The quantization error of phase delay in an ultrasonic annular arrays imaging system is analyzed which impairs image resolution, and proper sampling rate is considered to reduce system complexity.

This paper describes a new criterion for speech recognition using an integrated confidence measure to minimize the word error rate (WER). The conventional criteria for WER minimization obtain the expected WER of a sentence hypothesis merely by comparing it with other hypotheses in an n-best list. The proposed criterion estimates the expected WER by using an integrated confidence measure with word posterior probabilities for a given acoustic input. The integrated confidence measure, which is implemented as a classifier based on maximum entropy (ME) modeling or support vector machines (SVMs), is used to acquire probabilities reflecting whether the word hypotheses are correct. The classifier is comprised of a variety of confidence measures and can deal with a temporal sequence of them to attain a more reliable confidence. Our proposed criterion for minimizing WER achieved a WER of 9.8% and a 3.9% reduction, relative to conventional n-best rescoring methods in transcribing Japanese broadcast news in various environments such as under noisy field and spontaneous speech conditions.

We present the 10-bit current driver LSI with 2-set current digital-to-analog converters (DACs) and output channel current sample and hold (S/H) circuits for large-size and high-resolution active matrix organic light emitting diode (AMOLED) display applications. This current driver LSI has 300 output channels and the output current ranges from 0 µA to 290 µA. The maximum output current level can be controlled by 2-bit control signals because the maximum output current level depends on display size and resolution. The chip was fabricated using 0.65µm BiCMOS process and characterized. The chip size is 16.8 mm3.6 mm. Experimental results show that the output current DNL is less than 0.4 LSB and that INL is less than 1.5 LSB. This is good enough to apply 15.5 inch WXGA (1280RGB768) AMOLED displays.

A novel structure of a resonator type guided-wave electro-optic intensity modulator is introduced that uses a higher-order harmonic resonant electrode of coupled microstrip lines combined with polarization-reversed structure. The light modulation cancellation caused by the light transit-time effect in the resonant electrode, which is longer than the wavelength of the standing wave, is compensated for to enhance modulation efficiency. The modulator for 26 GHz operation was designed and fabricated with a LiTaO3 substrate. The modulation electrode is 9.03 mm long for seventh order harmonic resonance by RF signal. The workability of the modulator was confirmed by experiments with 1.3 µm wavelength light.

It is well-known that, in DS-CDMA downlink signal transmission, frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion can replace rake combining to achieve much improved bit error rate (BER) performance in severe frequency-selective fading channel. However, in uplink signal transmission, as each user's signal goes through a different channel, a severe multi-user interference (MUI) is produced and the uplink BER performance severely degrades compared to the downlink. When a small spreading factor is used, the uplink BER performance further degrades due to inter-chip interference (ICI). In this paper, we propose a frequency-domain multi-stage soft interference cancellation scheme for the DS-CDMA uplink and the achievable BER performance is evaluated by computer simulation. The BER performance comparison of the proposed cancellation technique and the multi-user detection (MUD) is also presented.

We experimentally investigated terahertz photomixing operation at room temperature in an InGaP/InGaAs/ GaAs two-dimensional plasmon-resonant photomixer incorporating grating-bicoupled dual-gate structure. Photoelectrons drifting into a high-density plasmon cavity grating from an adjacent low-density one extensively excite the plasmon resonance, resulting in emission of terahertz radiation. A vertical cavity formed between the two-dimensional plasmon grating plane and an indium-tin-oxide mirror at the back surface gains the radiation. Self-oscillation initially at around 4.5 THz excited by a dc-photo carrier component was reinforced by the photomixed differential-frequency excitation at 4.0 and 5.0 THz. This indicates a possibility of injection-locked oscillation of the photomixer in the terahertz frequency band.

In this Letter, we propose a least mean square (LMS) with adaptive step-size (AS) algorithm for adaptive blind carrier frequency offset (CFO) estimation in the orthogonal frequency division multiplexing system. In conjunction with the closed-loop estimate structure, the proposed algorithm eliminates the inter-carrier interference caused by time varying CFO. To improve the convergence performance of the fixed step-size LMS estimator, the regular AS LMS algorithm offers faster convergence speed and more accuracy to the CFO estimate. Several computer simulation examples are presented for illustrating the effectiveness of the proposed algorithm.

