The most troublesome problem in automated X-ray mask inspection is how to exactly determine the threshold level for extracting the pattern portions of each scanning electron microscopic (SEM) image. An exact determination is difficult because the histogram shows, in most cases, a complicated multi-modal pattern and the true threshold level often varies with each successive image. This paper presents a novel thresholding approach for segmenting SEM images of X-ray masks. In this approach, the shape of the histogram of each image is iteratively analyzed until a threshold value minimizing the cost of the correspondence with a reference histogram and satisfying criteria for determining thresholds is obtained. This new approach is used in an automated inspection system. When the input image resolution is set to 0.05µm/pixel, experiments confirm 0.1µm defects are unfailingly detected.

This paper describes GaAs MMICs used in wireless LANs for spread spectrum communications on the ISM band. Both the transmitter and the receiver are incorporated inside the MMIC. In our experiment using prototypes at a center frequency of 2.45 GHz, the transmitter has a saturation output power of 21.4 dBm and the total current consumption is 131.2 mA. The receiver has a noise figure of3.2 dB and a gain of 12.2 dB.

Rate-based congestion control is a promising scheme as data transfer service in ATM networks, and has been standardized in the ATM Forum. To migrate the existing upper layer protocols to ATM networks, however, further investigation is necessary. In particular, when ABR service class is applied to TCP (Transmission Control Protocol), duality of congestion control schemes in different protocol layers, i.e., conventional window-based congestion control in the Transport layer and ratebased congestion control in the ATM layer, may have a unexpected influence on performance. As an alternative approach for supporting TCP protocol, EPD (Early Packet Discard) has been recently proposed, which adds the function to the UBR (Unspecified Bit Rate) service. It does not have a "duality problem" since EPD only discards cells selectively to improve packet-level performance. In this paper, we exhibit performance of TCP protocol over ATM networks by using a simulation technique. We first compare rate-based control of ABR service and EPD applied to UBR service, and show that rate-control achieves better fairness and higher throughput in most circumstances. However, rate-based control requires careful tuning of control parameters to obtain its effectiveness and a duality problem leads to unexpected degradation of TCP-level performance. By the rate-based congestion control, temporal congestion at the switch is quickly relieved by the rate down of the source terminals. However, our simulation explores that if the parameter set of the rate-based congestion control is not appropriately used, the congestion is also recognized at TCP due to packet drops and TCP unnecessarily throttles its window size. To avoid this sort of the problem, we develop the appropriate parameter set suitable to TCP on ABR service, and point out that some modification of TCP may be necessary for further performance improvement.

A new adaptive AR spectral estimation method is proposed. While conventional least-squares methods use a single windowing function to analyze the linear prediction error, the proposed method uses a different window for each frequency band of the linear prediction error to define a cost function to be meinemized. With this approach, since time and frequency resolutions can be traded off throughout the frequency spectrum, an improvement on the precision of the estimates is achieved. In this paper, a wavelet-like time-frequency resolution grid is used so that low-frequency components of the linear prediction error are analyzed through long windows and high-frequency components are analyzed through short ones. To solve the optimization problem for the new cost function, special properties of the correlation matrix are used to derive an RLS algorithm on the order of M2, where M is the number of parameters of the AR model. Computer simulations comparing the performance of conventional RLS and the proposed methods are shown. In particular, it can be observed that the wavelet-based spectral estimation method gives fine frequency resolution at low frequencies and sharp time resolution at high frequencies, while with conventional methods it is possible to obtain only one of these characteristics.

Asynchronous Transfer Mode (ATM) is a promised bearer transmission service for high speed multimedia LAN. Recently, high speed multimedia ATM LAN products have been available. Therefore, in order to interconnect them, the multimedia backbone LAN, which has the expandable high throughput over 10Gbps, supporting multicast, multi-QoS, and many interfaces including 622 Mbps, will be widely required. In this paper, the VLSI oriented input and output buffered switch architecture is proposed as the hardware architecture for multimedia backbone switch node. This paper describes that the chip set consisting of four VLSIs, that is, the switch element, the switch access, the distributor/arbiter, and the multiplexer/demultiplexer, can realize the backbone switch core, and the main specifications required to each VLSI are derived.

An adaptive decoding scheme for a concatenated code used in the frequency-hopped spread-spectrum communication system in the presence of a pulse-burst jammer is proposed and its performance is analyzed. Concatenated coding schemes employing binary inner-code and Reed-Solomon outer code are investigated and the use of side information is allowed to decode both erasures and errors. The proposed scheme makes the decoder enable to adapt to the jamming level by switching between two decoding modes such that the decoded bit error rate can be reduced. The optimal threshold value for switching in this proposed scheme is derived. It has been shown that the proposed decoding scheme yields a significant performance improvement over a conventional decoding scheme. In addition, performance analysis and its variation of adaptive decoding scheme with the imperfect side information are also presented.

