This paper proposes an adaptive algorithm for identifying unknown systems containing nonlinear amplitude characteristics. Usually, the nonlinearity is so small as to be negligible. However, in low cost systems, such as acoustic echo canceller using a small loudspeaker, the nonlinearity deteriorates the performance of the identification. Several methods preventing the deterioration, polynomial or Volterra series approximations, have been hence proposed and studied. However, the conventional methods require high processing cost. In this paper, we propose a method approximating the nonlinear characteristics with a piecewise linear curve and show using computer simulations that the performance can be extremely improved. The proposed method can also reduce the processing cost to only about twice that of the linear adaptive filter system.

This primary objective of this study is to demonstrate simulation and ground-based experiment for the attitude control of flexible spacecraft. A typical spacecraft structure consists of the rigid body and flexible appendages which are large flexible solar panels, parabolic antennas built from light materials in order to reduce their weight. Therefore the attitude control has a big problem because these appendages induce structural vibration under the excitation of external forces. A single-axis rotational simulator with a flexible arm is constructed with on-off air thrusters and reaction wheel as actuation. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The experiment of flexible spacecraft attitude control is performed using only the reaction wheel. Using the reaction wheel the performance of the fuzzy-PID controller is illustrated by simulation and experimental results for a single-axis rotational simulator.

In this paper, we propose a distance-based howling canceller with high speech quality. We have developed a distance-based howling canceller that uses only distance information by noticing the property that howling occurs according to the distance between a loudspeaker and a microphone. This method estimates the distance by transmitting a pilot signal from the loudspeaker to the microphone. Multiple frequency candidates for each howling are computed from the estimated distance and eliminated by cascading notch filters that have nulls at them. However degradation of speech quality occurs at the howling canceller output. The first cause is a shot noise occurrence at the beginning and end of the pilot signal transmission due to the discontinuous change of the amplitude. We thus develop a new pilot signal that is robust against ambient noises. We can then reduce the shot noise effect by taking the amplitude small. The second one is a speech degradation caused from overlapped stopbands of the notch filters. We thus derive a condition on the bandwidths so that stopbands do not overlap, and propose an adaptive bandwidth scheme which changes the bandwidth according to the distance.

An improved dual-band design method is presented for the 180coupler. It uses the non-uniform impedance ring structure for the arbitrary power division and a π-shaped branch for the dual-band operation The increased design freedom offered by the proposed structure helps to extend the useful dual-band operation range.

The research on Delay Tolerant Networks (DTN) has been activated aiming at a variety of potential applications toward ubiquitous society. The vehicular network is one of the promising areas for applying DTN. In this paper, the end-to-end delay characteristics for vehicular ad-hoc broadcast DTN is analyzed, where the dynamic vehicle mobility model is introduced. The analysis is applied to the two realistic road models, that is, one-way and two-way traffic models. The simulation study demonstrates validity of our analysis for use in generic vehicle networks.

This paper focuses on optical integration technology and its application in optical microsensors used in biomedical fields. The integration is based on the hybrid integration approach, achieving high performance, small size and weight, and lower cost. First, we describe the key technologies used in hybrid integration, namely passive alignment technology, low temperature bonding technology, and packaging technology for realizing advanced microsensors. Then, we describe an integrated laser Doppler flowmeter that can monitor blood flow in human skin.

A new acceleration scheme that decreases the number of required iterations in relaxation methodology is proposed. The proposed scheme uses dynamic error prediction of an improved approximation to the solution during an iterative computation. The proposed scheme's application to circuit simulations required an average of 67.3% fewer iterations compared to un-accelerated relaxation methods.

The purpose of this study is the real-time estimation of Doppler spectral moments for precipitation in the presence of ground clutter overlap. The proposed method is a frequency domain approach that uses a Gaussian model both to remove clutter spectrum and to estimate weather spectrum. The main advantage of this method is that it does not use processes like several fitting procedures and enables to estimate profiles of precipitation in a short processing time. Therefore this method is efficient for real-time radar observation with high range and time resolution. The performance of this method is evaluated based on simulation data and the observation data acquired by the Ku-band broad band radar (BBR) [1].

