In this paper we propose a two-stage address coding scheme to transmit two data symbols at once within a frame in a MFSK/FH-CDMA system. We compare it with the conventional system using single-stage address coding. Assumed that the address codes of all users are known in the receiver. A multiuser detection scheme is applied and the performance is evaluated by computer simulations to show the improvement in bit error rate (BER) compairing to the conventional system. We also investigate the performance of error-correcting coding and decoding in the two-stage address coded MFSK/FH-CDMA system. An erasure decoding scheme is modified for the two-stage address coded system and is utilized to improve spectral efficiency or to increase user capacity in the MFSK/FH-CDMA system. Finally, we investigate a hybrid scheme of combining the multi-user detection scheme and the error-correcting decoding scheme for the two-stage address coded MFSK/FH-CDMA system. The performance is evaluated by computer simulations.

A 0.15 µm T-shaped gate AlInAs/InGaAs high electron mobility transistor (HEMT) with an excellent RF performance has been developed using selective wet gate recess etching. The gate recess is formed by a pH-adjusted citric acid/NH4OH/H2O2 mixture with an etching selectivity of more than 30 for InGaAs over AlInAs. The standard deviation of saturation drain current (Idss) is as small as 3.2 mA for an average Idss of 47 mA on a 3 inch diameter InP wafer. The etching time for recess formation is optimized and an ft of 130 GHz and an MSG of 10 dB at 60 GHz are obtained. The extremely low minimum noise figure (Fmin) of 0.9 dB with an associated gain (Ga) of 7.0 dB has been achieved at 60 GHz for a SiON-passivated device. This noise performance is comparable to the lowest value of Fmin ever reported for an AlInAs/InGaAs HEMT with a passivation film.

Schnorr's identification scheme is the most efficient and simplest scheme based on the discrete logarithm problem. Unfortunately, Schnorr's scheme is not provably secure, i.e., the security has not been proven to be reducible to well defined intractable problems. Two works have already succeeded to construct provably secure variants of Schnorr's scheme. They have been constructed with a common approach, i.e., by modifying the formula to compute the public key so that each public key has multiple secret keys. These multiple secret keys seem to be essential for their provable security, but also give rise to a penalty in their efficiency. In this paper, we describe a new approach to constructing a provably secure variant, where we never modify the formula, and show that with our approach, we can construct a new efficient provably secure scheme.

A data-base for data compression is universal if in its construction no prior knowledge of the source distribution is assumed and is optimal if, when we encode the reference index of the data-base, its encoding rate achieves the optimal encoding rate for any given source: in the noiseless case the entropy rate and in the semifaithful case the rate-distortion function of the source. In the present paper, we construct a universal data-base for all stationary ergodic sources, and prove the optimality of the thus constructed data-base for two typical methods of referring to the data-base: one is a block-shift type reference and the other is a single-shift type reference.

In this paper, we discuss computational methods for obtaining the bifurcation points and the branch directions at branching points of solution curves for the nonlinear resistive circuits. There are many kinds of the bifurcation points such as limit point, branch point and isolated point. At these points, the Jacobian matrix of circuit equation becomes singular so that we cannot directly apply the usual numerical techniques such as Newton-Raphson method. Therefore, we propose a simple modification technique such that the Newton-Raphson method can be also applied to the modified equations. On the other hand, a curve tracing algorithm can continuously trace the solution curves having the limit points and/or branching points. In this case, we can see whether the curve has passed through a bifurcation point or not by checking the sign of determinant of the Jacobian matrix. We also propose two different methods for calculating the directions of branches at branching point. Combining these algorithms, complicated solution curves will be easily traced by the curve tracing method. We show the example of a Hopfield network in Sect.5.

This paper describes, from a system architectural viewpoint, how knowledge-based technologies have been utilized in developing EXLOG (an LSI circuit synthesis system) and SOFTEX (a software synthesis system) inside the authors' projects. Although the system architectures for EXLOG and SOFTEX started from the same production systems, consisting of transformation rules in the middle of the 1980's, both branched off in different directions in the 1990's. Based on experiences with EXLOG and SOFTEX, the differences between LSI and software design models are discussed, and the future directions are indicated for the knowledge-based design system architectures.

