Browsing by Author "Cheng, CC"

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A self-calibrated speaker tracking system using both audio and video data
(2002)
Hu, J
;
Su, TM
;
Cheng, CC
;
Liu, WH
;
Wu, TI
In this paper, a self-calibrated speaker tracking system applied on both image tracking and sound source detection is proposed. The sound source estimated by microphone system is used to supply video tracking system. On the other hand, the direction of speaker detected by image tracking system is fed back to calibrate the phase distortion between microphones. Some experiments using actual devices are also done to test the performance of the proposed method. It is shown that significant improvement in source localization accuracy is possible when the camera and the microphone system are well calibrated.
An automatic pin identification method for a three-phase DC brushless motor
(2005-10-01)
Wang, SJ
;
Cheng, CC
;
Lin, SK
;
Ju, JJ
;
Huang, DR
The pin identification is to find the definition of each connecting pin of a three-phase brushless motor. The 11 pins of the motor can be distinguished into three groups by a simple resistance measurement method. An automatic method has two steps. In the first step, the motor is in an open-circuited mode; and the individual pins of the windings are identified by comparing back electromotive forces. A special integral is defined and used to match Hall signal pins with the Hall sensors. The polarity of each pair of the Hall signal pins is determined by the second step of a standstill method. The proposed method is illustrated and verified by an experiment.
An hardware efficient deblocking filter for H.264/AVC
(2005)
Cheng, CC
;
Chang, TS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents an efficient VLSI architecture for the deblocking filter in H.264/AVC standard. The computing flow is reordered for easy hardware implementation. The resulting design can achieve 100 MHz with only gate count of 9.16K when synthesized from verilog RTL design by using UMC 0.18 mu m CMOS technology. When clocked at 82.58MHz, our design can easily support real-time deblocking of 2Kx1K@30Hz video application, this high performance can meet high resolution real-time application requirement.
Application of VSC reliable design to spacecraft attitude tracking
(2005)
Liang, YW
;
Xu, SD
;
Chu, TC
;
Cheng, CC
;
Liaw, DC
This study investigates variable structure reliable control issues of nonlinear systems and its applications to spacecraft attitude tracking problems. The proposed passive reliable control laws must know in advance which group of actuators is allowed to fail. These reliable controllers need not the solution of Hamilton-Jacobi (HJ) equation or inequality that are essentials in optimal approaches such as LQR and Hoo reliable designs. As a matter of fact, this approach is able to relax the computational load in computing the solution of HJ equation. The proposed reliable designs are also applied to spacecraft attitude tracking problems to explain their effectiveness and benefits. Finally, simulation results and comparisons between LQR and Variable Structure Control (VSC) reliable designs are presented to illustrate the merits of the proposed scheme. Although the proposed design is a passive one, it may provide a guideline for active design when a Fault Detection and Diagnosis (FDD) scheme is available.
Brightness enhancement of ITO/GaN LEDs by self-aligned micro-net structures
(2005)
Chang, KM
;
Chu, JY
;
Cheng, CC
;
Chu, CF
;
電子工程學系及電子研究所
Arrays of square and hexagonal holes of various dimensions were patterned on indium-tin-oxide (ITO)/GaN light-emitting diodes (LEDs) using the self-aligned method to increase the light extraction area and shorten the optical paths. The hole region was etched to give the sidewall of the active layer a sloped profile, and it was passivated by SiOxNy films to extract more light. The self-aligned micro-net LED is at least 10% brighter than the conventional structure in the normal direction without loss of operating voltage or leakage current. The ratio of luminescence to total output power is increased by 25% at a current density of 100 A/cm(2). Moreover, varying the hole dimensions and the designed density increased the peak external quantum efficiency by 5% at a current of 3 mA. The greater axial luminescence and the higher external quantum efficiency make LEDs self-aligned micro-net structures quite useful in surface-mounting and low-power-consuming devices, such as cellular phones. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Effects of composition on low temperature sinterable Ba-Nd-Sm-Ti-O microwave dielectric materials
(2004)
Cheng, CC
;
Hsieh, TE
;
Lin, IN
;
材料科學與工程學系
;
Department of Materials Science and Engineering
This work investigated the effects of MgO and ZnO additives on the microwave properties of BRT114 = [(BaO.R2O3.4TiO(2)).0.06(2Bi(2)O(3).3TiO(2))] materials. Incorporation of small amount of ZnO (less than or equal to1 wt.%) markedly lowered the temperature coefficient of resonant frequency (tau(f)), to around tau(f) = 1 ppm/degreesC, slightly increased the density and dielectric constant (epsilon(r)) of the materials, but degraded the Q x f factor. Doping 2.5 mol% of MgO, in addition to ZnO, further improved the tau(f)-value for the BRT114 materials. The dielectric constant and the Q x f factor of the materials degrade pronouncedly when doped with too abundant ZnO. Microstructure and EDX analyses indicated that the main factor for degrading the microwave properties is the induction on formation of secondary phases. Moreover, sol gel and fused Ba-B-Si glass reacted with BRT114 in quite a different way. Fused glass wets BRT114 materials more easily than the sol-gel derived glass, resulting in composite materials with higher density and larger dielectric constant. Precalcining the glass-dielectrics mixture, greatly improved the wetting ability of the glass and markedly increased the microwave properties of the glass/dielectric composite, i.e. LTCC materials. (C) 2003 Elsevier Ltd. All rights reserved.
