The difference is investigated between the effects of meaningless and meaningful noise on performance of a task, along with the relevance of the contents of the noise. The extent to which noise content affects task performance is measured and used to set environmental noise assessment. The use of meaningless noise to obscure meaningful noise is also investigated.

This paper considers the problem of realizing excellent performance of rapid acquisition in direct-sequence spread-spectrum communication systems. In this paper, we consider a scheme of digital matched filter (DMF) combined with soft decision function, which has potential capability of improving the characteristics of hard decision function by about 2dB in the environment of additive white Gaussian noise (AWGN) channel and is capable of handling long PN codes by means of simple LSIs. Analysis is made on the performance in the environment of AWGN channel and results of experiments are provided. It is confirmed that the scheme provides attractive means for acquisition of direct-sequence spread-spectrum signals. Namely, soft decision DMF achieves rapid acquisition; the dwell time for soft decision DMF in the process of acquisition is half of that for hard decision DMF. In addition, it is shown that the correlator output signal produced by the acquisition circuit can also be used for the purpose of demodulation; excellent performance of bit error probability is experimentally observed.

This paper reviews in Spread Spectrum Communications in Japan from its birth to the present. The period is divided into three; Birth, Race and Stable Progress Period. A technical overview traces development up to the entrance to the stable progress period, and available references are also given.

Two-dimensional simulations of small-signal parameters (such as transconductance, gate capacitance and cutoff frequency) of GaAs MESFETs are performed in which impurity compensation by deep levels in the semi-insulating substrate is considered. It is shown that these are strongly affected by impurity densities in the substrate. For higher acceptor densities in the substrate, both transconductance and cutoff frequency become higher, because the substrate current is reduced. For low acceptor densities in the substrate, the gate capacitance takes a relatively large value even if the gate voltage is deeply negative, because the channel extends into the substrate and electrons there contribute to the capacitance. It is concluded that to utilize high-frequency performance of GaAs MESFETs, the acceptor densities in the semi-insulating substrate should be made high.

Almost half a century has passed since the first practical use of microwaves in 1940's. During this period, extensive research and development have lead us to steady progress in terms of usable frequencies, fabrication capability of active and passive devices, transmission lines, and device integration density. An overview of this half-century progress in microwaves is presented, and topics of common interest are discussed from the following points of view: (1) Exploiting frontier frequencies from VHF to millimeter-wave and optical frequencies, (2) Transition from vacuum tubes era to solid-state devices era, (3) Transition from waveguides and discrete circuits era to planar integrated circuits era, (4) Wide-ranging applications of microwaves.

LDD-structure GaAs-MESFETs with WSiN bilayer gate are fabricated adopting neutral buried p-layers formed by 50-keV Be-implantation. fT of 108 GHz and fmax of over 130 GHz are obtained on 0.2-µm gate length. A direct-coupled amplifier IC with bandwidth of 10 GHz are fabricated using 0.4 µm GaAs-MESFETs and achieves a high gain of 20 dB with a minimum NF of 3.2 dB with a power consumption of 365 mW. Moreover, a bandwidth of 20 GHz is predicted for the amplifier IC using 0.2-µm GaAs-MESFETs.

We introduce a novel neural network with a trigonometric interconnection called the T-Model neural network in this paper. A VLSI implementation of the T-Model neural network based on CMOS current-mode circuits is also presented. The circuit is completely compatible with standard VLSI technology. A set of neuron-type elements of CMOS current-mode circuits is described and a very large scale neural network is also synthesized. The feasibility and the operation principle of the synthesis of the T-Model neural network using CMOS current-mode circuits are demonstrated and confirmed by experimental results of fabricated CMOS VLSI neural chips.

A novel algorithm based on Kalman filtering is developed for the learning of a layered neural network. The problem of adjusting the weight can be regarded as that of estimating a signal state vector of a linear process. The proposed algorithm, though computationally complex, has an adaptively varying learning rate, while the back-propagation algorithm has constant learning rate. Some experiments conducted for XOR and auto-associative image compression problems have shown that the proposed learning algorithm usually converges in a few iterations and the error is comparable to that of the well-known back-propagation algorithm.

The mappings from multidimension to one-dimension, or the inverse mappings, are theoretically discussed as space-filling curves, i.e., Peano curves. The Peano scan is an application of a Peano curve to the scanning of images, and it is used for analyzing, clustering, or compressing an image, and for limiting the number of the colors used in an image. The horizontal and vertical sizes of the scanned array, however, must be a power of two. To avoid such a case, we generalize the Peano scan for scanning an arbitrarily-sized array, whose horizontal and vertical sizes are possible to be different. First we propose a binary scan which is made of binarily recursive divisions of an image. As the Peano scan is characterized by the statistical property of Brownian motion, further we describe that binary scan can be also optimized to have such statistical property.

A new applicator using a multi-microstrip antenna for hyperthermia is proposed and developed. The applicator consists of semi-cylindrical microstrip elements which serve as non-invasive heating and temperature estimation inside the body. Major advantage of the applicator is that heating and temperature estimation are achieved through only simple switching; The array applicator can heat deep region with surface cooling. Meanwhile the applicator detects an appreciable change in the transmission coefficient of electric field.