Various kinds of new architectures have been proposed to enhance operating performance of the DRAM. This paper reviews these architectures including EDO, SDRAM, RDRAM, EDRAM, and CDRAM. The EDO slightly modifies the output control of the conventional DRAM architecture. Other innovative architectures try to enhance the performance by taking advantage of DRAM's internal multiple bits architecture with internal pipeline, parallel-serial conversion, or static buffers/on-chip cache. A quantitative analysis based on an assumption of wait cycles was made to compare PC system performance with some architectures. The calculation indicated the effectiveness of external or on-chip cache. Future trends cover high-speed I/O interface, unified memory architecture, and system integrated memory. The interface includes limited I/O swing such as HSTL and SSTL to realize more than 100MHz operation. Also, Ramlink and SyncLink are briefly reviewed as candidates for next generation interface. Unified memory architecture attempts to save total memory capacity by combining graphics and main memory. Advanced device technology enables system integration which combine system logic and memory. It suggests one potential direction towards system on a chip in the future.

This paper describes a new active pull-up (APU) interface for high-speed point-to-point transmission. The APU circuit is used to speed up a low-power-consumption open-drain-type interface. It pulls up the output at a fixed duration and this limiting of the pull-up duration prevents the pull-up operation from going into a counter phase at over 1-Gbps operation. Measurements of test chips fabricated with 0.25-µm bulk CMOS show. 1.7-Gbps error-free operation for the APU interface and 1.2-Gbps operation for the open-drain-type interface: The APU interface is 1.4 faster than the open-drain type. The application of a 0.25-µm SIMOX-CMOS device to the APU interface increases the bit rate 1.5 times compared with 0.25-µm bulk CMOS. Altogether the interface covers the bit rate of 2.4 Gbps, which is a layer of the communication hierarchy. The APU interface circuit can be applied to large-pin-count LSIs because of its full-CMOS single-rail structure.

A high speed and low power consumption SCFL circuit design with low supply voltage is proposed. Focusing on the relationship between logic swing and supply voltage, the lower limit for the supply voltage is presented. Theoretical analysis and circuit simulation indicates that the logic swing needs to be optimized to maintain high average gm within the swing. An SCFL D-FF fabricated using a 0.25 µm n-AlGaAs/i-InGaAs HJFET process operates at up to 10 Gbps with power consumption as low as 19 mW at a supply voltage of 1.3 V.

A directed graph G = (V,E) is called the n-rotator graph if V = {a1a2an|a1a2an is a permutation of 1,2,,n} and E = {(a1a2an,b1b2bn)| for some 2 i n, b1b2bn = a2aia1ai+1an}. We show that for any pair of distinct nodes in the n-rotator graph, we can construct n - 1 disjoint paths, each length < 2n, connecting the two nodes. We propose a nonadaptive fault-tolerant file transmission algorithm which uses these disjoint paths. Then the probabilistic analysis of its reliability is given.

It is demonstrated with the Berlekamp-Massey shift-register synthesis algorithm that the linear complexity value of binary complementary sequences is at least 3/4 of the sequence length. For some sequence pairs the linear complexity value can be even 0.98 times the sequence length. In the light of these results strongly non-linear complementary sequences are considered suitable for information security applications employing the spread-spectrum (SS) technique.

This paper clarified fundamental aspects of both triboelectric processes and electrostatic discharge (ESD) phenomena to the electronic systems. A chance for ESD can occur if a charged metal object (steel piped chair, for example) contacts or collides with another metal objects at moderate speed. At metal-metal ESD event, the metal objects act as a radiation antenna in a very short time (some 100ps, for example) which emanates impulsive electromagnetic fields with unipolarity into the surrounding space. Because of ESD at low-voltage (3kV or less) conditions, the direction of electrons movement at the spark gap is always unidirectional and fixed. The spark gap works as a momentary switch and also as a "diode." The dominant fields radiated from the metal objects are impulsive electric fields or impulsive magnetic fields which depend on the metal object's electrical and geometric conditions. This impulsive electromagnetic fields penetrate electronic systems, causing electromagnetic interference (EMI) such as malfunctions or circuit upset. The difference between EMI actions in high-voltage ESD and low-voltage ESD is experimentally analyzed in terms of energy conversion/consumption. A series of experiments revealed that EMI actions due to the metal-metal ESD are not proportional to the charge voltage nor the discharge current. In order to capture single shot impulsive electromagnetic fields very close to the ESD point (wave source), a short monopole antenna as an ultra broad-band field sensor was devised. As for signal transmissions between the short monopole antenna and the instrument (receiver), micro/millimeter wave techniques were applied. The transmission line's minimum band width DC-18.5GHz is required for time domain measurements of low-voltage ESD.

Arc discharge at switching contacts is one of the key phenomena, because it strongly affects material wear/transfer, contact resistance and electromagnetic interference (EMI). The arc discharge is classified into various types from the viewpoint of its sustaining mechanism and voltage waveform. They are mainly steady arc, showering arc and initial arc. Furthermore, a steady arc consists of two stages named metallic phase arc and gaseous phase arc. In the metallic, phase arc, metal ious from the electrodes mainly sustain the arc. On the other hand, gas ions from the surrounding atmosphere play an important role in the gaseous phase. Each phase arc has different influence on contact performance and EMI. The purpose of this paper is to review the arc discharges at light duty electrical contacts, and to survey the effects of arc discharges on material transfer and EMI.

