Full scan design of sequential circuits results in greatly reducing the cost of their test generation. However, it introduces the extra expense of many test clocks to control and observe the values of flip-flops because of the need to shift values for the flip-flops into the scan panh. In this paper we propose a new method of generating compact test sequences for scan-based sequential circuits on the assumption that the number of shift clocks is allowed to vary for each test vector. The method is based on Boolean function manipulation using a shared binary decision diagram (SBDD). Although the test generation algorithm is basically for general sequential circuits, the computational cost is much lower for scan-based sequential circuits than for non-scanbased sequential circuits because the length of a test sequence for each fault is limited. Experimental results show that, for all the tested circuits, test sequences generated by the method require much smaller number of test clocks than compact or minimum test sets for combinational logic part of scan-based sequential circuits. The reduction rate was 48% on the average in the experiments.

Logic synthesizers usually have good area minimization capabilities, producing circuits of minimal area. But good delay minimization techniques are still missing in current logic synthesis technology. In [7], the RENO algorithm (which stands for REsynthesis for Network Optimization) was proposed for minimizing the area of multi-level combinational networks, and its effectiveness in designing minimal-area networks has been demonstrated. In this paper, we present improvements and extensions of the RENO algorithm for network delay minimization by using Boolean resynthesis techniques. We will discuss new algorithms for gate resynthesis which have not only reduced the processing time significantly, but also have improved the quality of minimization. Due to the generality of the gate resynthesis algorithms, we can minimize both delay and area of a network concurrently in a unified way, and network delay is reduced significantly with no or very small area penalty. Extensive experimental results and comparison with the speed_up algorithm in SIS-1.0 are presented.

A new arithmetic multiple-valued algebra with functional completeness is introduced. The algebra is called Neuro-Algebra for it has very similar formula and architecture to neural networks. Two canonical forms of multiple-valued functions of this Neuro-Algebra are presented. Since the arithmetic operations of the Neuro-Aglebra are basically a weighted-sum and a piecewise linear operations, their implementations are very simple and straightforward. Furthermore, the multiple-valued networks based on the Neuro-Algebra can be trained by the traditional back-propagation learning algorithm directly.

An asynchronous spread spectrum (SS) wireless modem has been implemented using an efficient ZnO-SiO2-Si surface acoustic wave (SAW) convolver. The modem is based on a direct-sequence/frequency-shift-keying (DS/FSK) method for the modulation. The demodulation is carried out asynchronously utilizing the coherent correlation characteristics of the SAW convolver. In order to improve the narrowband interference rejection capability, we propose a new technique based on the reference signal control. A notched-reference-signal circuit and a self-convolution canceler are implemented in the SS modem for the reference signal control. It was found that the antijam capability for narrowband interference is at least -24dB of desired-to-undesired power ratio (D/U); the improvement of the antijam capability is 16dB up as compared with our previous SS modem.

This paper proposes M-ary/SSMA using co-channel interference cancellation techniques and presents comparisons with conventional DS/SSMA and other systems. First, ideal models of DS/SSMA and M-ary/SSMA using co-channel interference cancellation techniques are analyzed. In the cancellation circuit of DS/SSMA, when an error bit of other user's data arises, the received signal is degraded by "voltage addition" of the error sequence. While, in M-ary/SSMA, it is degraded by only "power addition" of the error code. Therefore, though the circuits are complicated, bit error rate of the proposed system can be improved considerably. Further, improvement of spectral efficiency in these systems are shown for several bit error rate and chip waveforms.

This letter presents a new algorithm for echo cancellers, which prevents the reduction of echo return loss due to a double-talk. The essence of the algorithm is to introduce signal delays to avoid the reduction. A convergence condition in the algorithm was examined by using the IIR filter expression of the NLMS algorithm, and it was concluded that the IIR filter should be a low pass filter with unity gain. The condition is accomplished by selecting a small step gain.

An automatic tap assignment method in sub-band adaptive filter is proposed in this letter. The number of taps of the adaptive filter in each band is controlled by the mean-squared error. The numbers of taps increase in the bands which have large errors, while they decrease in the bands having small errors, until residual errors in all the bands become the same. In this way, the number of taps in a band is roughly proportional to the length of the impulse response of the unknown system in this band. The convergence rate and the residual error are improved, in comparison with existing uniform tap assignment. Effectiveness of the proposed method has been confirmed through computer simulation.

Behavior of solutions related to an accuracy exp(-1/ε) is studied. Computer results are given, and examined from the view-point of non-standard analysis. The experimental results raise some important questions on the computer study of slow-fast systems.