A surface mount device (S. M. D.) type miniature isolator has been developed. Its dimension is 6.8 6.9 4 mm3 and weight is 0.75 g. Both the volume and weight have been reduced to one-third compared with a conventional small model. A resin case and metalplated terminals on its surface are used to realize this configuration. By using a simplified simulation technique the most suitable ferrite size and the most suitable magnet are determined to minimize an insertion loss and to realize good temperature stability. Consequently, 0.8 dB insertion loss, 15 dB isolation and 14 dB return loss are obtained within 3 % bandwidth at 836.5 MHz in the practical operating temperature range between -25 and +75. Handling power capability of 2.5 W for forward input and 0.75 W for reverse input are achieved at +25.

This letter considers the problem of approximating and interpolating a two-dimensional (2-dim) signal as the ordinary picture or image signal. We first formulate the problem on the basis of the recent works, and then give a network for the approximation and interpolation. Further, using the network, we present an algorithm for the modeling of a 2-dim signal.

This paper shows the analysis of a multihop Fast Frequency Hopping/Spread Spectrum Multiple Access (FFH/SSMA) System in a selective fading channel, in which we consider the frequency correlation characteristics between the signals on the adjacent hopping frequencies of the desired and intersymbol interference and we also take into account of the effects of interference having close hopping frequencies. A multihop-FFH scheme in which several hopping frequencies are used in order to transmit one data symbol, can be classified into a serialhop-FFH and a parallelhop-FFH scheme. More precise bit error probabilities of the multihop-FFH/SSMA systems are theoretically derived with reducing approximation than the bit error probability corresponding to a conventional analysis using the hit probability. As a result, it is classified that the parallelhop-FFH/SSMA system can achieve the better performance of bit error probability than the singlehop and the serialhop-FFH/SSMA systems in a selective fading channel, while the serialhop-FFH/SSMA system can considerably improve the bit error probability over the singlehop and the parallelhop-FFH/SSMA system in an AWGN channel. The performances depend on the number of simultaneously accessing users. Moreover, the computer simulations confirm the theoretical results.

The Diakoptics (Segmentation) procedure and its application to wideband dispersive absorbing boundary conditions have been implemented in the 3-D TLM method with symmetrical condensed nodes. We show how a microwave structure can be partitioned into substructures which are solved independently and later reassembled, all in the time domain. Frequency dispersive non-TEM boundaries are represented in the time domain by their characteristic impulse response or Johns Matrix. Parasitic reflections due to finite space and time discretization steps have been reduced to less than one percent by exponentially tapering the impulse response of frequency dispersive boundaries, allowing wideband S-parameter extraction from a single impulsive TLM simulation. The S-parameters of some 3-D waveguide discontinuities computed with this technique compare well with the available data.

The recent progress in communication devices has reduced the cost of spread spectrum systems that have been mainly used in the military field, enabling the possibility of using spread spectrum systems for nonmilitary use. Nonmilitary communication networks are classified into two categories: public communication networks and consumer communication networks. At the present, the public communication network share is much larger than that of the consumer communication networks. Both of them will increase; however, the consumer communication network share will be comparable to the public one. The progress of consumer communications is due to inexpensiveness (without charge), user privacy, free design from regulations and advantages of local and small zone communications. To overcome fading, power restrictions, interference and interception is very important for its progress, One of the key technologies of consumer communications is the spread spectrum. Consumer communication networks are characterized by user possession of the network itself in addition to the possession of personal terminals. From the viewpoint of analogy between communication networks and transportation networks, "from public to individual" seems to be today's trend. Several spread spectrum applications for consumer communications in Japan have been introduced as follows: a home security system using power line communication as a wire spread spectrum communication system; a data carrier, a radio remote control, low-power radio systems and a clock rate modulation system as radio spread spectrum communication systems. In addition SAW device applications and digital signal processing applications are introduced.

The coherent electromagnetic wave scattered from a conducting cylinder surrounded by turbulent media is expressed in an analytic form through the two analyses of current characteristics on the cylinder and of wave propagation in random media. Turbulence effects on backscattering characteristics of the coherent wave are made clear numerically for changing the cylinder size and the polarization of incident waves.

We have fabricated a 12 GHz-band monolithic microwave integrated circuit amplifier of which the noise level has been reduced down to 1.18-1.35 dB in the frequency range from 11.7 GHz to 12.7 GHz. The excellent characteristics come from the use of low-gate-resistance, low-equivalent-noise-resistance HEMT's which were obtained by using T-getes, and a hi-lo doping profile in an AlGaAs layer.

In order to evaluate motor function of upper limb in normal and pathological persons, we studied the manual tracking motion whose controlled object is reversal element. We suggest that proposing evaluation parameters reflect clinical symptoms of patients.

This letter describes the waveform relaxation algorithm with the under relaxation technique. This method enables to exploit the multirate behavior, keeping numerical stability. Finally, we apply this algorithm to MOS circuit analysis and verify its availability.