This paper describes how to generate, analyze and design a novel current-mode filter model using tunable multiple-output operational transconductance amplifiers and grounded capacitors (MO-OTA-Cs) for synthesizing both transmission poles and zeros. Transfer functions of low-order, high-order, general type, and special type are realized based on the filter model. The theory focuses mainly on establishing a relationship between the cascaded MO-OTA-Cs and the multiple-loop feedback matrix, which makes the structural generation and design formulas. Adopting the theory allows us to systematically generate many interesting new configurations along with some known structures. All the filter architectures contain only grounded capacitors, which can absorb parasitic capacitances and require smaller chip areas than floating ones. The paper also presents numerical design examples and simulation results to confirm the theoretical analysis.

A Rayleigh lidar (laser radar) system was developed and is now working well for temperature observations of the middle atmosphere at Poker Flat Research Range near Fairbanks, Alaska (65.1 N, 147.5 W). A comparison of lidar data and balloon sonde data showed good agreement in overlapped altitudes. The atmospheric fluctuations are detected in the temperature profiles obtained by the Rayleigh lidar and these are useful for the study of gravity waves. A Rayleigh Doppler lidar for wind measurements of the middle atmosphere is under the phase of development. The expected accuracy in measurements of horizontal winds up to an altitude of 60 km is smaller than 6 m/s in 2 hours observation. The system will be operated at Poker Flat after the completion of development. The combination of these lidars and radars installed at Poker Flat, give us chances of simultaneous observations of the structure and dynamics of the atmosphere in broad range of altitudes. Here, we give descriptions of the Rayleigh lidar and the Rayleigh Doppler lidar for the observations of the Arctic middle atmosphere at Poker Flat.

Magnetic layer thickness dependences of magnetic properties are investigated for Co-Cr-Pt polycrystalline thin films with different Cr-alloy underlayers (Cr-Ti, Cr-W, Cr-Mo, Cr-V, Cr-Mo-V). The specimens with Cr-Ti, Cr-V, and Cr-Mo-V underlayers show higher coercivities by about 30% and lower activation magnetic moments than those with Cr-Mo underlayer. The effective diameter of activation volume increases by 10-20% when the magnetic layer thickness is decreased from 12 to 8 nm. Temperature dependences of magnetic properties are also determined and discussed by referring to the data obtained using single crystal magnetic thin films with similar composition.

Aiming at lower cost and further miniaturization, we developed a new optical coupling system for use as an optical interface of a parallel optical interconnect module, called ParaBIT-1. It consists of a new-structure 24-fiber bare fiber (BF) connector whose main parts are made of molded plastic and a 24-channel optical coupling component using new polymeric optical waveguide film. To prevent bare fibers from breaking, the BF connector plug has a fiber protector. This BF connector can be joined by direct physical contact between bare fibers in fiber guide holes with a 250-µm pitch. The buckling forces of the fibers themselves secure the physical contacts. The average measured insertion loss of the 24-fiber BF connector was 0.05 dB, and the return losses were over 35 dB. The optical coupling components are composed of a 24-ch polymeric optical waveguide film with 45 mirrors and the 24-fiber BF connector interface, and can be assembled by passive alignment. The high thermal stability of the film allows soldering, and the film is fabricated by direct photo patterning. The average insertion losses of the components for transmitter and receiver modules were 1.28 and 1.35 dB, respectively.

A Frequency Modulated Continuous Wave (FMCW) radar using only in-phase channel is advantageous for automotive applications. In this radar, it is necessary to search the pairs of beat frequencies in an up-chirp mode and a down-chirp mode to measure the distances and the velocity of multiple targets similarly to a FMCW radar with both of in-phase and quadrature-phase channel. However the number of combinations to search the pairs is larger than that for the FMCW radar with both of in-phase and quadrature-phase channel. Therefore, false targets by mistaking the combination of these pairs increase. In this paper, we propose a novel measurement algorithm to reduce the false targets. We extract only the beat frequencies of the relatively moving targets using the differential frequency power spectrum of the up-chirp mode and the down-chirp mode. We can reduce the number of selected incorrect pairs by separating the stationary targets and the moving targets. We have conducted some simulations to confirm the capability of the proposed measurement algorithm. It was shown that the false target appearance probability is reduced without significant deterioration of the target detection probability.