This paper proposes a superposed SSMA (Spread Spectrum Multiple Access)-QPSK (Quadrature Phase Shift Keying) signal transmission scheme over high speed QPSK signals to achieve higher frequency utilization efficiency and to facilitate lower power transmitters for SSMA-QPSK signal transmission. Experimental results show that the proposed scheme which employs the coding-rate of one-half FEC (Forward Error Correction) and a newly proposed co-channel interference cancellation scheme for SSMA-QPSK signals can transmit twenty SSMA-QPSK channels simultaneously over a nonlinearly amplified high speed QPSK signal transmission channel and achieve as ten times SSMA channels transmission as that without co-channel interference cancellation when the SSMA-QPSK signal power to the high speed QPSK signal power ratio equals -30dB. Moreover, cancellation feasibility generation of the interference signals replica through practical hardware implementation is clarified.

The Hilbert curve is one of the simplest curves which pass through all points in a space. Many researchers have worked on this curve from the engineering point of view, such as for an expression of two-dimensional patterns, for data compression in an image or in color space, for pseudo color image displays, etc. A computation algorithm of this curve is usually based on a look-up table instead of a recursive algorithm. In such algorithm, a large memory is required for the path look-up table, and the memory size becomes proportional to the image size. In this paper, we present an implementation of a fast sequential algorithm that requires little memory for two and three dimensional Hilbert curves. Our method is based on some rules of quad-tree traversal in two dimensional space, and octtree traversal in three dimensional space. The two dimensional Hilbert curve is similar to the scanning of a DF (Depth First) expression, which is a quad-tree expression of an image. The important feature is that it scans continuously from one quadrant, which is obtained by quad tree splitting, to the next adjacent one in two dimensional space. From this point, if we consider run-lengths of black and white pixels during the scan, the run-lengths of the Hilbert scan tend to be longer than those of the raster scan and the DF expression scanning. We discuss the application to data compression using binary images and three dimensional data.

Practical linewidth measurement accuracy better than 0.02 µm 3 sigma that meets the production requirement for devices with sub-half micron features, was achieved in a field emission scanning electron-beam metrology system (Hitachi S-7000). In order to establish high accuracy linewidth measurement, it was found in the study that reduction of electron-beam diameter and precise control of operating conditions are significantly effective. For the purpose of reducing electron-beam diameter, a novel electron optical system was adopted to minimize the chromatic aberration which defines electron-beam profile. As a result the electron beam diameter was reduced from 20 nm to 16 nm. In order to reduce measurement uncertainties associated with actual operating conditions, a field emission electron gun geometry and an objective lens current monitor were investigated. Then the measurement uncertainties due to operating conditions was reduced from 0.016 µm to 0.004 µm.

In this paper, we will define Kleene-Stone logic functions which are functions F: [0, 1]n[0, 1] including the intuitionistic negation into fuzzy logic functions, and they can easily represent the concepts of necessity and possibility which are important concepts of many-valued logic systems. A set of Kleene-Stone logic functions is one of the models of Kleene-Stone algebra, which is both Kleene algebra and Stone algebra, as same as a set of fuzzy logic functions is one of the models of Kleene algebra. This paper, especially, describes some algebraic properties and representation of Kleene-Stone logic functions.

This paper proposes fiber optic link configurations for use in microwave and millimeter-wave transmission Higher frequencies,such as millimeter-waves, are well suited to transmission of broadband signals. Photodiodes can operate simultaneously as optical detectors and microwave frequency mixers thanks to their inherent nonlinearities. This allows us to increase the output radio frequncy. But, this also generates undesired spurious frequencies, necessitating the use of microwave filters. We discuss here two fiber optic link configurations, i.e., balanced/image canceling photodiode mixing links utilizing the combination of microwave functional components and optical devices to suppress the local/image frequency without filters. These configurations are experimentally investigated at microwave frequencies and local/image frequency suppression is successfully demonstrated.

We propose a direct-sequence spread-spectrum multi-access (DS/SSMA) receiver that incorporates multipath diversity combining and multistage co-channel interference (CCI) cancellation. This receiver structure which is more resistant to the near/far problem essentially removes more and more of the CCI with each successive cancellation stage. With the assumption that perfect channel estimates have been obtained, we analyze the bit error rate (BER) performance of this system when received powers are unequal. Results show that the BER can approach that of a single-user case as the number of CCI cancellation stages increases.

This paper relates to a novel algorithm for fast estimation of the coefficients of the adaptive FIR filter. The novel algorithm is derived from a first order IIR filter experssion clarifying the estimation process of the NLMS (normalized least mean square) algorithm. The expression shows that the estimation process is equivalent to a procedure extracting the cross-correlation coefficient between the input and the output of an unknown system to be estimated. The interpretation allows to move a subtraction of the echo replica beyond the IIR filter, and the movement gives a construction with the IIR filter coefficient of unity which forms the arithmetic mean. The construction in comparison with the conventional NLMS algorithm, improves the covergence rate extreamly. Moreover, when we use the construction with a simple technique which limits the term of calculating the correlation coefficient in the beginning of a convergence process, the convergence delay becomes negligible. This is a very desirable performance for acoustic echo canceller. In this paper, double-talk and echo path fluctuation are also studied as the first stage for application to acoustic echo canceller. The two subjects can be resolved by introducing two switches and delays into the evaluation process of the correlation coefficient.