Effects of postdeposition annealing on the characteristics of HfOxNy dielectrics on germanium and silicon substrates
(2006)
Cheng, CC
;
Chien, CH
;
Chen, CW
;
Hsu, SL
;
Yang, CH
We have systematically investigated the impact that postdeposition annealing (PDA) has on the physical and electrical properties of HfOxNy thin films sputtered on Ge and Si substrates. These two substrates display contrasting metal-oxide-semiconductor characteristics that we attribute to the different compositions of their interface layers (ILs). We observed an increased GeO2 incorporation into the HfOxNy dielectric and severe volatilization of the IL on Ge after higher PDA processing. These undesired phenomena in the HfOxNy/Ge gate stacks may be responsible for their different electrical properties with respect to those of the HfOxNy/Si gate stacks, i.e., a further scaling of the capacitance-equivalent thickness, a significant presence of fixed positive charges and electron-trapping sites, and a degradation of dielectric reliability. In addition, the anomalous low-frequency-like behavior of the high-frequency capacitance-voltage curves in inversion for the Ge capacitors was predicted from theoretical calculations. (c) 2006 The Electrochemical Society.
Electrical properties of SiN/GaN MIS diodes formed by ECR-CVD
(2002-09-01)
Chang, KM
;
Cheng, CC
;
Lang, CC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Silicon nitride (SiN) film was deposited at 300 degreesC as the insulating layer of a GaN-based metal-insulator-semiconductor (MIS) diode by using electron cyclotron resonance chemical vapor deposition (ECR-CVD) with silane-to nitrogen (SiH4/N-2) flow ratio of 5/45. The deposited film had the refractive index of 1.9-2.0 and the relative dielectric constant of 6. Capacitance-voltage (C-V) characteristics were measured at I MHz and interface state densities were obtained by Terman's method. The negative fixed charge density of the SiN film was 1.1 x 10(11) cm(-2) and its breakdown field was greater than 5.7 MV/cm even at 350 degreesC. The value of the interface state density was less than 4 x 10(11) cm(-2) around the mid-gap and its minimum was 5 x 10(10) cm(-2) eV(-1) at 0.6 eV below the conduction band edge. From these results, the SiN film deposited by ECR-CVD is a promising gate dielectric for high temperature GaN-MISFET application. (C) 2002 Elsevier Science Ltd. All rights reserved.
Excess low-frequency noise in ultrathin oxide n-MOSFETs arising from valence-band electron tunneling
(2005-09-01)
Wu, JW
;
You, JW
;
Ma, HC
;
Cheng, CC
;
Hsu, CF
Low-frequency flicker noise in analog n-MOSFETs with 15-angstrom gate oxide is investigated. A new noise generation mechanism resulting from valence-band electron tunneling is proposed. In strong inversion conditions, valence-band electron tunneling from Si substrate to polysilicon gate takes place and results in the splitting of electron and hole quasi-Fermi-levels in the channel. The excess low-frequency noise is attributed to electron and hole recombination at interface traps between the two quasi-Fermi-levels. Random telegraph signals due to the capture of channel electrons and holes is characterized in a small area device to support our model.
Fast three step intra prediction algorithm for 4x4 blocks in H.264
(2005)
Cheng, CC
;
Chang, TS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a fast three step algorithm for H.264 4x4 intra prediction. Motivated by the highly correlation of RD cost between different prediction direction, in each step of the algorithm, the proposed algorithm efficiently explores the neighborhood direction around the minimum one and thus skips other unlikely ones. Thus, the proposed algorithm can complete 4x4 intra prediction by only examining 6 modes instead of 9 modes in the full search algorithm. The simulation result shows that the proposed algorithm can maintain the similar PSNR quality to the full search algorithm with only about 1% bit-rate increase.