The interconnect analysis of on- and off-chips is very important in the design of high-speed signal processing, digital communication, and microwave electronic systems. When the interconnects are characterized by sampled data via electromagnetic analysis, the circuit-level simulation of the network requires rational approximation of the sampled data. Since the frequency band of the sampled data is more than 10 GHz, the rational function must fit into it at many frequency points. The rational function is approximated using the orthogonal least-squares method. With an increase in the number of the fitting data, the least-squares method suffers from a singularity problem. To avoid this, the sampled data are hierarchically approximated in this paper. Moreover, to reduce the computational cost of the circuit-level simulation, the parameter matrix of the interconnects is approximated by a rational matrix with one common denominator polynomial, and the selective orthogonalization procedure is presented.

A surface extraction algorithm with NURBS has been developed for the mesh generation from the scattered data after a cell-based simulation. The triangulation of a surface is initiated with a step of describing the geometry along the polygonal boundary with multiple points. In this work, an NURBS surface can be generated with scattered data for each polygonal surface by employing a multilevel B-spline surface approximation. The NURBS mesh in accordance with our algorithm excellently represents the surface evolution of the topography on the wafer. A dynamically allocated topography model, so-called cell advancing model, is proposed to resolve an extensive memory requirement for the numerical simulation of a complicated structure on the wafer. A concave cylindrical DRAM cell capacitor was chosen to test the capability of our model. A set of capacitance present in the cell capacitor and interconnects was calculated with three-dimensional tetrahedral meshes generated from the NURBS surface on CRAY T3E supercomputer. A total of 5,475,600 (130 156 270) cells was employed for the simulation of semiconductor regions comprising four DRAM cell capacitors with a dimension of 1.3 µm 1.56 µm 2.7 µm . The size of the required memory is about 22 Mbytes and the simulation time is 64,082 seconds. The number of nodes for the FEM calculation was 70,078 with 395,064 tetrahedrons.

This paper proposes a new digital beamforming adaptive array antenna (DBFAAA) that is effective in severe multipath environments in which timing and carrier synchronization circuits cannot function ideally resulting in the DBFAAA losing control. The proposed DBFAAA has two stages. In the first, the DBFAAA captures the desired signal and establishes synchronization. In the second, the DBFAAA optimizes the beam pattern of the signal. The proposed configuration employs an eigenvector beam of the maximum eigenvalue in the first stage beam-forming. In addition, a fractionally-spaced-tapped-delay-line (FS-TDL) with real tap weights, which is placed after the beam-former, is applied to achieve timing synchronization. The behavior of the proposed DBFAAA for asynchronous sampling data is investigated and the results indicate that the proposed configuration enables asynchronous sampling at the A/D converter. A prototype of the proposed DBFAAA achieving 38-Mbps real-time data communication is introduced and the transmission performance is shown.

This paper analyses the performance of a joint receiving structure for DS-CDMA communications systems. To reduce undesirable performance degradation due to the multiple access interferences and the near-far problem in multipath fading channel environment, this paper exploits the receiving structure for the multiuser communication composed of a beamformer-RAKE receiver and a decorrelating multiuser detector. The proposed DS-CDMA receiving structure mitigates the performance impairment invoked from the noise enhancement and reveals less computational complexity by utilizing the multipath temporal combiner prior to accessing the decorrelating detection. Also an efficient block Toeplitz inversion technique using the matrix Levinson polynomials is introduced to further diminish the computational burden encountered from applying the decorrelating multiuser detection process as in usual. Simulation results are conducted to demonstrate the superior performance of the proposed multiuser detection structure in multipath fading CDMA channel.

