The performance of parallel combinatory spread spectrum (PC/SS) communication systems in the frequency-nonselective, slowly Rayleigh fading channel is studied. Performance is evaluated by symbol error rate using numerical computation. To overcome the performance degradation caused by fading, we also studied the effects of selection diversity and Reed-Solomon coding applied to the PC/SS system. As a result, a remarkable improvement in error rate performance is achieved with Reed-Solomon coding and diversity technique. The coding rate for the maximum coding gain is almost a half of that in the additive white gaussian noise channel.

In this paper, an ARMA order selection method is proposed with a fuzzy reasoning method. In order to identify the reference model with the ARMA model, we need to determine its ARMA order. A less or more ARMA order, other than a suitable order causes problems such as; lack of spectral information, increasing calculation cost, etc. Therefore, ARMA order selection is significant for a high accurate ARMA model identification. The proposed method attempts to select an ARMA order of a time-varying model with the following procedures: (1) Suppose the parameters of the reference model change slowly, by introducing recursive fuzzy reasoning method, the estimated order is selected. (2) By introducing a fuzzy c-mean clustering methed, the period of the time during which the reference model is changing is detected and the forgetting factor of the recursive fuzzy reasoning method is set. Further, membership functions used in our algorithm are original, which are realized by experiments. In this paper, experiments are documented in order to validate the performance of the proposed method.

The effect of intersymbol interference resulting from non-matched receiver filtering on the bit error rate (BER) performance of π/4-DQPSK systems recently adopted in the North American and Japanese digital cellular standards, is analyzed in Rayleigh fading. With a Gaussian or a Butterworth (of order N, 2N10) receiver filter, the BER performance is found to degrade by only a small fraction of a decibel from the performance with ideally matched receiver filters. A 4th-order Butterworth receiver filter leads to BER curves which almost coincide with those of the ideally matched filtering condition.

This paper presents an adaptive MLSE (Maximum Likelihood Sequence Estimator) suitable for TDMA cellular systems. The proposed MLSE has two special features such as handling wide dynamic range signals without analogue gain controls and fast channel tracking capability. In order to handle wide dynamic range signals without conventional AGCs (Automatic Gain Controller), the proposed MLSE uses envelope components of received signals obtained from a non-linear log-amplifier module which has wide log-linear gain characteristics. By using digital signal processing technique, the log-converted envelope components are normalized and converted to linear values which conventional adaptive MLSEs can handle. As a channel tracking algorithm of the channel estimator, the proposed MLSE adopts a QT-LMS (Quick-Tracking Least Mean Square) algorithm, which is obtained by modifying LMS algorithm to enable a faster tracking capability. The algorithm has a fast tracking capability with low complexity and is suitable for implementation in a fixed-point digital signal processor. The performances of the MLSE have been evaluated through experiments in TDMA cellular environments with π/4-shifted QPSK, 24.3k symbol/sec. It is shown that, under conditions of 65dB amplitude variations and 80Hz Doppler frequency, the MLSE successfully achieves less than 3% B.E.R., which is required for digital cellular systems.

Myoelectric (ME) signals during dynamic movement suffer from motion arifact noise caused by mechanical friction between electrodes and the skin. It is difficult to reject artifact noises using linear filters, because the frequency components of the artifact noise include those of ME signals. This paper describes a nonlinear method of eliminating artifacts. It consists of an inverse autoregressive (AR) filter, a nonlinear filter, and an AR filter. To deal with ME signals during dynamic movement, we introduce an adaptive procedure and fuzzy rules that improve the performance of the nonlinear filter for local features. The result is the best ever reported elimination performance. This fuzzy rule based adaptive nonlinear artifact elimination filter will be useful in measurement of ME signals during dynamic movement.

This paper presents a structure of adaptive equalizer equipped with a neural network and a Viterbi decoder, and evaluates its performance under a fading environment by means of computer simulation.

The optical waveguides containing phthalocyanine as an optically active material were fabricated and transmission properties were investigated experimentally and numerically. The positive refractive index change was observed in the glass waveguide with a vanadyl phthalocyanine thin film as a top layer. The thermal influence on refractive index change was estimated by surface plasmon measurements.

Wave digital filters are a class of digital filters. They are equivalent to commensurate transmission line circuits synthesized with uniform, lossless, and commensurated transmission lines. In order to extend their applications to physical wave phenomena including quantum electronics, it is necessary to consider a generalized distributed line whose velocity of energy flow has frequency characteristics. This paper discusses a generalized distributed circuit, and we obtain two types of lines, lossless and cut-off. In order to analyze these lines, we discuss signal flow graphs of steady state voltage and current. The reflection factors we obtain here are the same as that for an active power or a diagonal element of a scattering matrix, which is zero in conjugate matching. By using this reflection factor, we obtain band-pass filters synthesized with the cut-off lines. We also describe an analysis method for nonuniform line related to Riccati differential equation.

