Spread spectrum theory and techniques have been studied and developed for commercial applications in Japan, rather than for military use as in USA. Main purpose of the study and development is not to prevent jamming or intentional interference, but to carry out more efficient utilization of available frequency spectra. This paper introduces some spread spectrum theory and techniques which have been studied for the past several years in Japan for improving capacity of transmission. Co-channel interference in code-division multiple access (CDMA) based on spread spectrum technique is the most dominant factor in the limitation of capacity. Various classes of pseudo-noise (PN) sequences or spreading sequences have been proposed in order to reduce co-channel interference or achieve fast acquisition and high security. On the other hand, co-channel interference can be eliminated by digital signal processing approaches, such as adaptive digital filtering and beam-forming. This paper gives an overview of these PN sequences and interference cancellation techniques which appear to be most promising for use in commercial spread spectrum systems.

The magnetic properties, abrasivity, corrosion resistance and electromagnetic characteristics of metal tapes containing acicular CrO2 particles were studied. The following results were obtained; The Bs of tapes decreased with CrO2 addition. The playback output level and noise level decreased, but the C/N level increased, at 4 MHz. The abrasivity of the metal tape was improved by up to 96 % that of commercial oxide tape by adding 50 wt% CrO2. The corrosion resistance of the tape dropped significantly.

This paper shows a heterodyne-typed autocorrelator for direct-sequence spread-spectrum (SS-DS) communications, without using local despreading PN-code and active synchronization circuit. In our proposed autocorrelator, the transmitting SS-DS signal is frequency-converted on every second data by the unique frequency assigned to each user in advance, which is separated not so as to interfere with each other. The received signal is autocorrelated with the delay version and becomes the narrowband signal with the unique centerfrequency. Therefore, our proposed autocorrelator can provide the anti-narrowband interference and random access capability, unlike the conventional autocorrelators.

This letter describes a semi-random searching algorithm for global optimization problems which can reduce the number of objective function evaluations significantly via a deterministic criterion and can find a global optimum via a stochastic criterion. The utility of this algorithm is demonstrated by several examples.

Although the previously proposed indistinctness-degree-glossiness is applicable for a curved surface's specimen, it has fairly large errors by the deviation of specimen from the normal holding position. In order to reduce such the glossiness errors, the convolution was made on the reflected-light-intensity distribution of the specimen by the spatial filter. From its results, a new glossiness Gm was defined and the glossiness errors were reduced to 1/3, compared with the old glossiness errors.

A new glossiness measuring method using the PSD was proposed. This method might be used for the glossiness classification of the specimens such as a high-grade pearls with small gloss-difference, as the substitution of the human visual function.

In this paper we analyze the nonsymmetrically shielded suspended stripline (NSSS) by using the rectangular boundary division method. The characteristic impedance, wavelength reduction factor and attenuation constant of the NSSS are calculated, with special attention to the influence of the thickness of conducting strip. In the thin strip limit our analysis results agree well with those in the literature. When the strip conductor becomes thick enough, howeve, our numerical results show a considerable discrepancy of the propagation characteristics from the thin strip case. Some experimental results on the line capacitance are also presented for a comparison between theory and measurement.

This paper shows a Direct-Sequence Spread-Spectrum (SS-DS) demodulator using block signal processing. One of the difficulties in applying SS-DS techniques to the packet radio network is that each packet needs a long initial-acquisition time for despreading. The acquisition time causes the large degradation of the data transmission efficiency. Our proposed SS-DS demodulator uses the block signal processing, unlike the conventional SS-DS demodulators using real time signal processing. Received signal demodulated quasi-coherently is once stored in memory, and after extracting matched-pulse timing and estimating carrier offset, the signal is demodulated. Incoming data, therefore, are all demodulated without being lost by the initial-acquisition time, and our proposed SS-DS demodulator can provide the higher data transmission efficiency.

This letter considers a problem of realizing an undirected vertex-capacitated network from the view of two types; flow-saturated and flow-unsaturated. As a result, two necessary and sufficient conditions for a given matrix to be realizable as a flow-saturated network and as both a flow-saturated network and a flow-unsaturated one have been shown.