In this letter, we first investigate the bias of Doppler shift estimator based on autocorrelation function (ACF). Then we derive a signal-to-noise ratio (SNR) independent condition for Doppler shift estimation and achieve this condition by a adaptive process. Moreover, we present theoretical analysis about the convergency of our adaptive Doppler shift estimator, and derive a close-form expression for its mean square error (MSE). We verify the proposed estimator by computer simulation, the results of which are in agreement with the analysis, i.e., the proposed method achieves a good SNR-independent performance in a wide range of velocities and SNRs.

This paper proposes an efficient design algorithm for power/ground (P/G) network synthesis with dynamic signal consideration, which is mainly caused by Ldi/dt noise and Cdv/dt decoupling capacitance (DECAP) current in the distribution network. To deal with the nonlinear global optimization under synthesis constraints directly, the genetic algorithm (GA) is introduced. The proposed GA-based synthesis method can avoid the linear transformation loss and the restraint condition complexity in current SLP, SQP, ICG, and random-walk methods. In the proposed Hybrid Grid Synthesis algorithm, the dynamic signal is simulated in the gene disturbance process, and Trapezoidal Modified Euler (TME) method is introduced to realize the precise dynamic time step process. We also use a hybrid-SLP method to reduce the genetic execute time and increase the network synthesis efficiency. Experimental results on given power distribution network show the reduction on layout area and execution time compared with current P/G network synthesis methods.

A novel voltage level controller for low-power charge pump converters will be presented in this paper. The proposed voltage level controller would react according to the pumped voltage in the charge-transfer-switch (CTS) converter. For the CTS circuit, the pumping operation would be degraded by the charge sharing effect in the auxiliary switch path. In this study, a voltage shifter was used as the voltage level controller to overcome this serious problem without consuming too much chip area. The simulation results showed that the converter can accept a rated input of 1.5 V and generated an output up to 8 V based on the TSMC 0.35-µm CMOS technology. The layout consumed an area of 125*160 µm2. The highest output obtained in measuring the real chip was 5.5 V which is primarily due to the limitation that the transistor could tolerated. The largest load was estimated as high as 6 mW which is large enough for on-chip application.

Because of the fact that mobile communication channel changes by time, it is necessary to employ adaptive channel equalizers in order to combat the distorting effects of the channel. Least Mean Squares (LMS) algorithm is one of the most popular channel equalization algorithms and is preferred over other algorithms such as the Recursive Least Squares (RLS) and Maximum Likelihood Sequence Estimation (MLSE) when simplicity is the dominant decision factor. However, LMS algorithm suffers from poor performance and convergence speed within the training period specified by most of the standards. The aim of this study is to improve the convergence speed and performance of the LMS algorithm by adjusting the step size using fuzzy logic. The proposed method is compared with the Channel Matched Filter-Decision Feedback Equalizer (CMF-DFE) [1] which provides multi path propagation diversity by collecting the energy in the channel, Minimum Mean Square Error-Decision Feedback Equalizer (MMSE-DFE) [2] which is one of the most successful equalizers for the data packet transmission, normalized LMS-DFE (N-LMS-DFE) [3] , variable step size (VSS) LMS-DFE [4] , fuzzy LMS-DFE [5],[6] and RLS-DFE [7] . The obtained simulation results using HIPERLAN/1 standards have demonstrated that the proposed LMS-DFE algorithm based on fuzzy logic has considerably better performance than others.

The multi-log2N network architecture is attractive for constructing optical switches, and the related routing algorithms are critical for the operation and efficiency of such switches. Although several routing algorithms have been proposed for multi-log2N networks, a full performance comparison among them has not been published up to now. Thus, we rectify this omission by providing such a comparison in terms of blocking probability, time complexity, hardware cost and load balancing capability. Notice that the load balance is important for reducing the peak power requirement of a switch, so we also propose in this paper a new routing algorithm for optical multi-log2N networks to achieve a better load balance.

