In this paper, a new encoding/decoding scheme of multiple-valued separable balanced codes is presented. These codes have 2m information digits and m (R - 2) check digits in radices R 4, 2m - 1 information digits and m + 1 check digits in R = 3, where code-length n = Rm. In actual use of code-lengths and radices, it is shown that the presented codes are relatively efficient in comparison with multiple-valued Berger codes which are known as optimal unordered codes. Meanwhile, the optimality of multiple-valued Berger codes is discussed.

One of coupling coefficients appearing in the coupled power equations describing the crosstalk in an image fiber is derived based on the coupled mode theory. Cores arranged in the cross-section of the fiber differ randomly to the degree of several percent in size and consequently modes propagating along the cores differ randomly. Random fluctuations of the propagation constants of modes cause the random transfer process of power between the cores, whereas contributions of the random fluctuations of the mode coupling coefficients to the statistical process can be neglected. The coupling coefficient is described as the ratio of the power transfer ratio to the coupling length for two cores with slightly different radii characterizing the random cores. The theoretical results are in good agreement with measurement results except near cutoff.

This paper proposes a new emphasizing three-dimensional pointing device considering user friendliness and lack of cable clutter. The proposed method utilizes five degrees of freedom via the medium of non-verbal voice of human. That is, the spatial direction of the sound source, the type of the voice phoneme and the tone of the voice phoneme are utilized. The input voice is analyzed regarding the above factors and then taking proper effects as previously defined for human interface. In this paper the estimated spatial direction is used for three-dimensional movement for the virtual object as three degrees of freedom. Both of the type and the tone of the voice phoneme are used for remaining two degrees of freedom. Since vocalization of nonverbal human voice is an everyday task, and the intonation of the voice can be quite easily and intentionally controlled by human vocal ability, the proposed scheme is a new three-dimensional spatial interaction medium. In this sense, this paper realizes a cost-effective and handy nonverbal interface scheme without any artificial wearing materials which might give a physical and psychological fatigue. By using the prototype the authors evaluate the performance of the scheme from both of static and dynamic points of view and show some advantages of look and feel, and then prospect possibilities of the application for the proposed scheme.

This letter presents a new design method for approximate inverse systems using all-pass networks. The efficacy of approximate inverse systems for input and parameter estimation of nonminimum phase systems is well recognized. in the previous methods, only time domain design of FIR (finite impulse response) type approximate inverse systems were considered. Here, we demonstrate that IIR (infinite impulse response) type approximate inverse systems outperform the previous methods. A nonlinear optimization technique is adopted for designing the proposed system in the frequency domain. Numerical examples are also presented to show the effectiveness of the proposed method.

This letter describes an efficient and economical method for dropping optical fiber to residential premises in which several fiber ribbons in a distribution cable are assigned to one dropping point. The optical fiber cables for dropping, which contain mono-coated fibers, are then aerially installed between several poles from this point during initial construction. One or two fibers in a cable are then branched and dropped to a subscriber when the demand arises. When an optical drop wire stranded cable is used as the optical fiber cable for dropping, the above method can be employed without the need for a fiber joint in the dropping portion. The tube stranding pitch of this cable is investigated theoretically and experimentally, and the cable is manufactured based on the results. The transmission characteristics of the cable are confirmed to be stable.

In this letter, a novel current-mode operational amplifier (COA) is proposed. The proposed COA can operate at 2 V (1 V) supply voltage. For high frequency operation it has only an npn transistor in signal path. Finally, SPICE simulation are shown to verify the performance of the proposed COA.

This work addresses the problems of bit allocation and coding gain in subband coding system with non-paraunitary filter banks. Since energy conservation does not hold in non-paraunitary filter banks, the model to be adopted for quantizers is important to evaluate the output distortion introduced by subband signal quantization. To evaluate the overall distortion we start with adopting the gain plus additive noise model for quantizers, which is more reliable than the additive noise model. With this model, the expression for overall reconstruction error variance becomes so complicated that the problem of optimum bit allocation, as required for evaluation of the coding gain, must be numerically solved. So, we propose an approximation method in which we neglect the terms due to correlation among quantization errors in calculating the bit allocation but take them into consideration in evaluating the coding gain, assuming sufficiently high bitrate coding. Application of this approximation method to the SSKF subband coding systems with AR (1) input source shows that the method is very accurate even at low bit rate coding (1 bit/sample).