Frequency domain microphone array calibration and beamforming for automatic speech recognition
(2005-09-01)
Hu, JS
;
Cheng, CC
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電控工程研究所
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Institute of Electrical and Control Engineering
This investigation proposed two array beamformers SPFDBB (Soft Penalty Frequency Domain Block Beamformer) and FDABB (Frequency Domain Adjustable Block Beamformer). Compared with the conventional beamformers, these frequency-domain methods can significantly reduce the computation power requirement in ASR (Automatic Speech Recognition) based applications. Like other reference signal based techniques, SPFDBB and FDABB minimize microphone's mismatch, desired signal cancellation caused by reflection effects and resolution due to the array's position. Additionally, these proposed methods are suitable for both near-field and far-field environments. Generally, the convolution relation between channel and speech source in time domain cannot be modeled accurately as a multiplication in the frequency domain with a finite window size, especially in ASR applications. SPFDBB and FDABB can approximate this multiplication by treating several frames as a block to achieve a better beamforming result. Moreover, FDABB adjusts the number of frames on-line to cope with the variation of characteristics in both speech and interference signals. A better performance was found to be achievable by combining these methods with an ASR mechanism.
Highly reliable GaN-based light-emitting diodes formed by p-In0.1Ga0.9N-ITO structure
(2004-08-01)
Chang, KM
;
Chu, JY
;
Cheng, CC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Indium-tin-oxide (ITO) is deposited as a transparent current spreading layer of GaN-based light-emitting diodes (LEDs). To reduce the interfacial Schottky barrier height, a thin p-In0.1Ga0.9N layer is grown as an intermediate between ITO And p-GaN. The contact resistivity around 2.6 x 10(-2) Omega . cm(2) results in a moderately high forward voltage LED of 3.43 V operated at 20 mA. However, the external quantum efficiency and power efficiency are enhanced by 46% and 36%, respectively, in comparison with the conventional Ni-Au contact LEDs. In the life test, the power degradation of the p-In0.1Ga0.9N-ITO contact samples also exhibits a lower value than that of the conventional ones.
Hot carrier degradation in LDMOS power transistors
(2004)
Cheng, CC
;
Wu, JW
;
Lee, CC
;
Shao, JH
;
Wang, T
The hot carrier performance of N-LDMOS and P-LDMOS transistors is evaluated. For N-LDMOS transistors, the drain current degradation is shown to be due to hot electron injection in the drift region field oxide (bird's beak edge). On the other hand, the hot carrier-damaged region of P-LDMOS transistors is within the channel region, and hot electron is also the source of degradation.
Impact of post-deposition-annealing on the electrical characteristics of HfOxNy gate dielectric on Ge substrate
(2005-06-01)
Cheng, CC
;
Chien, CH
;
Chen, CW
;
Hsu, SL
;
Yang, MY
We systematically investigated the effect of post-deposition-annealing (PDA) on the electrical characteristics of Ge MOS capacitors with hafnium-oxynitride gate dielectric. The higher PDA temperature and longer PDA time was found to obtain the lower equivalent oxide thickness (EOT) of HfOxNy/Ge gate stack, however, with a larger hysteresis width. A lower EOT of 19.5 angstrom with a low leakage current of 1.8 x 10(-5) A/cm(2) at V-G = -1V was achieved after 600 degrees C annealing for 5 min. The improved capacitor properties after the PDA may be closely related to the different compositions and thicknesses of the resultant interfacial layers.
Low frequency noise degradation in ultra-thin oxide (I5A) analog n-MOSFETs resulting from valence-band tunneling
(2005)
Wu, JW
;
You, JW
;
Ma, HC
;
Cheng, CC
;
Hsu, C
Abnormal increase of low frequency flicker noise in analog n-MOSFETs with gate oxide in valence band tunneling domain is investigated. In 15 angstrom oxide devices, valence-band electron tunneling from Si substrate to poly-gate occurs at a positive gate voltage and results in the splitting of electron and hole quasi Fermi-levels in the channel. The excess low frequency noise is attributed to electron and hole recombination at interface traps between the two quasi Fermilevels. The trap capture and emission times in valence band tunneling domain are extracted from random telegraph signal. The dependence of measured trap times on gate voltage is consistent with our proposed model.