Recently, reconfigurable devices are widely used in the fields of small amount production and trial production. They are also expected to be utilized in such mission-critical fields as space development, because system update and pseudo-repair can be achieved remotely by reconfiguring. However, in the case of conventional reconfigurable devices, configuration memory upsets caused by radiation and alpha particles reconfigure the device unpredictably, resulting in fatal system failures. Therefore, a reconfigurable device with high fault-tolerance against configuration upsets is required. In this paper, we propose an architecture of a fault-tolerant reconfigurable device that autonomously repairs configuration upsets by itself without interrupting system operations. The device consists of a 2D array of "Autonomous-Repair Cells" each of which repairs its upsets autonomously. The architecture has a scalability in fault tolerance; a finer-grained Autonomous-Repair Cell provides higher fault-tolerance. To determine the architecture, we analyze four autonomous repair techniques of the cell experimentally. Then, two autonomous repair techniques, simple multiplexing (S.M.) and memory multiplexing (M.M.), are applied; the former to programmable logics and the latter to cell-to-cell routing resources. Through evaluation, we show that proposed device achieves more than 10 years average lifetime against configuration upsets even in a severe situation such as a satellite orbit.

For developing design environment of various Dynamically Reconfigurable Processor Arrays (DRPAs), the Graph with Configuration Information (GCI) is proposed to represent configurable resource in the target dynamically reconfigurable architecture. The functional unit, constant unit, register, and routing resource can be represented in the graph as well as the configuration information. The restriction in the hardware is also added in the graph by limiting the possible configuration at a node controlled by the other node. A prototype compiler called Black-Diamond with GCI is now available for three different DRPAs. It translates data-flow graph from C-like front-end description, applies placement and routing by using the GCI, and generates configuration data for each element of the DRPA. Evaluation results of simple applications show that Black-Diamond can generate reasonable designs for all three different architectures. Other target architectures can be easily treated by representing many aspects of architectural property into a GCI.

Recently, multi-car elevator (MCE) system has captured attention as an effective mean for the improvement of transportation capability in a high-rise building. The MCE has two or more cars in one shaft. In this paper, we propose an algorithm for group controllers of MCE system, and show the effectiveness of our algorithm through computer simulation.

In this paper, we propose a fault tolerant hybrid p2p-CDN video streaming arhitecture to overcome the problems caused by peer behavior in peer-to-peer (P2P) video streaming systems. Although there are several studies modeling and analytically investigating peer behaviors in P2P video streaming systems, they do not come up with a solution to guarantee the required Quality of the Services (QoS). Therefore, in this study a hybrid geographical location-time and interest based clustering algorithm is proposed to improve the success ratio and reduce the delivery time of required content. A Hybrid Fault Tolerant Video Streaming System (HFTS) over P2P networks conforming the required QoS and Fault Tolerance is also offered. The simulations indicate that the required QoS can be achieved in streaming video applications using the proposed hybrid approach.

A highly integrated frequency quadrupler MMIC that uses three-dimensional MMIC (3D-MMIC) technology is presented. It consists of four driver amplifiers, two doublers, and a 2-band elimination filter. These seven circuits are integrated in only a 2.36 mm2 area. The filter sufficiently suppresses spurious output components. The third and fifth harmonic components, which are the spurious components nearest to the desired component, are well suppressed. The desired/undesired ratio is about 40 dB. The driver amplifiers make the quadrupler output a constant power of the desired multiplied signal under low input power. The MMIC supplies +5 dBm of the fourth harmonic component in the input power range from -10 dBm to +5 dBm. The power dissipation of the MMIC is only 160 mW.

This letter presents an efficient adaptive beamformer to deal with the multipath environments created by signal source scatterings. To improve the performance possible with the fixed forgetting factor, the regular adaptive forgetting factor algorithm is derived and applied to the subarray recursive least squares (RLS) beamforming. Simulations confirm that the proposed scheme has better performance than not only the conventional RLS algorithm but also the subarray RLS and adaptive forgetting factor RLS algorithms.

A strip line broadside hybrid coupler which is tolerant to manufacturing errors in a multi-layered LTCC substrate has been developed. The tolerance to a displacement error and a thickness variation in the multi-layered LTCC substrate can be achieved by using the tandem arrangement of diagonally shifted coupled lines with adjacent ground walls. It has been demonstrated that the coupling deviation from designed characteristics in our proposed hybrid coupler is very small.