An architecture for a high-density nonvolatile memory with ferroelectric capacitors is proposed and simulated. The architecture includes: (1) the operation procedure for DRAM-like memory cells with a Vcc/2 common plate, (2) commands and pin arrangement compatible with those of DRAMs. The resulting ferroelectric memory is expected to show, in addition to nonvolatility, high performance in terms of speed, active power dissipation, and read endurance. In addition, the memory can be handled in the same way as DRAMs. The proposed basic operations are confirmed by using circuit simulations, in which an equivalent circuit model for ferroelectirc capacitors is incorporated. A problem remaining with the architecture is low write endurance due to fatigue along with polarization switching. Designing the reference-voltage generator for 1T1C (one-transistor and one-capacitor) cells, while considering signal reduction along with fatigue, will be another issue for achieving high-density comparable to that of DRAMs.

The electrical characteristics of sealed CMOSFETs with gates crossing sources/drains at 90 and 45 are experimentally investigated using test devices fabricated by an n-well CMOS process with trench isolation. Gain factors of surface-channel 90 and 45 n-MOSFETs can be estimated by a simple correction theory based on the combination of a center MOSFET and two edge MOSFETs. However, relatively large departures from the theory are observed in buried-channel 90 and 45 p-MOSFETs with widths less than the channel length. The difference between n- and p-MOSFETs is mainly due to the channel type. Other basic device parameters such as saturation drain currents, threshold voltages, subthreshold swings, maximum substrate currents and substrate-voltage dependence of threshold voltages are also measured and qualitatively explained.

In this paper, we give a direct proof of the result of Latteux and Turakainen that the full class of recursively enumerable languages can be obtained from minimal linear languages (which are generated by linear context-free grammars with only one nonterminal symbol) by Dyck reductions (which reduce pairs of parentheses to the empty word).

In this study, we discuss a discrete-time cellular neural network (DTCNN) and its applications including convergence property and stability. Two theorems about the convergence condition of nonreciprocal non-uniform DTCNNs are described, which cover those of reciprocal one as a special case. Thus, it can be applied to wide classes of image processings, such as associative memories, multiple visual patterns recognition and others. Our DTCNN realized by the software simulation can largely reduce the computational time compared to the continuous-time CNN.

A novel circuit design technique for bipolar linear transconductance amplifiers is presented. A triple-tail cell, which consists of three emitter-common transistors biased by a single tail current, is exchangeable with an emitter-coupled pair in the multi-tanh cell, such as a multi-tanh doublet, a multi-tanh triplet or a multi-tanh quad. Therefore, the multi-tanh technique is further theoretically expanded to the super-multi-tanh technique. In this paper, the super-multi-tanh technique is proposed and discussed, and furthermore, a super-multi-tanh doublet is verified with bipolar transistor-arrays and discrete resistors on a breadboard.

According as the fine LSI process technique develops, the technique to reduce power dissipation of high-frequency integrated analog circuits is getting more important. This paper describes a design of high-frequency integrator with low power dissipation for monolithic leapfrog filters. In the design of the conventional monolithic integrators, there has been a great dfficulty that a high-frequency integrator which can operate at low supply voltage cannot be realized without additional circuits, such as unbalanced-to-balanced conversion circuits and common-mode feedback circuits. The proposed integrator is based on the Miller integrator. By a PNP current mirror circuit, high CMRR is realized. However, the high-frequency characteristic of the integrator is independent of PNP transistors. In addition, it can operate at low supply voltage. The excess phase shift of the integrator is compensated by insertion of the compensation capacitance. The effectiveness of the proposed technique is confirmed by PSPICE simulation. The simulation results of the integrator shows that the common-mode gain is efficiently low and the virtual ground is realized, and that moderate phase compensation can be achieved. The simulation results of the 3rd-order leapfrog filter using the integrator shows that the 50 MHz-cutoff frequency filter is obtained. Its power dissipation in operating 2 V-supply voltage is 5.22 mW.

The present paper is concerned with an algorithm for the minimization of multiple-valued input, binary-valued output functions. The algorithm is an extension to muitiple-valued logic of an algorithm for the minimization of ordinary single-output Boolean functions. It is based on a local covering approach. Basically, it uses a "divide and conquer" technique, consisting of two steps called expansion and selection. The present algorithm preserves two important features of the original one. First, a lower bound on the number of prime implicants in the minimum cover of the given function is furnished as a by-product of the minimization. Second, all the essential primes of the function are identified and selected during the expansion process. That usually improves efficiency when handling functions with many essential primes. Results of a comparison of the proposed algorithm with the program ESPRESSO-IIC developed at Berkeley are presented.

