a new approach, a digital signal processing syllabic compander. The realization method is described and the results of both theoretical and computer aided investigations concerning the characteristics of the compander are presented. First, the construction of the digital signal processing compander is shown. Then detailed theoretical investigations are given on the influence of the distortion which is a specific problem of the digital realization. The results obtained agree well with those of the computer‐aided analysis. According to the investigations presented it has become clear that the sampling frequency should exceed 24 kHz in order to attain a signal‐to‐distortion ratio of above 40 dB in the voice frequency band for a separate compressor and an expander. However, if the compressor and expander are connected in a system, then a distortion cancellation effect arises which allows a considerable reduction of the sampling frequency. The transient response has also been investigated, and the same characteristics have been obtained as in the case of analog companders.
A unified analysis of multipath degradation in multilevel modulation radio systems
Authors: Murase Takehiro
Published: July 2007

In microwave digital radio transmission, waveform distortion due to frequency selective fading becomes a dominant factor of degradation. To evaluate the degradation of different systems in a unified way, the waveform factor is defined first. With the aid of concept “waveform factor,” the eye aperture is easily obtained. We also evaluate the waveform factors for various modulation schemes. Next, on the basis of the relation between propagation parameters and waveform factor in two‐ray fading, the estimation formula of the outage probability for various digital radio systems in line‐of‐sight propagation is derived. The proposed factor is determined uniquely by system parameters, such as modulation scheme, system impulse response, and symbol rate. With the aid of this factor, digital radio system performance during multipath fading is easily evaluated.
Visual response features by opposite polarization of brightness figure
Authors: Sakata Haruo
Published: July 2007

A difference in the brightness of the background by figures with opposite polarities is obtained by means of a psychophysical measuring method. In this method, the appearance of the background by figures with opposite polarities is a psychological phenomenon related to the receptive field of ON‐center type and OFF‐center type in electro‐physiology. The following results are obtained by psychophysically measuring the brightness within the circle of the ring target and the brightness of the intermediate portion between parallel two‐bar with positive and negative polarity.

(1) With positive polarity, lateral inhibition occurs regardless of the contrast. With negative polarity, lateral emphasis occurs when the contrast increases.

(2) The effect described in item (1) is more remarkable with the ring target than with the parallel lines.

(3) When the target size is greater, the phenomenon is closer to the brightness contrast phenomenon.
Communication media control schemes in an integrated service circuit switching network environment
Authors: Yokoyama Masaaki , Uose Hisao , Mase Kenichi , Kajiwara Masaichi
Published: July 2007

This paper examines communication media selection control schemes assuming the environment expected in the near future in which users with many kinds of communication media communicate with each other. As the number of communication media increases, the necessity to match the communication medium before the establishment of the communication channel arises in order to reduce the invalid circuit connection caused by the medium mismatch. Assuming the circuit switched network, two medium selection algorithms are proposed: one in which the calling party preassigns the communication medium first (preassign method), and the other in which the calling party inquires about information on the available communication media of the called party (inquiry method). As terminal control schemes, algorithms are proposed which reserve all pertinent terminals while the media selection algorithm is under processing (reservation method), and which do not reserve the terminals (nonreservation method). It is shown that the preassign method is superior to the inquiry method as the medium selection control, and the reservation method is superior to the nonreservation method as the terminal control.
Highly efficient error recovery protocol for satellite link (MN‐SREJ)
Authors: Matsuo Kazunori , Iisaku Shun‐Ichi , Takizuka Takashi , Members Kinji Ono, Regular
Published: July 2007

Data communications over a satellite link makes possible high‐speed data transmission and simultaneous transmission of information to multiple receiving stations. Unless a high‐quality link is provided, the throughput efficiency with the existing HDLC error recovery methods tends to decrease. Therefore, we have developed a new error control scheme (named Multi‐Numbered Selective Reject (MN‐SREJ) method, an improved version of SREJ of HDLC, which would permit high speed and reliable communication even under long propagation delay and poor transmission quality. By the use of MN‐SREJ, more than one solution retransmission request can be made within one round‐trip delay and, furthermore, at the checkpointing, all the unreached frame numbers can be sent to the sending station. The MN‐SREJ method can be expanded easily from point‐to‐point communication to multicast communication, and the degradation of the throughput efficiency as the number of receivers is increased, is small. Furthermore, an approximate formula of the point‐to‐point communication throughput efficiency is derived for an arbitrary maximum number of outstanding frames and round‐trip delay, and the analytical result is shown to coincide well with the simulation result.
An automatic whistler direction finder
Authors: Ohta Kenji
Published: July 2007