In this paper face feature detection and tracking are discussed, using methods called edge pixel counting and deformable circular template matching. Instead of utilizing color or gray scale information of the facial image, the proposed edge pixel counting method utilizes the edge information to estimate the face feature positions such as eyes, nose and mouth, using a variable size face feature template, the initial size of which is predetermined by using a facial image database. The method is robust in the sense that the detection is possible with facial images with different skin color and different facial orientations. Subsequently, by using a deformable circular template matching two iris positions of the face are determined and are used in the edge pixel counting, to track the features in the next frame. Although feature tracking using gray scale template matching often fails when inter frame correlation around the feature areas are very low due to facial expression change (such as, talking, smiling, eye blinking etc.), feature tracking using edge pixel counting can track facial features reliably. Some experimental results are shown to demonstrate the effectiveness of the proposed method.

A novel series-tapered nonlinear directional coupler is proposed to improve all-optical switching characteristics. Its switching characteristics are analyzed by using a beam propagation method based on the Galerkin's finite element technique. It is presented that the critical power of the series-tapered nonlinear directional coupler is smaller than conventional uniform symmetric and tapered nonlinear directional couplers.

It is known that a family of p-ary bent sequences, whose elements take values of GF (p) with a prime p, possesses low periodic correlation properties and high linear span. Firstly such a family is shown to consist of balanced sequences in the sense that the frequency of appearances in one period is the same for each nonzero element and once less for zero element. Secondly the exact distribution of the periodic correlation values is given for the family.

This paper discusses crystal-growth and device-design issues associated with the development of high-performance InP/InGaAs heretostructure bipolar transistors (HBTs). It is shown that a highly Si-doped n+-subcollector in the HBT structure causes anomalous Zn redistribution during metalorganic vapor phase epitaxial (MOVPE) growth. A thermodynamical model of and a useful solution to this big problem are presented. A novel hybrid structure consisting of an abrupt emitter-base heterojunction and a compositionally-graded base is shown to enhance nonequilibrium base transport and thereby increase current gain and cutoff frequency fT. A double-heterostructure bipolar transistor (DHBT) with a step-graded InGaAsP collector can improve collector breakdown behavior without any speed penalty. We also elucidate the effect of emitter size shrinkage on high-frequency performance. Maximum oscillation frequency fmax in excess of 250 GHz is reported.

With a view to applying to the active matrix displays, micromechanical electrostatic switches having Si-N both-ends-fixed beam of size 1.4 µm by 23 µm grown with LP-CVD on Si wafer were studied about its kinetic switching characteristics, especially its switching speed and hysteresis behavior. Electrostatic beam sticking problems were improved with the additional inverse polarity and short duration pulse following on the turn-on signal. The switching beam deflection of 0.16 µm with the switching time of less than 100 nsec. was measured by tightly focused laser interferometric method. Observed turn-on threshold voltages were more than 30 V, and the on/off hysteresis widths were from one third to two thirds of its threshold voltage. The memory function was experimented for the 2 msec. long holding period with the hold voltage of 25 V following on the writing pulse with the duration of 2 µsec. and the amplitude of 32 V. Now, planarization process has been considered to imtroduce the contact electrodes that were not built-in for these experiments. Although conductive actual switches were not tested, with the obtained results, it seems that the micromechanical electrostatic switch has the large potentials as an active matrix element in display panel especially in electro-luminescent devices or field-emission devices.

We study an asynchronous transfer mode (ATM) multiplexer with selective cell discarding (SCD), and propose as a new traffic parameter the ratio of high and low priority cell streams when a cell stream multiplexed is classified by the cell loss priority (CLP) field in a cell header. By having loss priority control, it is possible to increase the multiplexing gain. For performance analysis we assume that an on-of T bursty traffic is described with several traffic parameters and the proposed priority ratio, and is approximately modeled by a Markov-modulated deterministic process (MMDP). Assuming that several independent and homogeneous on-off bursty traffics with priority discrimination are multiplexed, we present an analytical procedure for the cell loss probability of each priority level in statistical cell multiplexing with loss priority control, and use the performance results for connection admission control (CAC). Also, we consider the effect of the proposed priority ratio. Although loss priority control increases the statistical multiplexing gain, it is not appropriate for the on-off bursty traffic to change the value of the high-priority ratio in order to obtain a larger multiplexing gain, since the admissible load is determined by the loss probability of low priority traffic for most cases and the values of the ratio in a certain range slightly affect it.

This paper presents a theoretically best algorithm within the framework of our image noise model for reconstructing 3-D from two views when all the feature points are on a planar surface. Pointing out that statistical bias is introduced if the least-squares scheme is used in the presence of image noise, we propose a scheme called renormalization, which automatically removes statistical bias. We also present an optimal correction scheme for canceling the effect of image noise in individual feature points. Finally, we show numerical simulation and confirm the effectiveness of our method.

