The DAPDNA®-2 is the world's first general purpose dynamically reconfigurable processor for commercial usage. It is a dual-core processor consisting of a custom RISC core called the Digital Application Processor (DAP), and a two dimensional array of dynamically reconfigurable processing elements referred to as the Distributed Network Architecture (DNA). The DAP has a 32 bit instruction set architecture with an 8 KB instruction cache and 8 KB data cache that can be accessed in one clock cycle. It has an interrupt control function to detect data processing completion in the DNA-Matrix. The DNA-Matrix has different types of data processing elements such as ALU, delay, and memory elements to process fully parallel computations. The DNA-Matrix includes 32 independent 16 KB high speed SRAM elements (in total 512 KB). The DNA-Matrix, even with its parallel computational capability, can be synchronized and co-work at the same clock frequency as the DAP. The processor operates at a 166 MHz working frequency and fabricated with a 0.11 µm CMOS process. The DAPDNA-2 device can be connected directly with up to 16 units with linear scalability in processing performance, provided the bandwidth requirement is within the maximum communication speed between DNAs, which is 32 Gbps. The DAPDNA-2 performs at a level that is two orders of magnitude higher than conventional high performance processors.

This paper describes a real-time blind source separation (BSS) method for moving speech signals in a room. Our method employs frequency domain independent component analysis (ICA) using a blockwise batch algorithm in the first stage, and the separated signals are refined by postprocessing using crosstalk component estimation and non-stationary spectral subtraction in the second stage. The blockwise batch algorithm achieves better performance than an online algorithm when sources are fixed, and the postprocessing compensates for performance degradation caused by source movement. Experimental results using speech signals recorded in a real room show that the proposed method realizes robust real-time separation for moving sources. Our method is implemented on a standard PC and works in realtime.

This paper proposes a PCB plane model for generic circuit simulators (SPICE). The proposed model reflects two frequency-dependent losses, namely, skin and dielectric losses. Once power/ground plane pair is divided into arrays of unit-cells, each unit-cell is modeled using a transmission line and the loss model. The loss model is composed of a resistor for DC loss, series RL ladder circuit for skin loss and series RC ladder circuit for dielectric loss. To verify the validity of the proposed model, it is compared with SPICE ac analysis using frequency-dependent resistors. Also, we show that the estimation results using the proposed model have a good correlation with that of VNA measurement for the typical PCB stack-up structure of general desktop PCs. With the proposed model, not only ac analysis but also transient analysis can be easily done for circuits including various non-linear/linear devices since the model consists of passive elements only.

Transmission performance of a multi-input multi-output (MIMO) antenna system (i.e., antenna diversity, adaptive antenna array, and space division multiplexing) highly depends on the arrival angle distribution of propagation paths. In this letter, a multipath fading simulator based on distributed scattering model is presented. The impacts of the arrival angle distribution of propagation paths on the bit error rates (BER) performance are measured using an implemented fading simulator and compared with the theoretically predicted performance.

An efficient way to optimize the hardware consumption in a low-voltage ΔΣ modulator for D/A converters is described. The modulator employs a ROM selection scheme for multiplications and the new buffer-and-routing ROM structure to minimize the hardware consumption. Furthermore, a guideline of the power-delay-and-area product (PDAP) for compelling issues such as power dissipation, delay time, and chip area consumption in the modern digital-circuit design is proposed. After the validity of the concept has been proved in comparison with that of the conventional guideline of the power-delay product in several behavioral blocks, it was employed in the circuit design. Fabricated in a standard digital 0.35-µm CMOS technology, the modulator achieves a signal-to-noise ratio (SNR) of 96 dB with an oversampling ratio of 256 under the supply of 2.0 V.

By modelling the quantization error as additive white noise in the transform domain, Wiener filter is used to reduce quantization noise for DCT coded images in DCT domain. Instead of deriving the spectrum of the transform coefficient, a DPCM loop is used to whiten the quantized DCT coefficients. The DPCM loop predicts the mean for each coefficient. By subtracting the mean, the quantized DCT coefficient is converted into the sum of prediction error and quantization noise. After the DPCM loop, the prediction error can be assumed uncorrelated to make the design of the subsequent Wiener filter easy. The Wiener filter is applied to remove the quantization noise to restore the prediction error. The original coefficient is reconstructed by adding the DPCM predicted mean with the restored prediction error. To increase the prediction accuracy, the decimated DCT coefficients in each subband are interpolated from the overlapped blocks.

