In this paper, a new time series analysis method is proposed. The proposed method uses the exponential (EXP) model. The residual signal is assumed to be identically and independently distributed (IID). To achieve accurate and efficient estimates, the parameter of the system model is calculated by maximizing the logarithm of the likelihood of the residual signal which is assumed to be IID t-distribution. The EXP model theoretically assures the stability of the system. This model is appropriate for analyzing signals which have not only poles, but also poles and zeroes. The asymptotic efficiency of the EXP model is addressed. The optimal solution is calculated by the Newton-Raphson iteration method. Simulation results show that only a small number of iterations are necessary to reach stationary points which are always local minimum points. When the method is used to estimate the spectrum of synthetic signals, by using small α we can achieve a more accurate and efficient estimate than that with large α. To reduce the calculation burden an alternative algorithm is also proposed. In this algorithm, the estimated parameter is updated in every sampling instant using an imperfect, short-term, gradient method which is similar to the LMS algorithm.

The paper deals with the level-crossing intervals of a stationary random process. Probability densities of the level-crossing intervals of a process consisting of a sine wave plus Gaussian random noise are experimentally investigated by digital simulation. The Gaussian random noise is selected to be of 7-th order Butterworth power spectrum density. The obtained probability densities appear with a number of isolated peaks much larger than the number observed on the corresponding probability densities of the Gaussian noise alone. When the sine wave frequency is greater than or approximately equal to the half of the cutoff frequency of the noise spectrum, experimental data suggest that each isolated peak has a Gaussian-like density. The mean time interval associated with each Gaussian-like density is equal to a multiple number of the period of the sine wave, while the variance is found to be fairly the same for all peaks of a same probability density. The assumption of "quasi-independence" is not valid for the level-crossing intervals of the present process.

In this article a Neural Network learning scheme is described, which is a generalization of VQ (Vector Quantization) and ART2a (a simplified version of Adaptive Resonance Theory 2). The basic differences between VQ and ART2a will be exhibited and it will be shown how these differences are covered by the generalized scheme. The generalized scheme enables a rich set of variations on VQ and ART2a. One such variation uses the expression ||I||2+||zj||2/||zj||sin(I,zj), as the distance measure between input vector I and weight vector zj. This variation tends to be more robust to noise than ART2a, as is shown by experiments we performed. These experiments use the same data-set as the ART2a experiments in Ref.(3).

The method of estimating multiple sound source locations based on a neural network algorithm and its performance are described in this paper. An evaluation function is first defined to reflect both properties of sound propagation of spherical wave front and the uniqueness of solution. A neural network is then composed to satisfy the conditions for the above evaluation function. Locations of multiple sources are given as exciting neurons. The proposed method is evaluated and compared with the deterministic method based on the Hyperbolic Method for the case of 8 sources on a square plane of 200m200m. It is found that the solutions are obtained correctly without any pseudo or dropped-out solutions. The proposed method is also applied to another case in which 54 sound sources are composed of 9 sound groups, each of which contains 6 sound sources. The proposed method is found to be effective and sufficient for practical application.

A slotted tube resonator (STR) having a shield of conducting circular cylinder which is used as a probe for the magnetic resonance imaging (MRI) is analyzed by using the variational method and the dyadic Green's function of a circular waveguide. Three surface current modes are employed to expand the currents on the STR. Quadruple integrals appearing in the variational expression are evaluated analytically for saving the CPU time. Resonant frequency, Q value and the magnitude of magnetic field distributions for various radii of the shields are obtained to show the effects of the shield. Some measured date are compared with the theoretical results to confirm the validity of the present analysis.

A non-profit satellite communication network is desired to be configured by using low cost earth stations in the field of education, research and health in the Pacific region. This paper proposes the following concept as one of the tools to realize such a network: (a) A hitchhiker transponder dedicated to the network, and (b) The volunteer group prepares earth stations. A preliminary system design shows that the S band hitchhiker payload is most appropriate and has the weight of about 3kg. The feasibility of manufacturing earth stations by a volunteer group is examined through the experiment using ETS-V satellite. The parameters of the hitchhiker payload are re-examined on the basis of the experience of the experiment.

A new optimal nonlinear regulator design method is developed by applying a multi-layered neural network and a fixed point theorem for a nonlinear controlled system. Based on the calculus of variations and the fixed point theorem, an optimal control law containing a nonlinear mapping of the state can be derived. Because the neural network has not only a good learning ability but also an excellent nonlinear mapping ability, the neural network is used to represent the state nonlinear mapping after some learning operations and an optimal nonlinear regulator may be formed. Simulation demonstrates that the new nonlinear regulator is quite efficient and has a good robust performance as well.

The mechanism of environment-dependent self-organization of "positional information" in a coupled nonlinear oscillator system is proposed as a new principle of realtime coordinative control in biological distributed system. By modeling the pattern formation in tactic response of Physarum plasmodium, it is shown that a global phase gradient pattern self-organized by mutual entrainment encodes not only the positional relationship between subsystems and the total system but also the relative relationship between internal state of the system and the environment.

A new bus architecture is proposed for reducing the operating power of future ULSI's. This architecture will relieve the constraint of the conventional supply voltage scaling, which makes it difficult to achieve both high speed and a low standby current if the supply voltage is scaled to less than 2 V. It employs new types of bus driver circuits and bus receiver circuits to reduce the bus signal swing while maintaining a low standby current. The bus driver circuit has a source offset configuration through the use of low-VT MOSFET's and an internal supply voltage corresponding to the reduced signal swing. Bus delay is almost halved with this driver when operated at 0.6-V swing and 2-V supply. The bus receiver circuit has a symmetric configuration with two-level conversion circuits, each of which consists of a transmission gate and a cross-coupled latch circuit. Fast level conversion is achieved without increasing the standby current. The combination of new bus driver and bus receiver enables the bus swing to be reduced to one-third that of the conventional architecture while maintaining a high-speed data transmission and a low standby current. A test circuit is designed and fabricated using 0.3-µm processes. The operation of the proposed architecture was verified, and further improvements in the speed performance are expected by device optimization. The proposed architecture is promising for reducing the operating power of future ULSI's.