The design aspects of the bulk InGaAsP semiconductor optical amplifier integrated Mach-Zehnder interferometer (SOA-MZI) optimized for 40 Gbps-NRZ all optical wavelength conversion are described. The dimensions of the SOA active waveguide have been optimized for fast gain recovery by maximizing the gain and adjusting the wavelength-converted NRZ waveforms. Submicron-width buried heterostructure (BH) SOA waveguides were fabricated successfully and showed little leakage current. The experimental wavelength-converted optical waveform agreed well to the numerical simulations, and mask-compliant 40 G-NRZ wavelength-converted waveform was obtained by the optimized SOA-MZI. 40 G-NRZ full C-band operation and polarization-insensitive operation of SOA-MZI were also achieved.

Autocloned photonic crystals have corrugated multilayer structure. By related process technology, we can easily fabricate an array of polarizers or waveplates. Patterned photonic crystals are versatile component of many optical systems. This paper focuses on their use in optical microscopy. The main topics are: 1. Use of polarization imaging in microscopy, 2. generation of radial/circular polarization by a polarizer having concentric corrugations, 3. a "longitudinal polarization slit" (a new component) and its function in confocal microscopy, and 4. a polarization converter for generating "z-polarized" light at the focal point. In every application above, autocloned photonic crystals play a central role.

Buffer insertion plays a great role in modern global interconnect optimization. But too many buffers exhaust routing resources, and result in the rise of the power dissipation. Unfortunately, simplified delay models used by most of the present buffer insertion algorithms may introduce redundant buffers due to the delay estimation errors, whereas accurate delay models expand the solution space significantly, resulting in unacceptable runtime. Moreover, the power dissipation problem becomes a dominant factor in the state-of-the-art IC design. Not only transistor but also interconnect should be taken into consideration in the power calculation, which makes us have to use an accurate power model to calculate the total power dissipation. In this paper, we present two stochastic optimization methods, simulated annealing and solution space smoothing, which use accurate delay and power models to construct buffered routing trees with considerations of buffer/wire sizing, routing obstacles and delay and power optimization. Experimental results show our methods can save much of the buffer area and the power dissipation with better solutions, and for the cases with pins ≤ 15, the runtime of solution space smoothing is tens of times faster.

To keep in step with the rapid progress of high quality imaging systems, the Digital Cinema Initiative (DCI) has been issuing digital cinema standards that cover all processes from production to distribution and display. Various evaluation measurements are used in the assessment of image quality, and, of these, the required number of quantization bits is one of the most important factors in realizing the very high quality images needed for cinema. While DCI defined 12 bits for the bit depth by applying Barten's model to just the luminance signal, actual cinema applications use color signals, so we can say that this value has an insufficient theoretical basis. This paper, first of all, investigates the required number of quantization bits by computer simulations in discrete 3-D space for the color images defined using CIE's XYZ signal. Next, the required number of quantization bits is formulated by applying Taylor's development in the continuous value region. As a result, we show that 13.04 bits, 11.38 bits, and 10.16 bits are necessary for intensity, density, and gamma-corrected signal quantization, respectively, for digital cinema applications. As these results coincide with those from calculations in the discrete value region, the proposed analysis method enables a drastic reduction in the computer simulation time needed for obtaining the required number of quantization bits for color signals.

The present paper introduces the construction of a class of sequence sets with zero-correlation zones called zero-correlation zone sequence sets. The proposed zero-correlation zone sequence set can be generated from an arbitrary perfect sequence, the length of which is longer than 4. The proposed sets of ternary sequences, which can be constructed from an arbitrary perfect sequence, can successfully provide CDMA communication without co-channel interference. In an ultrasonic synthetic aperture imaging system, the proposed sequence set can improve the signal-to-noise ratio of the acquired image.

This paper presents a design method for AND-OR-EXOR three-level networks, where a single two-input exclusive-OR (EXOR) gate is used. The network realizes an EXOR of two sum-of-products expressions (EX-SOPs). The problem is to minimize the total number of products in the two sum-of-products expressions (SOPs). We introduce the notion of µ-equivalence of logic functions to develop exact minimization algorithms for EX-SOPs with up to five variables. We minimized all the NP-representative functions for up to five variables and showed that five-variable functions require 9 or fewer products in minimum EX-SOPs. For n-variable functions, minimum EX-SOPs require at most 9·2n-5 (n ≤ 6) products. This upper bound is smaller than 2n-1, which is the upper bound for SOPs. We also found that, for five-variable functions, on the average, minimum EX-SOPs require about 40% fewer literals than minimum SOPs.