From information about the time‐variation of the occurrence number of whistlers and its dispersion, we can estimate the physical information about the electron density at the whistler propagation path in the ionosphere and the magnetosphere plasma and the occurrence of the propagation path. The ionospheric exit point of a whistler is clarified by measuring the magnetic and electric components at one measuring point induced on two mutually orthogonal loop antennas and one vertical antenna by the whistler arrival. Conventional whistler direction finders are not automatic and require operator's manipulation and part exchange. A new whistler direction finder has been developed which has enabled automatic direction finding for whistlers. The equipment consists of the whistler detector using the PLL discriminator, A/D converter, and an 8‐bit microcomputer. High‐accuracy numerical data of 28 whistler waves are stored continuously in 56 Kbyte memories. At a low latitude, the occurrence number of whistlers is small and hence its automatic measurement is indispensable. For this purpose the proposed method provides an effective measurement procedure.
Two‐stepped association procedure and its application to reduction of memory areas of associative memory
Authors: Murakami Kenji , Izumida Masanori , Aibara Tsunehiro
Published: July 2007

This paper proposes a new association scheme (called two‐stepped association scheme) which executes the traditional distributed association scheme in two steps, analyzing its association ability. As an application of this association scheme, a method in the distributed associative memory is proposed which can reduce optimally the size of the memory area for memorizing information to the sense of the least‐mean‐square error. In the two‐stepped association scheme, two‐step associations are performed, which are from the key to the mediate vector and from the mediate vector to the data. The associative process in the associative memory can be made flexible by a suitable selection of the mediate vector. One advantage of the two‐stepped association scheme is that the model acquires a larger degree of freedom in its structure by executing the associative process in two steps. In this paper, this point is utilized and a discussion is made for the condition and the determination of the mediate vector, which leads to the construction of the associative memory with the memory area of specified size and the least mean‐square‐error between the association output and the data. It is verified by a computer simulation that the associative memory constructed in this way can realize the desired associative ability.
A method of interference cancellation in binary PSK coherent receiver
Authors: Segawa Kunio , Nakagawa Masao
Published: July 2007

The wide application of digital radio communication systems in recent years has resulted in increasing demands for allocated frequencies and, due to the overcrowded spectrum, interference has become a crucial problem. In many cases, such interference appears in the upper sideband or in the lower sideband of the useful signal. In the present paper a binary PSK communication system with interference in either the upper or the lower sideband is considered and a method of interference cancellation is proposed for the Costas loop widely used in PSK receivers. Experiments are conducted to demonstrate the efficiency of this method. The results show that the maximum cancellation with a simple circuit added to the Costas loop is 23 dB if Af (the difference between the frequencies of the PSK carrier and the interfering signal) is above 0.3 fβ (fβ the data bit rate). At the same time, the bit error rate in the digital signal is greatly improved. Also, with respect to the impairment due to jitter caused by interference, the performance of the Costas loop is practically unchanged within the specification range of an ordinary Costas loop. The advantages of the present method are that the circuit is simple, it is stable because there is no feedback in the interference cancellation part and the cancellation is effective even for interfering signals of unknown δf.
Relation between instantaneous field of view and recognition performance of thermal imager
Authors: Kondo Michimasa
Published: July 2007

The relation between the instantaneous field of view (IFOV) and recognition performance of a thermal imager is discussed theoretically and a method of improving the target recognition performance applying the relation is presented. When the IFOV included in the evaluation function of the minimum resolvable temperature difference (MRTD) varies, the MRTD does not vary monotonically but has a minimum value. It is found that this value is obtained in the case where the product of the IFOV and target spatial frequency is 0.5. Then the MRTD is defined as the (MRTD)n, and it is shown that (MRTD)IL for various targets is the bottom envelope of MRTD curves for IFOV. Moreover, on the basis of these relations, the condition for obtaining (MRTD)IL by applying zoom optics and changing the IFOV is established and the improvement factor of recognition probability is compared to a fixed IFOV.

