The performance of direct-detection optical synchronous code-division multiple-access (CDMA) systems using pulse position modulation (PPM) signaling (PPM/CDMA) with interference canceller is analyzed. In optical CDMA systems, it is known that the maximum number of simultaneous users in CDMA systems is limited by the maximum tolerable interference among users. If the receiver is able to estimate this interference and cancel or reduce its effect, the capacity of CDMA systems can be increased and the system performance can be improved. There are some ways to increase the system performance, that is, using PPM and interference canceller. However, the system using both PPM and interference canceller has not been analyzed. In this paper, the upper bound on the bit error probability of optical synchronous PPM/CDMA systems with interference canceller is derived, and the bit error probability of optical synchronous PPM/CDMA systems is evaluated under the assumption of number-state light field where the background noise is negligible. We compare the bit error probability of the optical synchronous PPM/CDMA systems with interference canceller to that of the optical synchronous PPM/CDMA systems without interference canceller and to those of optical synchronous OOK/CDMA systems with and without interference canceller. We show that optical synchronous PPM/CDMA systems with interference canceller have better bit error probability performance.

We studied effects of 50-200-keV electrons on semiconductor devices using BEASTLI (backscattered electron assisting LSI inspection) method. When irradiating semiconduc-tor devices with such high-energy electrons, we have to note two phenomena. The first is surface charging and the second is device damage. In our study of surface charging, we found that a net positive charge was formed on the device surface. The positive surface charges do not cause serious influence for observation so that we can inspect wafers without problems. The positive surface charging may be brought about because most incident electrons penetrate the device layer and reach the conducting substrate of the semiconductor device. For the device damage, we studied MOS devices which were sensitive to electron-beam irradiation. By applying a 400- annealing to electron-beam irradiated MOS devices, we could restore the initial characteris-tics of MOS devices. However, in order to recover hot-carrier degradation due to neutral traps, we had to apply a 900- annealing to the electron-beam irradiated MOS devices. Thus, BEASTLI could be successfully used by providing an apporopri-ate annealing to the electron-beam irradiated MOS devices.

We present a new method to cancel interfering sinusoidal signals. In this method, the Interpolated FFT (IpFFT) algorithm is used to estimate the parameters of the interference signal: frequency, amplitude and phase. The cancellation is then performed in the time domain. In order for the IpFFT to perform reliably, accurate spectral information about the interference signal is needed. Since, the information signal masks the interference signal, it becomes difficult to estimate the parameters of the interference signal. To alleviate this masking effect, two techniques are discussed here. These techniques involve frame update of interference spectral information of the interference signal, and adaptive averaging. Significant improvement over conventional frequency domain filterings is achieved. The price paid is only little, beyond the computation of the FFT. Comparison with the conventional frequency domain filter shows that our system has approximately 5dB better cancellation capability for a single interfering signal.

This paper describes a CDMA cellular system based on adaptive interference cancellation (CDMA-AIC) with a large capacity. In the CDMA-AIC, each base station employs a single-user type adaptive interference canceller (AIC), which consists of a fractionally chip-spaced code-orthogonalizing filter (COF) and a coherent detector. The AIC adaptively removes power-dominant multiple-access interferences (MAIs) in the cellular system, regardless of whether they are intra-cell interferences or inter-cell interferences, without any information about them, such as spreading codes, signal received timings and channel parameters. Evaluation under the multiple-cell environment demonstrates that the reverse link capacity of the CDMA-AIC with QPSK modulation is 3.6 times as large as the capacity of the CDMA without MAI cancellation. Further, the capacity is less sensitive to transmission power control errors than that of the conventional CDMA systems.

Co-channel interference is a major factor limiting spectral efficiency of a cellular radio system. The trellis-coded co-channel interference canceller (TCC) leading to the significant increase of traffic capacity of a cellular system has been proposed. In this scheme, a maximum-likelihood sequence estimation implemented with the Viterbi algorithm is extended to estimate both desired signal and co-channel interference, and combined with trellis-coded modulation to enhance the co-channel interference cancelling capability. The complexity of TCC grows exponentially with the channel memory and the constraint length of the trellis encoder. In this paper, two reduced-state sequence estimation algorithms, namely, the delayed decision feedback sequence estimation and the M-algorithm, are applied to TCC and their performance is compared. In addition, effective trellis coded modulation schemes to reduce the computational complexity are proposed. The performance of these schemes is examined through simulations, and compared to that of a conventional interference canceller.