In this letter, a low complexity ML detection technique for V-BLAST systems is proposed. In this proposed scheme, V probable streams are detected according to the first detected sub-stream of DFE detector and most probable stream is selected by likelihood test, since the performance of V-BLAST system depends on the first sub-stream detection capability. It has been shown that the proposed technique can detect the transmitted data more accurately than conventional DFE decoding scheme, and has very lower complexity than ML detector.

In order to reconstruct 3-D Euclidean shape by the Tomasi-Kanade factorization, one needs to specify an affine camera model such as orthographic, weak perspective, and paraperspective. We present a new method that does not require any such specific models. We show that a minimal requirement for an affine camera to mimic perspective projection leads to a unique camera model, called symmetric affine camera, which has two free functions. We determine their values from input images by linear computation and demonstrate by experiments that an appropriate camera model is automatically selected.

The frame-level R-D optimization in H.264 is very important in video storage scenarios. Among all of the sub-optimal algorithms, a greedy iteration algorithm (GIA) can best lower the computational complexity of frame-level R-D optimization. In order to further lower the computational complexity, a ρ-domain frame-level R-D optimization algorithm is proposed in this letter. Different from GIA, every frame's rate and distortion can be estimated accurately without actual encoding in our proposed algorithm. Simulation results show that our proposed algorithm can lower the computational complexity greatly with negligible variation in peak signal-to-noise ratio (PSNR) compared with GIA.

In this paper, a weighted element-wise block adaptive frequency-domain equalization (WEB-FDE) is proposed for a single-carrier system with the cyclic-prefix. In the WEB-FDE, the one-tap equalizer corresponding to a frequency-bin first preserves input DFT elements (element-wise block). Its coefficient in each block is then calculated by minimizing a weighted squared norm of the a posteriori error. Simulation results in a time-varying typical urban (TU) channel show that the bit-error-rate (BER) performance of the WEB-FDE outperform that of the normalized least-mean-square (NLMS)-FDE and recursive-least-square (RLS)-FDE.

As the channel frequency selectivity becomes severer, the bit error rate (BER) performance of direct sequence spread spectrum (DSSS) signal transmission with rake combining degrades due to an increasing inter-path interference (IPI). Frequency-domain equalization (FDE) can replace rake combining with much improved BER performance in a severe frequency-selective fading channel. For FDE, accurate estimation of the channel transfer function is required. In this paper, we propose an iterative channel estimation that uses pilot chips which are time-multiplexed within each chip block for fast Fourier transform (FFT). The pilot acts as a cyclic-prefix of FFT block as well. The achievable BER performance is evaluated by computer simulation. It is shown that the proposed channel estimation has a very good tracking ability against fast fading.

We consider the capacitated multi-source multicast tree routing problem (CMMTR) in an undirected graph G=(V,E) with a vertex set V, an edge set E and an edge weight w(e) ≥ 0, e ∈ E. We are given a source set S ⊆ V with a weight g(e) ≥ 0, e ∈ S, a terminal set M ⊆ V-S with a demand function q : M → R+, and a real number κ > 0, where g(s) means the cost for opening a vertex s ∈ S as a source in a multicast tree. Then the CMMTR asks to find a subset S′⊆ S, a partition {Z1,Z2,...,Zl} of M, and a set of subtrees T1,T2,...,Tl of G such that, for each i, ∑t∈Ziq(t) ≤ κ and Ti spans Zi∪{s} for some s ∈ S′. The objective is to minimize the sum of the opening cost of S′and the constructing cost of {Ti}, i.e., ∑s∈S′g(s)+w(Ti), where w(Ti) denotes the sum of weights of all edges in Ti. In this paper, we propose a (2ρUFL+ρST)-approximation algorithm to the CMMTR, where ρUFL and ρST are any approximation ratios achievable for the uncapacitated facility location and the Steiner tree problems, respectively. When all terminals have unit demands, we give a ((3/2)ρUFL+(4/3)ρST)-approximation algorithm.

This paper presents two steganographic methods for JPEG2000 still images which approximately preserve histograms of discrete wavelet transform coefficients. Compared with a conventional JPEG2000 steganography, the two methods show better histogram preservation. The proposed methods are promising candidates for secure JPEG2000 steganography against histogram-based attack.