Microwave dielectric properties of glass-ceramic composites for low temperature co-firable ceramics
(2003)
Cheng, CC
;
Hsieh, TE
;
Lin, IN
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Ba-B-Si glass was added to Ba-Nd-Sm-Bi-Ti-O (BRT114) microwave dielectric material for LTCC applications. Conventional one-step processing method for preparing glass-BRT114 composite materials yields low dielectric constant, since the glass was easy to react with BRT114 and forms a low dielectric constant phase, Ba3B6Si2O16. A large proportion of pores appeared. The nature of glass, whether it is sol-gel derived or fused, shows marked influence on the microstructure and microwave dielectric properties of the composites. A two-step process containing precoating the BRT114 powders with a thin layer of glass, followed by conventional samples preparation process, tremendously improved the densification behaviour of the material. The formation of pores and interactions between glass and BRT114 was greatly suppressed such that materials with high dielectric constant (epsilon(r) = 40) were achieved by sintering 9 wt.% glass-containing composite at 950 degreesC for 2.5 h. (C) 2003 Elsevier Ltd. All rights reserved.
Nonlinear control for missile terminal guidance
(2000-12-01)
Liaw, DC
;
Liang, YW
;
Cheng, CC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Variable Structure Control (VSC) technique is applied to the design of robust homing missile guidance laws. In the design procedure, the target's maneuver is assumed to be unpredictable and is considered as disturbances. Guidance laws are then proposed to achieve the interception performance for both cases of longitude-axis control being available and unavailable. The proposed guidance laws are continuous which alleviate chattering drawback by classic VSC design. Results are obtained and compared with those by realistic true proportional navigation design to illustrate the benefits of the proposed decision. [S0022-0434(00)00604-3].
Pocket implantation effect on drain current flicker noise in analog nMOSFET devices
(2004-08-01)
Wu, JW
;
Cheng, CC
;
Chiu, KL
;
Guo, JC
;
Lien, WY
The pocket implantation effect on drain current flicker noise in 0.13 mum CMOS process based high performance analog nMOSFETs is investigated. Our result shows that pocket implantation will significantly degrade device low-frequency noise primarily because of nonuniform threshold voltage distribution along the channel. An analytical flicker noise model to account for a pocket doping effect is proposed. In our model, the local threshold voltage and the width of the pocket implant region are extracted from the measured reverse short-channel effect, and the oxide trap density is extracted from a long-channel device. Good agreement between our model and the measurement result is obtained without other fitting parameters.
Poly(2-hydroxyethyl methacrylate) film as a drug delivery system for pilocarpine
(2001-07-01)
Hsiue, GH
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Guu, JA
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Cheng, CC
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應用化學系
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Department of Applied Chemistry
This work investigates pilocarpine trapped in a matrix diffusion-controlled drug delivery system using hydrophilic inserts of Poly(2-hydroxyethyl methacrylate) (pHEMA) to ensure an increased bioavailability of pilocarpine and prolong the length of time in which the medication remains in the eyes of the test subjects. The physical and chemical properties of pilocarpine were investigated to elucidate the mechanism of drug-polymer interaction and the effect on drug release behavior of controlled release polymeric devices. In vitro release studies indicated that pilocarpine continued to be released from the inserts for a 24 h period. The results of intraocular pressure tests performed on albino rabbits were consistent with the observed in vitro behavior. The pressure decrease was significant for a period longer than 48 h. It confirms that the inserts, as sustainable releasing devices, are promising carriers for ophthalmic drug delivery systems. (C) 2001 Elsevier Science Ltd. All rights reserved.
Processing of speech signals using a microphone array for intelligent robots
(2005-03-01)
Hu, I
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Cheng, CC
;
Liu, WH
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電控工程研究所
;
Institute of Electrical and Control Engineering
For intelligent robots to interact with people, an efficient human-robot communication interface is very important (e.g. voice command). However, recognizing voice command or speech represents only part of speech communication. The physics of speech signals includes other information, such as speaker direction. Secondly, a basic element of processing the speech signal is recognition at the acoustic level. However, the performance of recognition depends greatly on the reception. In a noisy environment, the success rate can be very poor. As a result, prior to speech recognition, it is important to process the speech signals to extract the needed content while rejecting others (such as background noise). This paper presents a speech purification system for robots to improve the signal-to-noise ratio of reception and an algorithm with a multidirection calibration beamformer.