In this paper, we discuss autocorrelation properties of a truncated m-sequence which is used in communication and ranging systems based on a Direct-Sequence Spread Spectrum technique such as Tracking and Data Relay Satellite System (TDRSS) of NASA. A truncated m-sequence is obtained by removing a short part or sequential chips from an original m-sequence. We derive methods to calculate periodic and partial autocorrelation functions of a truncated m-sequence with small complexity. Some constraints for truncated m-sequences which originates in system regulation of TDRSS and its related systems are described. In such systems, partial correlation of a truncated m-sequence is important to achieve fast and stable acquisition. We propose some criteria to select a proper set of truncated m-sequence, and derive the set by using the method to simply calculate correlation.

This letter proposes a new framework for ASIP (Application Specific Integrated Processor) development. The system is called IDEAS (Integrated Design Environment for Application Specific Integrated Processor). IDEAS accepts a set of application programs and its expected data as input, and profiles these programs both statically and dynamically. According to the profiled results, the system decides the architecture of ASIP, and synthesizes the CPU core design of the ASIP, and generates the software development tools for the ASIP such as compiler and simulator.

This paper proposes and analyzes experimentally an SSMA (Spread Spectrum Multiple Access) signal transmission over a high speed QPSK (Quadrature Phase Shift Keying) modulated signal to achieve higher transmission efficiency per transponder and to facilitate a lower power transmitter for SSMA signal transmission. The employment of high-coding-gain forward error correction for SSMA-QPSK signals makes it possible to transmit SSMA-QPSK signals over a non-linearly amplified QPSK signal transmission channel. Experimental results show that under the condition of a 20dB less transmission power assignment to SSMA-QPSK signals than QPSK signals, the QPSK signals achieve only 0.5dB Eb/No degradation (at Pe=110-4) by employing coding-rate seven-eighth FEC, and the SSMA-QPSK signals achieve about 7dB Eb/No degradation (at Pe=110-4) by employing coding-rate one-half FEC. The satellite link budget shows that even if the SSMA-QPSK signal transmission generates about 7dB Eb/No degradation, it requires 20 dB less transmission power and it still has an extra margin of 8.5dB compared with the high speed QPSK signals (total relative gain of 28.5dB). Thus, the proposed system makes it possible to realize one-way digital video signal transmission in QPSK mode and both-way digital voice signal transmission over one transponder for business video communication systems.

This letter describes system architecture of a measurement environment called GINGER that helps programmer productivity by automatically collecting and analyzing data about software development activities. Based on the result of analysis, the environment gives programmers feedback so that they can recognize and improve their activities. The first prototype system of GINGER is currently implemented in a UNIX environment. We expect that the proposed environment will improve the overall productivity of programmers and the quality of resulting products.

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.

Introducing a new analytical method of nonuniform transmission line, this paper shows equivalent transformations between a circuit consisting of a cascade connection of a lumped type E section and a uniform transmission line and one consisting of a cascade connection of a class of nonuniform transmission line and a lumped type E section. Characteristic impedance distribution of these nonuniform transmission lines are expressed as hyperbolic and trigonometric functions. By using the equivalent transformation, it becomes possible to obtain exact network functions of a class of nonuniform transmission lines without solving the telegraph equation.

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.

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.

A new impedance matched film carrier is developed to package uniplanar MMICs. The carrier has an insulating polyimide film on which RF, DC bias, and ground conductive areas are formed. The areas extend into bonding windows, which are etched in the polyimide film, and the extended portions form inner and outer leads. The interconnection of the inner and outer leads to MMIC-electrode pads is highly reliable because of the gold-plated bumps formed at the distal ends of the inner and outer leads. This carrier has an insertion loss of less than 0.2 dB/mm without resonance over the frequency range from DC to 30 GHz. The electrical performance of the GaAs MMIC module with this carrier is almost equal to that of the MMIC measured directly on-wafer.

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.

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.