The Direct Sampling Mixer (DSM) with a complex coefficient transfer function is demonstrated. The operation theory and the detail design methodology are discussed for the high order complex DSM, which can achieve large image rejection ratio by introducing the attenuation pole at the image frequency band. The proposed architecture was fabricated in a 65 nm CMOS process. The measured results agree well with the theoretical calculation, which proves the validity of the proposed architecture and the design methodology. By using the proposed design method, it will be possible for circuit designers to design the DSM with large image rejection ratio without repeated lengthy simulations.

With the consideration of real-time stream processing technology, it's important to develop high availability mechanism to guarantee stream-based application not interfered by faults caused by potential anomalies. In this paper, we present a novel online prediction technique for predicting some anomalies which may occur in the near future. Concretely, we first present a value prediction which combines the Hidden Markov Model and the Mixture of Expert Model to predict the values of feature metrics in the near future. Then we employ the Support Vector Machine to do anomaly identification, which is a procedure to identify the kind of anomaly that we are about to alarm. The purpose of our approach is to achieve a tradeoff between fault penalty and resource cost. The experiment results show that our approach is of high accuracy for common anomaly prediction and low runtime overhead.

We have proposed a novel call admission control (CAC) for maximizing total user satisfaction in a heterogeneous traffic network and showed the effectiveness of our CAC by using an optimal threshold from numerical analysis [1]. In our previous CAC, when a new broadband flow arrives and the total accommodated bandwidth is more than or equal to the threshold, the arriving new broadband flow is rejected. In actual networks, however, users may agree to wait for a certain period until the broadband flow, such as video, begins to play. In this paper, when total accommodated bandwidth is more than or equal to the threshold, arriving broadband flows wait instead of being rejected. As a result, we can greatly improve total user satisfaction.

We have developed a process for the fabrication of high-quality Nb/AlOx/Nb tunnel junctions with small area and high current densities for the heterodyne mixers at millimeter and submillimeter wavelengths. Their dc I-V curves are numerically studied, including the broadening of quasiparticle density of states resulting from the existence of an imaginary part of the gap energy of Nb. We have found both experimentally and numerically that the subgap current is strongly dependent on bias voltage at temperatures below 4.2 K unlike the prediction of the BCS tunneling theory. It is shown that calculated dc I-V curves taking into account the complex number of the gap energy agree well with those of Nb/AlOx/Nb junctions measured at temperatures from 0.4 to 4.2 K. We have successfully built receivers at millimeter and submillimeter wavelengths with the noise temperature as low as 4 times the quantum photon noise, employing those high-quality Nb/AlOx/Nb junctions. Those low-noise receivers are to be installed in the ALMA (Atacama Large Millimeter/Submillimeter Array) telescope and they are going into series production now.

Substrate noise coupling has been seriously concerned in the design of advanced analog and radio frequency (RF) integrated circuits (ICs). This paper reviews recent advancements in the modeling, analysis, and evaluation of substrate noise coupling at IC chip level. Noise generation from digital circuits and propagation to the area of analog circuits are clearly visualized both by full-chip simulation as well as by on-chip measurements, for silicon test vehicles. The impacts of substrate noise coupling are also in-depth discussed at device, circuit, as well as system levels. Overall understanding of substrate noise coupling will then provide the basics for highly reliable design of analog and RF ICs.

The Kobayashi potential in electromagnetic theory is reviewed. As an illustration we consider two problems, diffraction of plane wave by disk and rectangular plate of perfect conductor. Some numerical results are compared with approximated and experimental results when they are available to verify the validity of the present method. We think the present method can be used as reference solutions of the related problems.

The aim of this study is to improve the accuracy of flicker parameters estimation in old film sequences in which moving objects are present. Conventional methods tend to fail in flicker parameters estimation due to the effects of moving objects. Our proposed method firstly utilizes an adaptive Gaussian mixture model (GMM)-based method to detect the moving objects in the film sequences, and combines the detected results with the histogram-matched frames to generate reference frames for flicker parameters estimation. Then, on the basis of a linear flicker model, the proposed method uses an M-estimator with the reference frames to estimate the flicker parameters. Experimental results show that the proposed method can effectively improve the accuracy of flicker parameters estimation when the moving objects are present in the film sequences.

