Because of noise and reverberation, accuracy of speech recognition systems decreases when the distance between talker and microphone increases. In this paper a new method for microphone array processing is proposed in which parameters of array processing are adjusted in calibration phase based on phones used in language and maximum likelihood method. Optimum filter length first studied and then optimized filter parameters are stored and used during recognition phase. A new modified Viterbi algorithm using optimal phone-based filter parameters is introduced for recognition phase. The proposed algorithm is analytically formulated and improvement in recognition accuracy in various noise level and reverberation time is studied.
In this paper, we present a blind algorithm for joint estimation of symbol timing offset (STO) and carrier frequency offset (CFO) for orthogonal frequency division multiplexing (OFDM) systems with I/Q imbalance. The proposed algorithm exploits the cyclostationarity of OFDM signals and relies on second-order statistics only. Estimation performance of the algorithm is evaluated by simulation and the results obtained in some typical scenarios are provided to show its effectiveness.
The parallel Fermat number transform (FNT) architecture is usually implemented with the code conversion (CC) and the butterfly operation (BO) in the diminished-1 number system. However, both the CC and the BO require too much area and delay due to modulo 2n+1 carry-propagation addition. In this paper, we propose a novel parallel FNT architecture with the root of unity 2 which is mainly composed of carry-save code conversion (CSCC) and carry-save butterfly operation (CSBO).The CSCC and the CSBO remove the carry-propagation addition by exploiting the property of carry-save adders. Thus the proposed FNT architecture requires less area and delay than the previous one. Synthesis results using 0.13-µm CMOS standard cells library demonstrate the superiority of the resulting architecture against the previously reported solution.
Instability of SRAM memory cells derived from aggressive technology scaling has become one of the most significant issues. Although lowering the supply voltage for a memory cell (VDDM) improves a write margin, which increases the access time. In this paper, we propose a memory cell employing a Look-ahead Active Body-biasing (LAB) scheme for SOI-SRAM with the dynamic VDDM control. Simulation results have shown that the proposed SRAM cell shortens the access time by 54% in the write mode, while expanding read and write margins and reducing effects of variations in the threshold voltage on them.
Optical inverse multiplexing is a promising technology for high-rate data transmission and rapidly increased demand for capacity. To realize this technology, a key issue is the buffering to alleviate the delay among parallel routes. As described in this paper, delay time characteristics of optical inverse multiplexing using optical parallel routes in WDM mesh networks are evaluated quantitatively for rapid capacity demand, comparison with the case of whether the existing route is still used or not.
In this paper, ESD protection circuit with substrate-triggered technique using PNP bipolar transistor for quick discharge of the electrostatic energy is proposed. The proposed ESD protection circuit is verified by the transmission line pulse (TLP) system. The results show that the proposed ESD protection circuit has lower trigger voltage (5.98V) compared with that of conventional GGNMOS. And the proposed circuit has faster turn-on time (∼37ns) than that of the conventional substrate-triggered ESD protection circuit.
Optical connectors are used both indoors and outdoors. To confirm the durability of optical connectors employing PC connection in actual outdoor environments, since 1997 we have been performing a reliability test on an SC connector installed in a high temperature and high humidity location. We confirmed that SC connectors with optimized ferrule end dimensions, which are designed to provide physical contact connection with long-term reliability, have maintained good levels of optical performance in an actual outdoor environment for 10 years.
The portable radio terminal for business is usually hold in the vicinity of a human body, it is needed an attention for the specific absorption rate (SAR) in an abdomen. Therefore, in order to evaluate the SAR in the human body when wearing the portable radio terminals for business, the normal-mode helical antenna (NHA) with metallic case, which simulates the portable radio terminals for business at 150MHz, was modeled. In addition, the calculations of SAR distributions employing an NHA with metallic case in the vicinity of the tissue-equivalent phantom were compared with the measurements. As a result, the SAR distributions of calculated result agree well with those of measured result.
This paper proposes a reversible data hiding method that embeds data into specific areas such as image edges. Though a reversible data hiding method distorts an original image to hide data, it not only extracts hidden data but also restores the original image from the distorted image. The proposed method memorizes only one parameter for data extraction and image restoration, and no location map recording watermarked positions is required. By simple modification to the conventional method that has the above mentioned features, the proposed method has a new function;hiding data to only specific areas.
In this paper, we propose a jointly designed diagonal precoder and minimum mean-square error receiver with ordered successive interference cancellation (MMSE-OSIC) for the double space-time transmit diversity (DSTTD) system with low feedback and low-complexity. The proposed transceiver utilizes the structure of the equivalent channel of DSTTD, showing lower computational complexity and better error rate performance than the conventional antenna shuffling schemes with the channel state information at the transmitter.
A long-range and high-resolution reflectometry by synthesis of optical coherence function at region beyond the coherence length is proposed. We discuss and simulate the principle of the reflectometry system. In basic experiments, the reflectivity distribution is successfully measured at the region beyond the coherence length with a spatial resolution of 19cm and a measurement range of 1km. We have also proposed two methods to improve dynamic range of the system. In the experiments, dynamic range of 45dB is successfully achieved.
A new tunable all-pass phase shifter architecture based on current mirror, with low complexity and power consumption is proposed in 0.18um CMOS, after a brief introduction on phase shifter applications. In the new current-mode approach the cut-off frequency of transistor is the operational limit of the proposed phase-shifter architecture and power consumption for this design is 80 microwatts. Simulations are carried out in HSpice and cover a frequency range from 1MHz to about 50GHz.
A new technique to reduce EMI in modular power multiconverters is described. The technique is based on a combination of switching frequency modulation and a variable delay between commutation signals of the single converters. The proposed technique has been validated experimentally in a four converters parallel topology. A significant EMI reduction has been obtained with regard to conventional techniques.
Defect inspection of thin film transistor liquid crystal displays (TFT-LCDs) is divided into two steps: detection and judgment. This letter proposes an automatic detection and judgment method for macro defects in the TFT-LCD color filter (CF) fabrication process using the diffraction pattern shift and chromaticity, respectively. The proposed method is verified via experiments using sampled CF glasses with macro defects, which were judged as PASS (no defect) in the CF fabrication process by a human operator who inspects CF glasses using conventional inspection systems, but were rejected in the module process. Seventeen rejected glasses were used in the experiments. All macro defects, including non-uniformity under 300Å, were detected and are judged as REJECT (defect) using the proposed method.
We propose a new type of optical fiber called homogeneous multi-core fiber (MCF) to drastically increase the transmission capacity of single fiber using the mode-division multiplexing. In this MCF, identical cores are closely arranged so that the cores are strongly coupled to each other to form coupled modes, each of which corresponds to a transmission channel. A novel mode multi/demultiplexer is proposed to discriminate each coupled mode. To rearrange cores to match the mode multi/demultiplexer, a hybrid configuration of coupled homogeneous with uncoupled heterogeneous multi-core is proposed. An example of hybrid configuration is designed so that the cross-talk becomes sufficiently small.