A new algorithm, termed reduced-order Root-MUSIC, for high resolution direction finding is proposed. It requires finding all the roots of a polynomial with an order equaling twice the number of propagating signals. Some Monte Carlo simulations are used to test the effectiveness of the proposed algorithm.

In this article, it is shown that Unified Complex Hadamard Transform (UCHT) can be derived from Walsh functions and through direct matrix operation. Unique properties of UCHT are analyzed. Recursive relations through Kronecker product can be applied to the basic matrices to obtain higher dimensions. These relations are the basis for the flow diagram of a constant-geometry iterative VLSI hardware architecture. New Normalized Complex Hadamard Transform (NCHT) matrices are introduced which are another class of complex Hadamard matrices. Relations of UCHT and NCHT with other discrete transforms are discussed.

For a LEO constellation system, it is important to optimize the orbit parameters to maximize the quality of communication service. At the Next-generation LEO System (NeLS) Research Center, the LEO parameters were evaluated for a mobile satellite communication system. A 2π constellation was selected to maintain a stable inter-satellite link (ISL). An elevation angle above 20 degrees was required for a service area of 70 degree of latitude. The performance of optical ISL terminals has since improved as a result of key technological developments at the NeLS Research Center. As a consequence, the constellation parameters for ISL have become more flexible. Furthermore, the ability of ground station to access two satellites has improved communication quality. In this paper, we address the optimum constellation parameters for dual-satellite coverage. An equation for determining the optimum inclination angle was derived from the constellation parameters. Moreover, by using the new constellation parameters, we found that the satellite network consists of a bi-directional Manhattan Street Network (MSN), and the ISL network structure was improved.

This paper proposes an alternative learning algorithm for a stereophonic acoustic echo canceller without pre-processing which can identify the correct echo-paths. By dividing the filter coefficients into the former/latter parts and updating them alternatively, conditions both for unique solution and for perfect echo cancellation are satisfied. The learning for each part is switched from one part to the other when that part converges. Convergence analysis clarifies the condition for correct echo-path identification. For fast and stable convergence, a convergence detection and an adaptive step-size are introduced. The modification amount of the filter coefficients determines the convergence state and the step-size. Computer simulations show 10 dB smaller filter coefficient error than those of the conventional algorithms without pre-processing.

Motion estimation is the key issue in video compressing. Several methods for motion estimation based on the center biased strategy and minimum mean square error trend searching have been proposed, such as TSS, FSS, UCBDS and MIBAS, but these methods yield poor estimates or find local minima. Many other methods predict the starting point for the estimation; such methods include PMEA, PSA and GPS: these can be fast but are inaccurate. This study addresses the causes of wrong estimates, local minima and incorrect predictions in the prior estimation methods. The Multiple Searching Trend (MST) is proposed to overcome the problems of ineffective searches and local minima, and the Adaptive Dilated Searching Field (ADSF) is described to prevent prediction from wrong location. Applying MST and ADSF to the listed estimating methods, such as UCBDS, a fast and accurate can be reached. For this this reason, the method is called CockTail Searching (CTS).

This paper deals with a design problem of an adaptive robust control system for linear systems with structured uncertainties. The control law consists of a state feedback with a fixed gain designed by using the nominal system, a state feedback with an adaptive gain tuned by a parameter adjustment law and a compensation input. We show the parameter adjustment law and that sufficient conditions for the existence of the compensation input are given in terms of linear matrix inequalities (LMIs). Finally, a numerical example is included.

In this paper, we propose a design method of filters by successive projection (SP) method using multiple extreme frequency points based on Fritz John's theorem. In conventional SP method, only one extreme frequency point at which the deviation from the given specification is maximized is used in the update of the filter coefficients. Therefore, enormous amount of iteration numbers are necessary for research the solution which satisfies the given specification. In the proposed method, the updating coefficient using multiple extreme frequency points is possible by Fritz John's theorem. As a result, the solution converges less iteration number than the conventional SP method.

This paper analyzes the timing of eyeblink during visual identification of katakana characters on a display, which were presented under the constraint of a restricted visual field (R.V.F.). Blinks frequently occurred when the subject slowly brought the R.V.F. near a feature point (e.g., terminal point, crossing point).

The purpose of this paper is to present a rapid prototyping flow for the development of a wireless LAN system. The proposed system flow that was used for the development of the prototype is based on the use of UML (Unified Modeling Language). The UML and its real-time extensions are used to help the development phases of the prototype, mainly in the specification, co-simulation and validation of the design. The target of the development that was carried out with the application of the UML-based methodology is the implementation of an access point for a HIPERLAN/2 wireless network. Apart from the presentation of the UML-based system design methodology the paper also presents the application of the methodology for the implementation of the system prototype, the detailed software development and the results of the development.