The performance of selection diversity combined with decision feedback equalizer for reception of TDMA carriers is investigated in this paper. The second generation digital land mobile communication systems standardized in the U.S., Japan, and Europe employ TDMA carriers at transmission bit rates up to several hundreds kbit/s. In order to provide higher quality of mobile communications services to the user with employing TDMA carriers, the systems would require both diversity and equalization techniques to combat attenuation of received signal power level due to Rayleigh fading and intersymbol interference resulting from time-variant multipath fading, respectively. This paper proposes a novel integration method of selection diversity and decision feedback equalization techniques which provides the better bit error rate performance than that for the conventional selection diversity method with decision feedback equalizer. The feature of proposed method is that selection diversity and decision feedback equalization techniques are integrated so as to interwork each other. We call the proposed method by the Decision Feedback Diversity with Decision Feedback Equalizer. The detailed algorithm of the proposed method is first presented, and then the system parameters for the method are evaluated based on the computer simulation results. Finally the computer simulation results for the performance of the proposed method are presented and compared to those for the conventional Selection Diversity with Decision Feedback Equalizer and the conventional Dual Diversity Combining and Equalization method under the typical mobile radio environments, in order to demonstrate the validity of the proposed method.

This paper proposes Coherent-HYBrid Direct-Sequence Fast-Frequency-Hopping (CHYB-DS-FFH) CDMA with Adaptive Interference Cancelling (AIC) for cellular mobile communications. The features of CHYB-DS-FFH are symbol-by-symbol frequency diversity and low chip-rate DS multiplexing both of which are based on a coherent FFH modulation and demodulation scheme. The combination of coherent FFH, space diversity, and AIC is very effective for reducing the performance degradation due to interference. Computer simulations demonstrate BER performance of a 2 hop 500-kHz-interval frequency hopping system using () a linear canceller or () a nonlinear canceller. Both systems employ the two branch space diversity reception of 10kb/s QPSK with FFH over a 1MHz system bandwidth. In quasi-static channels, the average BER performance is 10-2 with average Eb/N0 less than 8dB. In dynamic fading channels under full interference conditions, CHYB-DS-FFH with the linear adaptive interference canceller realizes a BER of 10-2 at the average Eb/N0 of 15dB with maximum Doppler frequency fD of 5Hz, whereas CHYB-DS-FFH with the non-linear adaptive interference canceller achieves the same BER at the average Eb/N0 of 15dB with fD, equal to 30Hz.

Recent developments and case studies regarding VLSI device chip failure analysis are reviewed. The key failure analysis techniques reviewed include EMMS (emission microscopy), OBIC (optical beam induced current), LCM (liquid crystal method), EBP (electron beam probing), and FIB (focused ion beam method). Further, future possibilities in failure analysis, and some promising new tools are introduced.

A new image-based diagnostic method is proposed for use with an E-beam tester. The method features a static fault imaging technique and a navigation map for fault tracing. Static Fault imaging with a dc E-beam enables the fast acquisition of images without any additional hardware. Then, guided by the navigation map derived from CAD data, marginal timing faults can be easily pinpointed. A statistical estimation of the average count of static fault images for various LSI circuits shows that the proposed method can diagnose marginal faults by observing less than thirty faulty images and that a faulty area can be localized with up to five times fewer observations than with the guided-probe method. The proposed method was applied to a 19k-gate CMOS-logic LSI circuit and a marginal timing fault was successfully located.

We describe 2.5Gb/s 4 channel WDM transmission over 1060km using 18 EDFAs. Gain bandwidth narrowing in concatenated EDFAs has been successfully suppressed using unsaturated EDFAs and a 1.53µm ASE rejection filter.

This paper proposes a fast convergence algorithm for adaptive FIR filters with sparse taps. Coefficient values and positions are simultaneously controlled. The proposed algorithm consists of two stages： flat-delay estimation and tapposition control with a constraint. The flat-delay estimation is carried out by estimating the significant dispersive region of the impulse response. The constrained tap-position control is achieved by imposing a limit on the new-tap-position search. Simulation results show that the proposed algorithm reduces the convergence speed by up to 85% over the conventional algorithms for a white signal input. For a colored signal, it also converges in 40% of the convergence time by the conventional algorithms. The proposed algorithm is applicable to adaptive FIR filters which are to model a path with long flat delay, such as echo cancelers for satellite-link communications.