The statistical static timing analysis has been studied intensively in the last decade so as to deal with the process variability, and various techniques to represent distributions of timing information, such as a gate delay, a signal arrival time, and a slack, have been proposed. Among them, the Gaussian mixture model is distinguished from the others in that it can handle various correlations, non-Gaussian distributions, and slew distributions easily. However, the previous algorithm of computing the statistical maximum for Gaussian mixture models, which is one of key operations in the statistical static timing analysis, has a defect such that it produces a distribution similar to Gaussian in a certain case, although the correct distribution is far from Gaussian. In this paper, we propose a new algorithm for statistical maximum (minimum) operation for Gaussian mixture models. It takes the cumulative distribution function curve into consideration so as to compute accurate criticalities (probabilities of timing violation), which is important for detecting delay faults and circuit optimization with the use of statistical approaches. We also show some experimental results to evaluate the performance of the proposed method.

The color appearance model gives us the proper brightness information and optimized display conditions for various viewing surroundings. However on conditions of low-level illumination or low background reflectivity, the performance of brightness estimation is relatively poor. Therefore, through our psychophysical experiments, we investigated the state of visual luminance adaptation for comparing single adaptations and mixed adaptations under a complex viewing field, and we also investigated background adaptation degrees and exponential nonlinearity factors for mixed adaptation models. It provides more accurate brightness predictions according to different adapting luminance, which is decided from object and background luminance.

This paper presents a low-power FPGA based on mixed synchronous/asynchronous design. The proposed FPGA consists of several sections which consist of logic blocks, and each section can be used as either a synchronous circuit or an asynchronous circuit according to its workload. An asynchronous circuit is power-efficient for a low-workload section since it does not require the clock tree which always consumes the power. On the other hand, a synchronous circuit is power-efficient for a high-workload section because of its simple hardware. The major consideration is designing an area-efficient synchronous/asynchronous hybrid logic block. This is because the hardware amount of the asynchronous circuit is about double that of the synchronous circuit, and the typical implementation wastes half of the hardware in synchronous mode. To solve this problem, we propose a hybrid logic block that can be used as either a single asynchronous logic block or two synchronous logic blocks. The proposed FPGA is fabricated using a 65-nm CMOS process. When the workload of a section is below 22%, asynchronous mode is more power-efficient than synchronous mode. Otherwise synchronous mode is more power-efficient.

A novel divide-by-3 injection-locked frequency divider (ILFD) is proposed. The ILFD circuit is realized with a cross-coupled n-core MOS LC-tank oscillator embedded with a push-push signal generator and two injection MOSFETs for coupling the injection signal into the resonator. The ILFD uses the linear mixer to extend the locking range and has been implemented in a standard 0.18 µm CMOS process. The core power consumption of the ILFD core is 3.12 mW. The divider's free-running frequency is tunable from 4.26 GHz to 4.9 GHz by tuning the varactor's control bias, and at the incident power of 0 dBm the locking range of the ILFD used as a divide-by-3 divider is 1.5 GHz, from 12.5 GHz to 14.0 GHz.

We demonstrate an all-optical picosecond pulse duration-tunable nonreturn-to-zero (NRZ)-to-return-to-zero (RZ) data format conversion using a Raman amplifier-based compressor and a fiber-based four-wave mixing (FWM) switch. A NRZ data signal is injected into the fiber-based FWM switch (AND gate) with a compressed RZ clock by the Raman amplifier-based compressor, and convert to RZ data signal by the fiber-based FWM switch. The compressed RZ clock train acts as a pump signal in the fiber-based FWM switch to perform the NRZ-to-RZ data format conversion. By changing the Raman pump power of the Raman amplifier-based compressor, it is possible to tune the pulse duration of the converted RZ data signal from 15 ps to 2 ps. In all the tuning range, the receiver sensitivity at bit error rate (BER) of 10-9 for the converted RZ data signal was about 1.31.7 dB better than the receiver sensitivity of the input NRZ data signal. Moreover, the pulse pedestal of the converted RZ data signals is well suppressed owing to the FWM process in the fiber-based FWM switch.

This paper presents a well-structured modified Booth encoding (MBE) multiplier which is applied in the design of a reconfigurable multiply-accumulator (MAC) core. The multiplier adopts an improved Booth encoder and selector to achieve an extra-row-removal and uses a hybrid approach in the two's complementation circuit to reduce the area and improve the speed. The multiplier is used to form a 32-bit reconfigurable MAC core which can be flexibly configured to execute one 3232, two 1616 or four 88 signed multiply-accumulation. Experimentally, when implemented with a 130 nm CMOS single-Vt standard cell library, the multiplier achieved a 15.8% area saving and 11.7% power saving over the classical design, and the reconfigurable MAC achieved a 4.2% area and a 7.4% power saving over the MAC design published so far if implemented with a mixed-Vt standard cell library.