An adaptive algorithm for a single sinusoid detection using IIR bandpass filter with parallel block structure has been proposed by Nishimura et al. However, the algorithm has three problems: First, it has several input frequencies being impossible to converge. Secondly, the convergence rate can not be higher than that of the scalar structure. Finally, it has a large amount of computation. In this paper, a new algorithm is proposed to solve these problems. In addition, a new structure is proposed to reduce the amount of computation, in which the adaptive control signal generator is realized by the paralel block structure. Simulation results are given to illustrate the performance of the proposed algorithm.

A new electron-beam wafer inspection system has been developed. The system has a resolution of 5 nm or better, and is applicable to quarter-micron devices such as 256 Mbit DRAMs. The most remarkable feature of this system is that a specimen stage is built in the objective lens and allows a working distance (WD) of 0. "WD=0"minimizes the effect of lens aberrations, and maximizes the resolving power. Innovative designs to achieve WD=0 are as follows: (1)A large objective lens of 730-mm width 730-mm depth 620-mm height that serves as a specimen chamber, has been developed. (2)A hollow specimen stage made of non-magnetic materials has been developed.It allows the lower pole piece and magnetic coile of the objective lens inside it. (3)Acoustic motors made of non-magnetic materials are em-ployed for use in vacuum.

In this study, an extraction method of failure sound signal which is strongly contaminated by noise is investigated by genetic algorithm and statistical tests of the frequency domain for the failure diagnosis of machinery. In order to check the extraction accuracy of the failure signal and obtain the optimum extraction of failure signal, the "existing probability Ps (t*k) of failure signal" and statistical information Iqp are defined as the standard indices for evaluation of the extraction results. It has been proven by practical field data and application of the inspection and diagnosis robot that the extraction method discussed in this paper is effective for detection of a failure and distinction of it's origin in the diagnosis of machinery.

Computer circumstance have changed drastically, and larger capacity removable media is indispensable. Magneto-optical disk is promising candidate to satisfy computer user's needs. In this report, future perspective of high density magneto-optical recording technology is investigated.

High power interference rejection characteristics of a sidelobe canceller which have not been well discussed yet are investigated through computer simulation and experiment in the real radio wave environment. To improve the high power interference rejection performance, a new method is considered. The performance of the method is also analyzed through computer simulation and experiment.

This paper discusses a coding-based selection approach to a communication aid for the severely motor disabled. Several approaches including row-column scanning are briefly described, then we propose a new selection scheme based on the theory of adaptive coding. They are compared each other with respect to average switch activations in generating some text samples.

Single-reference and multi-reference noise canceller (SRNC and MRNC) performances are investigated based on correlation between signal and noise. Exact relations between these noise canceller performances and signal-noise correlation have not been well discussed yet. In this paper, the above relations are investigated based on theoretical, analysis and computer simulation. The normalized LMS (NLMS) algorithm is employed. Uncorrelate, partially correlated, and correlated signal and noise combinations are taken into account. Computer simulation is carried out, using real speech, white noise, real noise sound, sine wave signals, and their combinations. In the SRNC problem, spectral analysis is applied to derive the canceller output power spectrum. From the simulation results, it is proven that the SRNC performance is inversely proportional to the signal-noise correlation as expected by the theoretical analysis. From the simulation results, the MRNC performance is more sensitive to the signal-noise correlation than that of SRNC. When the signal-noise correlation is high, by using a larger number of adaptive filter taps, the noise is reduced more, and, the signal distortion is increased. This means the signal components included in the noise are canceled exactly.

This paper deals with a high-speed digital circuit for discrete cosine transform (DCT). We propose a new algorithm that reduces the number of calculations for partial sum-of-products in the DCT and synthesize the small gate depth circuit of DCT by using carry-propagation-free adders based on redundant binary {1,0,1} representation. The gate depth is only half to one third that of the conventional algorithms with the same number of gates.