In previous papers the building of hierarchical networks made up of components using fuzzy rules was presented. It was demonstrated that this approach could be used to construct networks to solve classification problems, and that in many cases these networks were computationally less expensive and performed at least as well as existing approaches based on feedforward neural networks. It has also been demonstrated how this approach could be extended to real-valued problems, such as function approximation and time series prediction. This paper investigates the problem of choosing the best network for real-valued approximation problems. Firstly, the nature of the network parameters, how they are interrelated, and how they affect the performance of the system are clarified. Then we address the problem of choosing the best values of these parameters. We present two model selection tools in this regard, the first using a simple statistical model of the network, and the second using structural information about the network components. The resulting network selection methods are demonstrated and their performance tested on several benchmark and applied problems. The conclusions look at future research issues for further improving the performance of the clustering network.

In CRYPTO '94, Langford and Hellman attacked DES reduced to 8-round in the chosen plaintext scenario by their "differential-1inear cryptanalysis," which is a combination of differential cryptanalysis and linear cryptanalysis. In this paper, a historical review of differential-linear cryptanalysis, our formalization of differential-linear cryptanalysis, and the application of differential-linear cryptanalysis to FEAL-8 are presented. As a result, though the previous best method (differential cryptanalysis) required 128 chosen plaintexts, only 12 chosen plaintexts are sufficient, in computer experimentations, to attack FEAL-8.

This paper describes the performance of a predistorter implementation to a superluminescent diode (SLD) in fiber-optic wireless systems under the optical reflection. SLD intensity noise and 3rd-order intermodulation distortion (IM3) are experimentally compared with those of DFB-and FP-LD. It is observed that the IM3 of SLD has ideal 3rd characteristics and output noise remains unchanged against the number of optical connectors. It is also found that the predistorter reduces IM3 by 8 dB. Receiver sensitivity of the system is discussed from the view point of overall design. the BER performance of an SLD with predistorter using a π/4-QPSK signal as a subcarrier is also described theoretically and experimentally.

In this paper, we propose to use graded-index multimode fibers (GI-MMFs) with Fabry-Perot laser diodes (FP-LDs) for short-span and low-cost feeders. The multimode fiber feeders can be applied to wireless personal communication systems where the required feeder length is within several hundred meters, such as distributed antenna networks for microcellular systems or wireless LANs. The use of multimode fibers makes fiber coupling and connection easier, and has the potential to greatly reduce total system cost. Three types of GI-MMFs are considered as transmission media, (1) silica-based glass optical fiber (GI-GOF),(2) silica-core plastic-clad fiber (GI-PCF), and (3) all-plastic optical fiber (GI-POF). It is shown that GI-GOF and GI-PCF are suitable for use as feeders in the microcells of CDMA cellular and wireless LAN systems within 300m in length. GI-POF is estimated to be suitable for use as feeders in wireless LANs within 100m in length. A multimode fiber feeder with FP-LDs and GI-PCF of 300 m is developed in order to demonstrate its applicability to a wireless LAN system operating in the 2.4 GHz ISM band.

We describe the design, fabrication, and characteristics of a push-pull type ridged Ti:LiNbO3 optical modulator with two electrodes. The structure keeps microwave propagation loss low and enables a large interaction between microwaves and optical waves under the condition of velocity and impedance matching, resulting in a large modulation bandwidth and low driving voltage. Using this structure, we have developed an optical intensity modulator with an optical 3-dB bandwidth of 45 GHz (an electrical 3-dB bandwidth of 30 GHz) and a half-wave voltage of 3.9 V in single-electdoe operation (a half-wave voltage of 1.95 V in push-pull operation)at a wavelength of 1.55µm.

External modulators, which have smaller chirping characteristics than laser diode direct modulation, are desired for high-speed and long-distance optical fiber communication systems. This paper reviews semiconductor and Ti:LiNbO3 guided-wave high-speed optical modulators. Since several effects exist for semiconductor materials, various kinds of semiconductor optical modulators have been investigated. Among these, absorption type intensity modulators based on Franz-Keldysh effect in bulk materials and quantum confined stark effect in multiple quantum well materials, are promising because of compactness, low drive voltage nature and integration ease with DFB lasers. Recent progress on semiconductor absorption modulators and DFB-LD integrated semiconductor modulators is discussed with emphasis on a novel fabrication method using selective area growth by MOVPE (Metal Organic Vapor Phase Epitaxy). The Ti:LiNbO3 optical modulators are also important, due to the advantage of superior chirping characteristics and wide bandwidth. Since the Ti:LiNbO3 optical modulator has low propagation loss and low conductor loss natures for optical waves and microwaves, respectively, the traveling-wave electrode configuration is suitable for high-speed operation. Here, broadband Ti:LiNbO3 optical modulators are discussed with emphasis on traveling-wave electrode design.