In this paper, we propose a robust state estimation method using a particle filter (PF) for a class of nonlinear systems which have stochastic parameter uncertainties. A robust PF was designed using prediction and correction structure. The proposed PF draws particles from a simple proposal density function and corrects the particles with particle-wise correction gains. We present a method to obtain an error variance of each particle and its upper bound, which is minimized to determine the correction gain. The proposed method is less restrictive on system nonlinearities and noise statistics; moreover, it can be applied regardless of system stability. The effectiveness of the proposed robust PF is illustrated via an example based on Chua's circuit.

A sub-harmonic RF transmitter architecture with simultaneous power combination and carrier-leakage cancellation is proposed. It employs an 8-phase ring-type voltage controlled oscillator (VCO), sub-harmonic mixers, driver amplifiers, and a balun. A signal power is combined with its 180° phase-shifted signal through the balun. Simultaneously carrier-leakage generating in sub-harmonic mixers is canceled by its phase difference. The proposed transmitter achieved 1 dBm 1-dB output compression point (P-1dB) under 1.8 V supply and -40 dBm carrier-leakage in 5 GHz band.

This paper presents a Multiple-Input Multiple-Output (MIMO) propagation model for independent and identically distributed (i.i.d.) channels in the mixture of none-Line-of-Sight (NLOS) and Line-of-Sight (LOS) environments. The derived model enables to evaluate the system statistical characteristics of Signal-to-Noise-Ratio (SNR) for MIMO transmission based on Maximal Ratio Combing (MRC). An application example applying the model in 22 configuration to ITS Inter-Vehicle Communication (IVC) system is introduced. We clarify the effectiveness of the proposed model by comparisons of both computer simulations and measurement results of a field experiment. We also use the model to show the better performance of SNR when applying MIMO to IVC system than SISO and SIMO.

Precise estimation of data distribution with a small number of sample patterns is an important and challenging problem in the field of statistical pattern recognition. In this paper, we propose a novel method for estimating multimodal data distribution based on the Gaussian mixture model. In the proposed method, multiple random vectors are generated after classifying the elements of the feature vector into subsets so that there is no correlation between any pair of subsets. The Gaussian mixture model for each subset is then constructed independently. As a result, the constructed model is represented as the product of the Gaussian mixture models of marginal distributions. To make the classification of the elements effective, a graph cut technique is used for rearranging the elements of the feature vectors to gather elements with a high correlation into the same subset. The proposed method is applied to a character recognition problem that requires high-dimensional feature vectors. Experiments with a public handwritten digit database show that the proposed method improves the accuracy of classification. In addition, the effect of classifying the elements of the feature vectors is shown by visualizing the distribution.

This paper discusses speaker verification (SV) using Gaussian mixture models (GMMs), where only utterances of enrolled speakers are required. Such an SV system can be realized using artificially generated cohorts instead of real cohorts from speaker databases. This paper presents a rational approach to set GMM parameters for artificial cohorts based on statistics of GMM parameters for real cohorts. Equal error rates for the proposed method are about 10% less than those for the previous method, where GMM parameters for artificial cohorts were set in an ad hoc manner.

In this paper, we have derived a novel integral representation for the ground wave propagation over land-to-sea mixed-paths by applying the Helmholtz-Kirchhoff integral theorem. By using the method of stationary phase applicable uniformly as the stationary phase point approaches the endpoint of the integral, we have derived the asymptotic solution for the scattered fields consisting of the first-order and the second-order diffraction terms. We show that the asymptotic solution thus derived agrees with the asymptotic solution derived by applying the aperture field method (AFM) and the method of stationary phase. We have confirmed the validity and the utility of the novel integral representation and its asymptotic solution by comparing with the widely used mixed-path theorem and the experimental measurement performed in Kanto area and Tokyo bay.

We propose, in this letter, a new type of image denoising filter using a data analysis technique. We deal with pixels as data and extract the most dominant cluster from pixels in the filtering window. We output the centroid of the extracted cluster. We demonstrate that this graph-spectral filter can effectively reduce a mixture of Gaussian and random impulsive noise.