The experimental results using a prototype serial scan thermal imager and the calculated values using the theory agree well in their basic characteristics.
Aggregation method using orthogonal vector function and approximation by rational transfer matrices
Authors: Akita Masashi , Hamada Nozomu
Published: July 2007

In recent years, with the widened scope and scale of control, the complexity of systems has been greatly increased and this has motivated studies of methods for reducing the order of systems. The methods presented in this paper employ orthogonal vector functions to reduce the order: (1) the system aggregation method in the time domainand, based on that, (2) the transfer characteristic method in the frequency domain. In (1) orthogonal vector functions are used i in conjunction with the aggregation method which has long been known to have various excellent characteristics. Thus, the characteristics of the aggregation method are retained while deriving a low‐order model such 1 that the squared error of the output is a minimum. Method (2) is shown to be one in which the scalar function approximation method based on orthogonal vector functions (known in the past as the Kautz approximation method) has been generalized to multi‐input/multi‐output systems. Here, also, a least‐square approximation is effected for the transfer function matrix by forming the orthogonal vector functions from the given transfer characteristic.
Hysteresis chaos generator
Authors: Saito Toshimichi
Published: July 2007

This paper discusses the hysteresis generator which is drawing attention as an autonomous chaos generator. However, this generator has not been discussed theoretically for its chaos generation mechanism. A fundamental hysteresis chaos generator is proposed deriving analytically the condition that chaos is generated in the circuit. The analysis of the circuit is performed by mapping procedure, and the Poincare' mapping is derived analytically as a one‐dimensional mapping from the fact that the circuit is a second‐order piecewise‐linear differential equation. By calculating based on the mapping, the generation condition for the chaos is represented explicitly for the parameters In this paper, the definition for the chaos is that the derived mapping has a unique absolutely continuous invariant measure and is ergodic. The generation of the chaos is verified by experiment.
Studies on longitudinal balance measurement in communication systems
Authors: Hagishima Koichi , Koinuma Takeo
Published: July 2007

Induced noises from an ac‐electric train, etc. are applied in common‐phase mode to 2‐wire symmetrical lines. In order to avoid noise quality deterioration by these induced noises, it is important in designing electromagnetic or fully electronic terminating circuits of these lines to obtain an excellent longitudinal balance. Fully electronic equipment, which has been introduced recently to replace electromagnetic equipment in telecommunications systems, e.g., subscriber line circuits in a digital switching system, is different from electromagnetic equipment in that the former has a much lower common‐mode impedance than the latter. This necessitates an optimal longitudinal balance evaluation method appropriate for both fully electronic equipment and electromagnetic equipment. This paper analyzes and evaluates the relation between the longitudinal balance and the noise magnitude of telecommunications equipment, and then clarifies an optimal longitudinal balance evaluation method that is appropriate for telecommunications equipment with arbitrary common‐mode impedance.
Adaptive decoding method for double‐encoding systems
Authors: Imai Hideki , Suda Hirohito , Yashiro Mitsuhiko
Published: July 2007

A general decoding method for doubleencoding systems has been proposed by Imai and Nagasaka, wherein decoding state information obtained in the first stage is utilized fully. This method has a better decoding performance than conventional ones and implementation is easy. However, because this method is based on the probabilistic characteristic of communication channel, its decoding performance can deteriorate when BER of communication channel is varied. This paper proposes an adaptive decoding method which follows the variation of probabilistic characteristic of communication channel. In this method, channel state information can be obtained in the first stage, then the second decoding stage is performed appropriately to that channel state information. With this proposed method, high quality communication is achieved when the communication channel is in good condition. Moreover, even if some quality degradation is unavoidable, communication that is as good as possible is achieved even when the communication channel is in a bad condition. Since an enormous amount of computation is necessary to determine the optimum adaptive decoding system, an adaptive decoding method using some approximation is studied. This method is suitable for a channel where transitions of the channel states can be modeled as a Markov process. Numerical comparisons show that the proposed method achieves a better decoding performance.