In order to evaluate the effect of testing technologies such as electron beam (EB) testing and focused ion beam (FIB) reconstruction on the VLSI development cycle, the VLSI development period and cost are analyzed by using detailed fault models which make possible to take into consideration the effect of EB and FIB techniques. First, the specifications of fabricated VLSIs and the VLSI development cycle are modeled. Next the faults which can be diagnosed by such testing techniques are modeled. By using the parametric model of the VLSI development cycle, the development period and cost are analyzed. In the fault diagnosis stage, the use of an EB tester or the combinational use of an EB tester and an FIB equipment, instead of a traditional mechanical prober is considered. It is seen that the development period and cost are reduced by using EB and FIB diagnosis equipments by a factor of about 3. The effect of scan path method is also evaluated by making use of the same simulation method. Results show that the scan path design is effective for the reduction in both period and cost in the development cycle.

A method to improve the efficiency of dynamic fault imaging (DFI) by fully utilizing the CAD data in the CAD-linked electron beam test system is proposed. In the method, in order to shorten the long acquisition time of the stroboscopic voltage contrast images over the whole area of the chip during the entire test cycle, only the area and phase (time) required for fault tracing are selected by utilizing the CAD data. Furthermore, image processing techniques are combined with the method to improve the efficiency of the DFI. In particular, the signal averaging technique is used in order to improve the signal-to-noise ratio in the stroboscopic images where all voltage information data on the equipotential electrode recognized by the CAD layout data are averaged. This enables us to reduce the acquisition time of images. Moreover, the experimental system is set up so that the image processing can be performed in parallel with the acquisition of the stroboscopic images. The proposed method is applied to part of a 2k-transistor block of a nonpassivated CMOS LSI where a marginal fault is detected. The result shows that the method is an efficient approach to the fully automatic fault diagnosis in the CAD-linked electron beam test system. The proposed method could improve the efficiency of the conventional DFI by a factor of more than 1000.

The mechanism for data retention failure of EPROM has been investigated by the Optical Beam Induced Current(OBIC) technique. It was found that the data of failure cells were changed from '1' to '0' during read-mode by laser irradiation by OBIC. The data in good cells was not changed. This result suggests the effective barrier height between Si and SiO2 is being lowered. In addition, the cross section technique revealed that gate electrode and gate oxide were exposed due to lack of dielectric layers. This defect seemed to be the cause of the barrier height lowering. The OBIC technique not only gives the failure location but a detailed information of the failure mechanism. We found that OBIC technique is a very powerful tool for the analysis of EPROM failure mechanisms. The usefulness of the Emission Micro Scope (EMS) technique is also discussed.

The origin of and a method of enhancing the Optical Beam Induced Resistance Change (OBIRCH) signal for defect observation in VLSI metal interconnections is discussed based on a numerical analysis of three-dimensional thermal conduction and experimental results. The numerical analysis shows that the OBIRCH signal originates from a slight increase in the resistance of the metal line caused by laser beam heating and that its effect is influenced by the temperature of the metal layer. Both simulations and experimental results suggest that cooling the sample is preferable to detect the OBIRCH signal. The decrease in the total resistance of the metal line without any change in the amount of the resistance increase under laser illumination is found to be the main cause of the OBIRCH signal enhancement under low temperature measurement.

Following a discussion of various testing methods used in the electron beam (EB) test system, new waveform-based and image-based approaches in the CAD-linked electron beam (EB) test system are proposed. A waveform-based automatic tracing algorithm of the transistor-level performance faults is first discussed. Then, the method to improve the efficiency of an image-based method called dynamic fault imaging (DFI) by fully utilizing the CAD data is described. Third, the VLSI development cost is analyzed by using the fault models that make possible to take into consideration the effect of new testing technologies such as EB testing and focused ion beam (FIB) microfabrication. Finally, the future prospects are discussed.

Upper bounds on the bit error probability and repeat request probability, and lower bounds on the throughput are derived for a Hybrid-ARQ scheme that employs trellis-coded modulation on a fading dispersive channel. The receiver employs a modified Viterbi algorithm to perform joint maximum likelihood sequence estimation (MLSE) equalization and decoding. Retransmissions are generated by using the approach suggested by Yamamoto and Itoh. The analytical bounds are extended to trellis-coded modulation on fading dispersive channels with code combining. Comparison of the analytical bounds with simulation results shows that the analytical bounds are quite loose when diversity reception is not employed. However, no other analytical bounds exist in the literature for the trellis-coded Hybrid ARQ system studied in this paper. Therefore, the results presented in this paper can provide the basis for comparison with more sophisticated analytical bounds that may be derived in the future.