In this paper the application of a linear-quadratic processor is proposed for detection of each user's signal in a direct sequence code division multiple access scheme and, in particular, for W-CDMA systems. In this method, the knowledge of the user of interest, and some statistical knowledge of interfering transmitters' signals are used to detect the desired user's signal without needing exact "a priori" knowledge of the interfering signal parameters such as spreading sequences and signal powers. Parameters of the proposed processor, which are derived so as to maximise the signal-to-interference-plus-noise ratio (SINR), can generally be obtained by solving a system of linear equations for which many effective techniques exist. A model for this detection procedure is developed and shown--through analytical and numerical results--to offer a good compromise between complexity and quality of performance.

The blind separation of sources is a recent and important problem in signal processing. Since 1984, it has been studied by many authors whilst many algorithms have been proposed. In this paper, the description of the problem, its assumptions, its currently applications and some algorithms and ideas are discussed.

An ultra low-noise and highly selective, experimental 2-GHz band cryogenic receiver front end (CRFE) has been newly developed for cellular base stations. It utilizes a high-Q superconducting filter, a very low noise cryogenic amplifier, and a highly reliable cooler that is very compact. Fundamental design of the CRFE is investigated. First, the equivalent noise temperature of the CRFE and the effect of improving CRFE sensitivity on base station reception are discussed. Next, essential technologies and fundamental characteristics of each component are described. Finally, influence of antenna noise, such as ground noise and man-made noise, is estimated through field tests both in urban and suburban areas.

To improve the resolution capability of the directions-of-arrival (DOA) estimation, some subspace-based methods have recently been developed by exploiting the specific signal properties (e.g. non-Gaussian property and cyclostationarity) of communication signals. However, these methods perform poorly as the ordinary subspace-based methods in multipath propagation situations, which are often encountered in mobile communication systems because of various reflections. In this paper, we investigate the direction estimation of coherent signals by jointly utilizing the merits of higher-order statistics and cyclostationarity to enhance the performance of DOA estimation and to effectively reject interference and noise. For estimating the DOA of narrow-band coherent signals impinging on a uniform linear array, a new higher-order cyclostationarity based approach is proposed by incorporating a subarray scheme into a linear prediction technique. This method can improve the resolution capability and alleviate the difficulty of choosing the optimal lag parameter. It is shown numerically that the proposed method is superior to the conventional ones.

Patterns exist in many contexts and can be considered the useful information for decision making. However, many patterns are not directly visible without careful presentation. Here, we describe an interactive visualization approach for browsing patterns in a history of interacting with a computer system. While a user is carrying out his/her business using computers, activities with respect to time and location are captured to determine the situational interactions. We first integrate the timeline and geographical map to create a structure to visualize spatiotemporal events in the interaction history. The spiral-based interactive visualization technique, presented in this paper, is then used to derive patterns according to the user-specified different spatial viewpoints on the map. In this study, we demonstrate how patterns can be used as visual statements for the analysis of a spatiotemporal data set in the information visualization.

This paper proposes a method for extracting subimages from a huge reference image by learning lifting wavelet filters. Lifting wavelet filters are biorthogonal wavelet filters containing free parameters developed by Sweldens. Our method is to learn such free parameters using some training subimages so as to vanish their high frequency components in the y- and x-directions. The learnt wavelet filters have the feature of training subimages. Applying such wavelet filters to the reference image, we can detect the locations where the high frequency components are almost the same as those of the target subimage.

Credit-based electronic payment systems are considered to play important roles in future automated payment systems. Like most other types of payment systems, however, credit-based systems proposed so far generally involve computationally expensive cryptographic operations. Such a relatively heavy computational load is preventing credit-based systems from being used in applications which require very fast processing. A typical example is admission-fee payment at the toll gate of an expressway without stopping a vehicle that travels at a high speed. In this article, we propose a very fast credit-based electronic payment protocol for admission-fee payment. More specifically, we propose a payment system between a high-speed vehicle and a toll gate which uses only very simple and fast computations. The proposed system makes use of an optimized Key Pre-distribution System (or KPS) to obtain high resistance against collusion attacks.