The radiation behavior of a parallel-plate-fed slit in a thick conducting screen is examined. The Fourier transform and the mode-matching technique are used to obtain simultaneous equations for the transmitted field inside the thick conducting screen. The simultaneous equations are solved to represent the transmitted and scattered fiels in simple series forms. The numerical computation is performed to illustrate the behavior of the radiation from the parallel-plate-fed slit. A substantial reduction in the reflection coefficient is possible by choosing a thickness of the conducting screen.

A rat-race hybrid-ring which includes a coupled-line called microwave C-section is proposed for size reduction. The perfect input match, isolation, equal power split and certain phase differences between two output ports can be satisfied at center frequency as in a normal hybrid-ring. The size of the proposed circuit becomes smaller than that of a normal rat-race built up with a folded non-coupled 3/4-wavelength transmission line, although the frequency characteristics are slightly damaged by the electromagnetic coupling between two folded strips. Theoretical results based on the even and odd mode decomposition method are in good agreement with those of the experimental circuit fabricated at 1 GHz.

Multifrequency microwave radiometry has been investigated for non-invasive measurement of temperatures in a human body. In this paper, we propose a new temperature profile model function, which is based on thermo-physiological considerations, for use in model fitting method of retrieving a temperature profile from a set of multifrequency radiometric data. The microwave radiometric technique using the new model function was tested by numerical simulations against animal experiment and clinical data reported elsewhere. The results show that the microwave radiometric technique can be used effectively to measure temperature profiles in tissues over a depth range from 0 to about 4.5 cm.

The purpose of this research is to analyze production rules with coupling modes in active databases and to exploit an assistant system for rule programming. Each production rule is a specification including an event, a condition, and an action. The action is automatically executed whenever the event occurs and the condition is satisfied. Coupling modes are useful to control execution order of transactions. For example, a transaction for consistency check should be executed after transactions for update. An active database, which is a database with production rules, can spontaneously update database states and check their consistency. Production rules provide a powerful mechanism for knowledge-bases. However it is very difficult in general to predict how a set of production rules will behave because of cascading rule triggers, concurrency, and so on. We are attempting to adopt a process algebra as a basic tool to analyze production rules. In order to describe and analyze concurrent and communicating systems, process algebras such as CCS, CSP, ACP, and π-calculus, are well known. However there are some difficulties to apply existing process algebras to analysis of production rules in growing process trees by process creation. In this paper we propose a process algebra named CCSPR (a Calculus of Communicating Systems with Production Rules), Which is an extension of CCS. An advantage of CCSPR is to syntactically describe growing process trees. Therefore, production rules can be appropriately analyzed in CCSPR. After giving definitions and properties of CCSPR, we show an example of analysis of production rules in CCSPR.

The scattering characteristics of a waveguide T-junction with an inductive post are analyzed by the port reflection coefficient method (PRCM), combined with the mode-matching technique. Variation behaviors of the scattering parameters are provided as a function of the operating frequency and the dimensions of the junction. The results are helpful for the design of power dividers using this type of T-junction configuration.

Radio disturbances of digital microwave links are likely to increase as man-made structures screen the radio propagation paths, and unwanted waves reflected or scattered by the structures interfere with radio signals. This paper describes a practical method for evaluating the influence of propagation impairments due to man-made structures on digital microwave links and provides some model calculations of those impairments. Since multilevel and quadrature modulation techniques are employed to achieve high spectral efficiency for recent digital transmissions, not only average level attenuation but also in-band distortion and intersymbol interference have to be taken into account. Propagation distortion, diffraction loss and cross-polar interference due to reflected and scattered waves from man-made structures such as buildings and conductor structures are evaluated.

A novel thick ground plane is proposed as a support for a slot-coupled microstrip antenna and as a heat sink for an MMIC installed on the back plane of the active array antenna. A multi-layer structure of ground planes is also studied for the benefit of easy installation of MMICs. The influence of this thick metal ground plane with a mono- and multi-layer has been investigated in detail. Both measured and calculated results of VSWR and calculated results of the back lobe are shown in detail. The calculated results of VSWR agree well with the measurements. It is made clear that the thickness of the ground plane can be extended to twenty times that of the antenna substrate while maintaining the antenna's performance. An LNA composing an MMIC was developed, attached to the back of the antenna, and operated at 23 GHz. The measured results of this active element agree well with calculated ones and confirm the applicability of the novel design.