A new variable step size Least Mean Square (LMS) FIR adaptive filter algorithm (VSS-CC) is proposed. In the VSS-CC algorithm the step size adjustment (α) is controlled by using the correlation between the output error (e(n)) and the adaptive filter output ((n)). At small times, e(n) and (n) are correlated which will cause a large α providing faster tracking. When the algorithm converges, the correlation will result in a small size α to yield smaller misadjustments. Computer simulations show that the proposed VSS-CC algori thm achieves a better Echo Return Loss Enhancemen (ERLE) than a conventional NLMS Algorithm. The VSS-CC algorithm was also compared with another variable step algorithm, achieving the VSS-CC a better ERLE when the additive noise is incremented.

In this paper performance of M-stage detection for DS/CDMA is considered in terms of near-far resistance. Asymptotic multiuser efficiency (AME) of M stage detection over fading multipath channel is calculated and it is shown that even in the fading case the detector is near-far resistant i.e., insensitive to the relative energies of the users. The idea is extended to cellular environment. The effect of power control imperfection is investigated. It is shown that capacity can be increased if near-far resistant technique is employed in conjunction with limited power control.

This paper proposes a modified normalized LMS algorithm based on a long-term average of the reference input signal power. The reference input signal power for normalization is estimated by using two leaky integrators with a short and a long time constants. Computer simulation results compare the performance of the proposed algorithm with some previosuly proposed adaptive-step algorithms. The proposed algorithm converges faster than the conventional adaptive-step algorithms. Almost 30dB of the ERLE (Echo Return Loss Enhancement), which is comparable to the conventional algorithms, is achieved in noisy environments.

This paper presents a new structure for noise and echo cancelers based on a combined fast abaptive algorithm. The main purpose of the new structure is to detect both the double-talk and the unknown path change. This goal is accomplished by using two adaptive filters. A main adaptive filter Fn, adjusted only in the non-double-talk period by the normalized LMS algorithm, is used for providing the canceler output. An auxiliary adaptive filter Ff, adjusted by the fast RLS algorithm, is used for detecting the double-talk and obtaining a near optimum tap-weight vector for Fn in the initialization period and whenever the unknown path has a sudden or fast change. The proposed structure is examined through computer simulation on a noise cancellation problem. Good cancellation performance and stable operation are obtained when signal is a speech corrupted by a white noise, a colored noise and another speech signal. Simulation results also show that the proposed structure is capable of distinguishing the near-end signal from the noise path change and quickly tracking this change.

A P-Fuzzy Switching Function is a meaningful class of fuzzy switching functions that is representable by a logic formula consisting of prime implicants. This paper aima at extracting knowledge represented as prime implicants from a given learning data. The main results are the necessary and sufficient conditions for the learning data to be representable with P-fuzzy switching functions, and to be determined by unique logic formula.

In the early stage of hyperthermia, a large number of engineering efforts have been done in the development or the improvement of the heating and temperature measuring techniques. However, they were not always satisfactory clinically. Thus, even in this moment, various engineering researches as well as the electromagnetic techniques for hyperthermia should be build up rapidly. This paper describes some of the highlights of developed or ongoing electromagnetic heating techniques in hyperthermia and identities a trend of emerging electromagnetic heating. Furthermore, the author emphasizes that few medical engineering efforts have been done in the boundary field between pure physics and clinics, and the proper way to develop the hyperthermia equipment is the best use of successes in the three essential regions: Physics, Biology and Clinics.

This is an attempt to examine the contact resistance of a composite material which is used for sliding contacts. The composite material used here is sintered by dispersing the solid lubricant WS2 into the metallic base alloy Cu-Sn. A method based on Greenwood's formula is applied to determine how the calculated values are related to the contact resistance values obtained in our experiments. As a result, the composite material mated with the carbon specimen is found nearly to corresponds to the values of those calculated by the extended Greenwood's formula, whereas its value mated with the tungsten specimen does not. In short, it is concluded that the composite material mated with the carbon specimen consists of multispots.