Decision-directed, pilot-symbol-aided channel estimation (PSACE) for coded orthogonal frequency division multiplexing (COFDM) systems has structurally unavoidable processing delay owing to the generation of new reference data. In a fast fading environment, the channel condition which varies during the delay induces channel estimation error. This paper proposes a method of reducing this estimation error. In this method, channel equalization is performed for the received signal twice. One is done as pre-equalization with the delayed estimates of channel frequency response in order to update them periodically. At the same moment, the other is done as post-equalization for the received signal that is delayed by the processing delay time, with the same estimates as the pre-equalization. By the proposed method, more accurate channel estimation can be realized without significant output delay. Computer simulations are performed by utilizing the IEEE 802.11a packet structure of 24 Mbit/s. The result shows that the proposed OFDM transmission scheme having the delay time of 20 µs offers 2.5 dB improvement in the required Eb/N0 at PER = 10-2 in the ESTI-BRAN model C Rayleigh fading channel with fd = 500 Hz.

In uplink multicarrier code division multiple access (MC-CDMA), the inter-code interference (ICI) caused by the independent and frequency-selective fading channel of each user and the inter-carrier interference caused by the asynchronous reception of each user's OFDM symbols result in multiple access interference (MAI). This paper evaluates the ICI in frequency-selective Rayleigh fading channels for uplink MC-CDMA. We derive theoretical expressions for the desired-to-undesired signal power ratio (DUR) as a quantitative representation of ICI, and validate them by comparison with computer simulations using a Walsh-Hadamard (WH) code. Based on the analytical results, we obtain the optimum spreading sequence that minimizes the ICI (in short, maximizes the multiplexing performance); this sequence appears to be orthogonal. Three equalization combining methods are examined; equal gain combining (EGC), orthogonality restoring combining (ORC), and maximum ratio combining (MRC).

Inside a connector an interface with low insertion force and contact resistance is required, utilizing low cost materials such as copper alloys surrounded by tin coating. Relating to the application, the operating parameters have a wide range of values of currents, forces and materials. In this paper, we present a new experimental method based on non-intrusive probing of the deflection of the spring terminal with a laser technique. The main feature is that the reflection of the Laser beam onto the spring allows the determination of the contact force of the lamella-spring inside the female part. The technique requires the following insertion parameters during the insertion stroke: contact deflection δ, which allows contact force Fc, insertion force Fi and contact resistance Rc. It was found that the insertion force has a maximum value which decreases to the stable value, and depends on the size and the material of the pin. However contact resistance decreases sharply when first inserting, and tends to stable values on completing the insertion process, which is less sensitive to the pin diameter. Furthermore the final value which is important for the connector characterization is related and discussed. Finally, discrepancies were observed between the experimental and calculated data with simple numerical models. More complex models are in progress, which should improve the convergence of the theoretical approach to experimental results and proceed to the optimization of the connector parameters.

The Camera sensor network is a new advent of technology in which each sensor node can capture video signal, process and communicate with other nodes. We have investigated a dense node configuration. The requested processing task in this network is arbitrary view generation among nodes view. To avoid unnecessary communication between nodes in this network and to speed up the processing time, we propose a distributed processing architecture where the number of nodes sharing image data are optimized. Therefore, each sensor node processes part of the interpolation algorithm with local communication between sensor nodes. Two processing methods are used based on the image size shared. These two methods are F-DP (Fully image shared Distributed Processing) and P-DP (Partially image shared Distributed Processing). In this research, the network processing time has been theoretically analyzed for one user. The theoretical results are compatible with the experimental results. In addition, the performance of proposed DP methods were compared with Centralized Processing (CP). As a result, the best processing method for optimum number of nodes can be chosen based on (i) communication delay of the network, (ii) whether the network has one or more channels for communication among nodes and (iii) the processing ability of nodes.

Simultaneous wavelength conversion utilizing four-wave mixing in optically-pumped GaN/AlN intersubband optical amplifiers has been investigated by means of a finite-difference time-domain (FDTD) model. The conversion efficiencies at a pump power of +7-+10 dBm were predicted to be -9-+6 dB depending on the frequency detuning (0.3-10.9 THz). The difference in efficiency among 18 channels of WDM signals with 100-GHz spacing was within about 3 dB.