An acoustic echo canceller that also cancels room noise is proposed. This system has an additive (noise reference) input port, and a noise canceller (NC) precedes the echo canceller (EC) in a cascade configuration. The adaptation control problem for the cascaded echo and noise canceller is solved by controlling the adaptation process to match the occurrence of intermittent speech/echo; the room noise is a stationary signal. A simulation shows that adaptation using the NLMS algorithm is very effective for the echo and noise cancellation. Sub-band cancelling techniques are utilized. Noise cancellation is realized with a lower band EC. Hardware is implemented and its performance evaluated through experiments under a real acoustic field. The combination of the EC with NC maintains excellent performance at all echo to room noise power ratios. It is shown that the proposed canceller overcomes the disadvantages traditionally associated with ECs and NSc.

This paper proposes a new adaptive algorithm for acoustic echo cancellers with four times the convergence speed for a speech input, at almost the same computational load, of the normalized LMS (NLMS). This algorithm reflects both the statistics of the variation of a room impulse response and the whitening of the received input signal. This algorithm, called the ESP (exponentially weighted step-size projection) algorithm, uses a different step size for each coefficient of an adaptive transversal filter. These step sizes are time-invariant and weighted proportional to the expected variation of a room impulse response. As a result, the algorithm adjusts coefficients with large errors in large steps, and coefficients with small errors in small steps. The algorithm is based on the fact that the expected variation of a room impulse response becomes progressively smaller along the series by the same exponential ratio as the impulse response energy decay. This algorithm also reflects the whitening of the received input signal, i.e., it removes the correlation between consecutive received input vectors. This process is effective for speech, which has a highly non-white spectrum. A geometric interpretation of the proposed algorithm is derived and the convergence condition is proved. A fast profection algorithm is introduced to reduce the computational complexity and modified for a practical multiple DSP structure so that it requires almost the same computational load, 2L multiply-add operations, as the conventional NLMS. The algorithm is implemented in an acoustic echo canceller constructed with multiple DSP chips, and its fast convergence is demonstrated.

This paper proposes a new adaptive algorithm of the FIR type digital filter for an acoustic echo canceller and similar application fields. Unlike an echo canceller for line, an acoustic echo canceller requires a large number of taps, and it must work appropriately while it is driven by colored input signal. By controlling the filter tap length and updating filter coefficients multiple times during a single sampling interval, the proposed algorithm improves the convergence characteristics of adaptation even if colored input signal is introduced. This algorithm is maned VT-LMS after variable tap length LMS. The results of simulation show the effectiveness of the proposed algorithm not only for white noise but also for colored input signal such as speech. The VT-LMS algorithm has better convergence characteristice with very little extra computational load compared to the conventional algorithm.

This paper presents a method for LSI implementation of a long-tap acoustic echo canceller algorithm using the residue number system (RNS) and the mixed-radix number system (MRS). It also presents a quantitative comparison of echo canceller architectures, one using the RNS and the other using the binary number system (BNS). In the RNS, addition, subtraction, and multiplication are executed quickly but scaling, overflow detection, and division are difficult. For this reason, no echo canceller using the RNS has been implemented. We therefore try to design an echo canceller architecture using the RNS and the NLMS algorithm. It is shown that the echo canceller algorithm can be effectively implemented using the RNS by introducing the MRS. The quantitative comparison of echo canceller architectures shows that a long-tap acoustic echo canceller can be implemented more effectively in terms of chip size and power dissipation by the architecture using the RNS.

The increase of surface microroughness on Si substrate degrades the electrical characteristics such as the dielectric breakdown field intensity (EBD) and charge to break-down (QBD) of thin oxide film. It has been found that the surface microroughness increases in the wet chemical process, particularly in NH4OH-H2O2-H2O cleaning (APM cleaning). It has been revealed that the surface microroughness does not increase at all if the NH4OH mixing ratio in NH4OH-H2O2-H2O solution is reduced from the conventional level of 1:1:5 to 0.05:1:5, and the room temperature ultrapure water rinsing is introduced right after the APM cleaning. At the same time, the APM cleaning with NH4OH-H2O2-H2O mixing ratio of 0.05:1:5 has been very effective to remove particles and metallic impurities from the Si surface. The surface microroughness dominating the electrical properties of very thin oxide films is strictly influenced by the wafer quality. The increase of surface microroughness due to the APM cleaning has varied among the wafer types such as Cz, FZ and epitaxial (EPI) wafers. The increase of surface microroughness in EPI wafer was very much limited, while the surface microroughness of FZ and Cz wafers gradually increase. As a result of investigating the amount of diffused phosphorus atoms into these wafers, the increase of the surface microroughness in APM cleaning has been confirmed to strongly depend on the silicon vacancy cluster concentration in wafer. The EPI wafer having low silicon vacancy concentration is essentially revealed superior for future sub-half-micron ULSI devices.