The Consultative Committee of Space Data Systems (CCSDS) proposes a packetized telemetry scheme for the convenience of data exchange and networking in space activity. This paper describes the outline of the telemetry scheme and the on-orbit experiment which was carried out to show the applicability of the proposed CCSDS packet telemetry scheme using the Japan's satellite "Hiten" in a highly elliptical orbit. The telemetry data which are generated by the onboard instruments are packetized in Hiten, and reformed to the original data in earth stations successfully. The experimental results show that the standardized scheme is helpful for tracking cross-support between organizations, and that the concatenated code is quite effective to transmit data in a low C/N condition.

It has become an important subject to realize a high-speed D/A converter with low supply voltage. This paper discusses a 10 bit 50 MS/s CMOS D/A converter with 2.7 V power supply. Reduction of the supply voltage is achieved by developing "saturation-linear" biasing technique in current sources. In this scheme, a grounded transistor in cascode configuration is biased in linear region. High conversion rate is obtained by driving this grounded transistor directly. A charging transistor is also introduced into the current source for accelerating the settling time. The D/A converter is fabricated in a 1 µm CMOS process without using optional process steps. It successfully operates at 50 MS/s with 2.7 V power supply. The circuit techniques discussed here can be easily introduced into half-micron D/A converters.

This paper describes new methematical tools, taken from quantum field theory (QFT), which may make it possible to characterize localized excitations (including solitons, but also including chaotic modes) generated by PDE systems. The significance to computer hardware and neurocomputing is also discussed. This mathematics--IF further developed--may also have the potential to reorganize and simplify our understanding of QFT itself--a topic of very great intellectual and practical importance. The paper concludes by describing three new possibilities for research, which will be very important to achieving these goals.

A 155-Mb/s 3232 Si bipolar switch LSI is designed and implemented for a wide application in the broad-band ISDN. The operating speed is 1.4 GHz using an A-BSA Si bipolar process. Its throughput is 5.0 Gb/s by handling four 1.4-GHz interfaces, each of which supports an eight-channel multiplexed data stream. To realize a highly integrated high-speed bipolar LSI, power consumption and chip area should be reduced. Two technologies are newly developed for the LSI, namely, 1) active pull-down circuit with an embedded bias circuit in each gate, and 2) modified standard cell with overlapped cell-channel structure. Using these technologies, total power consumption and chip area are reduced to 60% and 70%, respectively, of what is expected when conventional ECL technologies and standard cell structures are used. The LSI evaluation results show that the developed LSI has sufficient performance to realize a large-scale B-ISDN switching system.

This paper proposes a feedback-loop type transmission power control (TPC) scheme coupled with first and second order prediction methods and analyzes the optimum control period and residual control error. In order to minimize residual control error, the three main factors contributing to residual control error are analyzed. First, to detect accurately up-link rain attenuation, a channel quality detection method is proposed and analyzed experimentally for puseudo-error detection. Second, rain attenuation rates in Ka band are measured and analyzed statistically. Finally, the optimum control period of the proposed TPC scheme is analyzed. The simulation results on the prototype TPC system show a maximum of 4.5 dB residual control error is achievable with an optimum control period of about 1 second to 1.5 seconds.

With the arrival of B-ISDN, point-to-point routing alone is no longer adequate. A new class of computer and video related services, such as mass mailing, TV broadcasting, teleconferencing, and video 900 service, requires the network to handle multiple destination routing (MDR). Multiple destination routing enables widespread usage of multipoint services at a lower cost than networks using point-to-point routing. With this in mind, network providers are researching more into MDR algorithms. However, the MDR problem itself is very complex. Furthermore, its optimal solution, the Steiner tree problem, is NP-complete and thus not suitable for real-time applications. Recently, various algorithms which approximate the Steiner tree problem have been proposed and, in this invited paper, we will summarize the simulation results of these algorithms. But first, we will define the MDR problem, the issues involved, and the benchmark used to compare MDR algorithms. Then, we will categorize the existing MDR algorithms into a five-level classification tree. Lastly, we will present various published results of static algorithms and our own simulation results of quasi-static algorithms.

A priori estimation is presented for a computational complexity of the homotopy method applying to a certain class of strongly monotone nonlinear equations. In the present papers, a condition is presented for a certain class of uniquely solvable equations, under which an upper bound of a computational complexity of the Newton type homotopy method can be a priori estimated. In this paper, a condition is considered in a case of linear homotopy equations including the Newton type homotopy equations. In the first place, the homotopy algorithm based on the simplified Newton method is introduced. Then by using Urabe type theorem, which gives a sufficient condition guaranteeing the convergence of the simplified Newton method, a condition is presented under which an upper bound of a computational complexity of the algorithm can be a priori estimated, when it is applied to a certain class of strongly monotone nonlinear equations. The presented condition is demonstrated by numerical experiments.

The advent of personal data processing and communication, coupled with device miniaturization, has been pushing ULSI's toward lower voltage operation. However, as long as the silicon ULSI circuits are used around room temperature, there will be a limit. Various approaches to reducing the operating voltage will be discussed, with special emphasis placed on device physics, and analog and digital circuit configurations. The low-energy limit is discussed with a comparison to a biological system in order to develop enlightening implications to the future directions.