This paper discusses the design of a small sensing device for EMI measurement which has equivalent characteristics to the absorbing clamp method, and reports the results on evaluation of the device. The device can be applied to the inspection apparatus for products such as power tools to examine conformance to EMI regulations of electromagnetic radiation spectrum. For reducing the scale of the EMI inspection apparatus, new matching circuit being replaced with the absorbing clamp method is adopted in the sensing device. Length of the sensing device is smaller than one twelfth of a wavelength of the measuring frequency in order to regard the sensing device as a concentrated constant circuit. The matching circuit is a resonant circuit which consists of a coaxial coupled transformer and a variable capacitor, and the transformer is a spiral copper tube in which a pair of AC power line wires passes. Resonant frequency of the circuit is tuned to the measuring frequency by adjusting the variable capacitor so that the circuit would terminate the power line by impedance zero. Thus interference current propagating along the power line from a product is absorbed, and observed by means of a VHF current probe which is settled in the matching circuit. A simple circuit for measurement of noise amplitude distribution (NAD) of interference current was developed as well as an equation to estimate quasi-peak value from the NAD. Result of measurement by the sensing device and proposed procedure confirmed good correlation with the standard absorbing clamp method, and deviation was within 3dB. Measurement time was reduced to 25 s per product, and the in-line EMI checker with new sensing device can be employed in a mass production line.

The local moment functions for discrete Wigner trispectrum are examined in ambiguity and in time-frequency domain. A concept of multiple and multidimensional circular convolution in frequency domain is introduced into the discrete Wigner higher order time-frequency signal representation of any order. It is shown that this concept based on the 1st order spectra of the signal offers an insight into the properties of inconsistent local moment functions and their representation both in ambiguity and time-frequency domain. It allows to prove that midfrequency crossterms of a multicomponent signal can not be removed by any generalized 4th order ambiguity function which employ kernel function in the ambiguity domain. It is shown, that the concept of multiple convolution in frequency domain can lead to the crossterm-reduced discete time-frequency representations of any order

Understanding unknown objects in images is one of the most important fields of the computer vision. We are confronted with the problem of dealing with the ambiguity of the image information about unknown objects in the scene. The purpose of this paper is to propose a new object recognition method based on the fuzzy relation system and the fuzzy integral. In order to deal with the ambiguity of the image information, we apply the fuzzy theory to object recognition subjects. Firstly, we define the degree of similarity based on the fuzzy relation system among input images and object models. In the next, to avoid the uncertainty of relations between the input image and the 2-D aspects of models, we integrate the degree of similarity obtained from several input images by the fuzzy integral. This proposing method makes it possible to recognize the unknown objects correctly under the ambiguity of the image information. And the validity of our method is confirmed by the experiments with six kinds of chairs.

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 letter presents an efficient design method of multiplierless 2-D state-space digital filters (SSDFs) based on a genetic algorithm. The resultant multiplierless 2-D SSDFs, whose coefficients are represented as the sum of two powers-of-two terms, are attractive for high-speed operation and simple implementation. The design problem of multiplierless 2-D SSDFs described by Roesser's local state-space model is formulated subject to the constraint that the resultant filters are stable. To ensure the stability for the resultant 2-D SSDFs, a stability test routine is embedded in th design procedure.

A unified process flow management system (UPFMS) that combines a CIM system, process/device simulator, CAD system, and manufacturing line schedular has been developed. This new system uses a new language called PDL to describe the process flow as common information for all systems. The UPFMS consists of the flow edit section, the flow inspection section, and several types of interface programs to make it suitable for use with other systems. The process flow data described using the PDL in the UPFMS provides data for controlling lots in CIM system. If modification of the process flow data in the CIM system is required, the process flow data is returned to the UPFMS and modified with inspection using a knowledge data base. Then, the error-free process flow data is sent back to the CIM system for Processes after flow inspection. Moreover, the UPFMS, with the new language PDL, generates recipe data for the equipment using an interface program, and recipe data is input to several types of equipment. Furthermore, the PDL process flow data can also be used as input data for the manufacturing line scheduler using another interface program. Mask and layout data in a CAD system can be exchanged among process/device simulators by using the UPFMS, and thus two-dimensional device characteristics. Spice paramenters can be also to be created. The UPFMS combines with CIM system, process/device simulator, CAD system, and the manufacturing line scheduler using common information, PDL. The process flow data created in the UPFMS can be used to control all systems from the simulation to CIM system as common data.

A microphone array system with multi-stage processing for speech enhancement is presented in this paper. Two beamformers with uniform directional patterns, one aimed at the target source and the other at the interfering sources, convert the multi-channel inputs into two data sequences. A novel microphone array structure with a small aperture has been designed to obtain the dual beamformers. The outputs of the two beam-formers are then presented to a post-processing stage to further improve the quality and intelligibility of the speech signal. The post-processing stage can be selected from one of three different algorithms that are presented, which are suitable for different acoustic environments. Applications for such a system include hands-free telephony, teleconferencing and also special situations where speech signals must be picked up in an extremely noisy acoustic environment in which the microphones are hidden (e.g. in a forensic covert recording system).