This paper proposes a moment based encoding algorithm for iterated function system (IFS) coding of non-homogeneous fractal images with unequal probabilities. Moment based encoding algorithms for IFS coding of non-homogeneous fractal images require a solution of simultaneous algebraic equations that are difficult to handle with numerical root-finding methods. The proposed algorithm employs a variable elimination method using Grobner bases with floating-point coefficients in order to derive a numerically solvable equation with a single unknown. The algorithm also employs a varying associated-probabilities method for the purpose of decreasing the computational complexity of calculating Grobner bases. Experimental results show that the average computation time for encoding a non-homogeneous fractal image of 256256 pixels and 256 gray levels is about 200 seconds on a PC with a 400 MHz AMD K6-III processor.

This paper newly proposes radio-over-fiber systems using cascaded radio-to-optic direct conversion (ROC) scheme. The ROC system can convert a radio signal into an optical signal with the same signal format. The received carrier-to-noise ratio (CNR) performance of the radio-over-fiber systems using the ROC/heterodyne detection (HD) scheme and the ROC/self-heterodyne detection (SHD) scheme are theoretically analyzed. The optimization of an optical modulation index (OMI) in each radio base station (RBS) is also presented. By using the proposed OMI optimization method, the ROC/HD and the ROC/SHD schemes are shown to provide approximately 16 dB and 14 dB improvement over the intensity modulation/direct detection scheme when the number of RBS is 20 and the radio-frequency (RF) signal bandwidth is 150 MHz, respectively. The ROC/SHD scheme enables a receiver structure to become simple while still achieving high received CNR.

This paper presents a pseudo glottal excitation model for the type of linear prediction vocoders with speech being coded at 1.6 kbps. While unvoiced speech and silence intervals are processed with a stochastic codebook of 512 entries, a glottal codebook with 32 entries for voiced excitation is used to describe the glottal phase characteristics. Steps of formulating the pseudo glottal excitation for one pitch period consist of 1) applying a polynomial model to simulate the low-frequency constituent of the residual, 2) inserting a magnitude-adjustable pulse sequence to characterize the main excitation, and 3) introducing turbulent noise in series with the resulting excitation. Procedures are described for codebook construction in addition to analysis and synthesis of the pseudo glottal excitation. Results in a mean opinion score (MOS) test show that the quality produced by the proposed coder is almost as good as that by 4.8 kbps CELP coder for male utterances, but the quality for female utterances is yet somewhat inferior.

This paper deals with the identification of system equation of the chaotic dynamics by using smaller number of data based upon the genetic programming (GP). The problem to estimate the system equation from the chaotic data is important to analyze the structure of dynamics in the fields such as the business and economics. Especially, for the prediction of chaotic dynamics, if the number of data is restricted, we can not use conventional numerical method such as the linear-reconstruction of attractors and the prediction by using the neural networks. In this paper we utilize an efficient method to identify the system equation by using the GP. In the GP, the performance (fitness) of each individual is defined as the inversion of the root mean square error of the spectrum obtained by the original and predicted time series to suppress the effect of the initial value of variables. Conventional GA (Genetic Algorithm) is combined to optimize the constants in equations and to select the primitives in the GP representation. By selecting a pair of individuals having higher fitness, the crossover operation is applied to generate new individuals. The crossover operation used here means the replacement of a part of tree in individual A by a part of tree in individual B. To avoid the meaningless genetic operation, the validity of prefix representation of the subtree to be embedded to the other tree is probed by using the stack count. These newly generated individuals replace old individuals with lower fitness. The mutation operation is also used to avoid the convergence to the local minimum. In the simulation study, the identification method is applied at first to the well known chaotic dynamics such as the Logistic map and the Henon map. Then, the method is applied to the identification of the chaotic data of various time series by using one dimensional and higher dimensional system. The result shows better prediction than conventional ones in cases where the number of data is small.