Browsing by Author "Wu, CC"

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A CMOS low-noise amplifier for ultra wideband wireless applications
(2005-11-01)
Chou, MF
;
Wuen, WS
;
Wu, CC
;
Wen, KA
;
Chang, CY
A CMOS low noise amplifier (LNA) for low-power ultrawideband (UWB) wireless applications is presented. To achieve low power consumption and wide operating bandwidth, the proposed LNA employing stagger tuning technique consists of two stacked common-source stages with different resonant frequencies. This work is implemented in 0.18-mu m CMOS process and shows a 2.4-9.4-GHz bandwidth. The amplifier provides a maximum forward gain (S-21) of 10.9 dB while drawing 7.1 mW from a 1.8-V supply. A noise figure as low as 4.1 dB and an IIP3 of -3.5 dBm have been demonstrated.
A loop partition technique for reducing cache bank conflict in multithreaded architecture
(1996-01-01)
Wu, CC
;
Chen, C
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
Parallel multithreaded architectures take advantage of the ability to execute more than one thread simultaneously on a single chip at low synchronisation and communication costs and high hardware resource utilisation. However, a high bandwidth cache, such as a multibank cache, is especially critical to serve memory accesses issued at the same time from different threads. To prevent bank conflicts of multibank cache from seriously degrading system performance, a loop partition method is proposed to reduce or even eliminate bank conflicts. The partition allows each thread access to certain bank modules and prevents any two from accessing the same bank module. The method neither slows down the clock rate nor increases the array subscript expression complexity. The performance gains of the bank-conflict-free loop partition approach are shown in simulation results.
A low power and high speed viterbi decoder chip for WLAN applications
(2003)
Lin, CC
;
Wu, CC
;
Lee, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a 166Mb/s, 64-state, radix-4, 16-level soft decison Viterbi decoder for high speed WLAN applications. With the path merging and trace forward techniques, the memory read operations are reduced to save power cunsumption. A test chip is fabricated in 0.35 mum 1P4M CMOS process, and can achieve the maximum throughout rate of 166Mbit/s under 3.3V The measured power consumption is below 55mW under 66M6/s throughput rate at 2.2V.
A low power CMOS low noise amplifier for ultra-wideband wireless applications
(2005)
Wu, CC
;
Chou, MF
;
Wuen, WS
;
Wen, KA
;
電子工程學系及電子研究所
A CMOS low noise amplifier (LNA) for low-power ultra-wideband (UNVB) wireless applications is presented. To achieve low power consumption and wide operating bandwidth, the proposed LNA employing stagger tuning technique consists of two stacked common-source stages with different resonance frequencies. This work is implemented in 0.18-mu m CMOS process and shows a 2.6-9.2-GRz bandwidth. The amplifier provides a maximum forward gain (S(21)) of 10.9 dB while drawing 7.1 mW from a 1.8-V supply. A noise figure as low as 3.5 dB and an IIP3 of -5.1 dBm have been demonstrated. In this paper, design optimization for the power-constrained stacked amplifiers in wide bandwidth applications is also presented.
A new relaxed memory consistency model for shared-memory multiprocessors with parallel-multithreaded processing elements
(1998-12-01)
Wu, CC
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
The release consistency model is the generally accepted hardware-centric relaxed memory consistency model because of its performance and implementation complexity. By extending the release consistency model, in this paper. we propose a hardware-centric memory consistency model particularly for shared-memory multiprocessor systems with parallel-multithreaded processing elements. The new model uses a new categorization for memory references and utilizes the feature of parallel multithreaded processors (PMPs). We further partition acquire and release references into three sub-categories: one for lock-unlock pairs, one for barrier synchronization, and the last for others. According to the semantic of each synchronization primitive, each sub-category has its own relaxed restrictions. On the other hand, the feature of a PMP is that it is capable of executing more than one thread at the same time, where all parallel threads share only one cache hierarchy. Under the new model, we can use dual write-caches to reduce write traffic and synchronization time. We have used five benchmarks in the SPLASH suite to evaluate the performance gain for the new model. According to the simulation results, the new model is superior to the release consistency model at best by about 11%.
A performance study of cache coherence protocols and write coaches for parallel-multithreaded shared-memory multiprocessors
(1998-01-01)
Wu, CC
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
According to published research results, no directory-based cache coherence protocol provides best performance for all application programs in conventional multiprocessor systems that use sequential consistency models. However, recently it has been claimed that competitive-update protocols are superior to other protocols under a relaxed consistency model. Moreover, incorporating write caches improves the system performance of clean and competitive-update protocols. In this paper, we examine the different effects that occur when processing elements are replaced by parallel-multithreaded processors. According to our simulation results, the clean protocol provided the best performance for five out of six SPLASH programs. After augmentation with write caches, the clean protocol outperformed others for all applications. Though competitive-update protocols have been improved, their performance is not better than that of write-invalidate protocols for most programs.
A performance study of cache coherence protocols and write coaches for parallel-multithreaded shared-memory multiprocessors
(1998-01-01)
Wu, CC
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
According to published research results, no directory-based cache coherence protocol provides best performance for all application programs in conventional multiprocessor systems that use sequential consistency models. However, recently it has been claimed that competitive-update protocols are superior to other protocols under a relaxed consistency model. Moreover, incorporating write caches improves the system performance of clean and competitive-update protocols. In this paper, we examine the different effects that occur when processing elements are replaced by parallel-multithreaded processors. According to our simulation results, the clean protocol provided the best performance for five out of six SPLASH programs. After augmentation with write caches, the clean protocol outperformed others for all applications. Though competitive-update protocols have been improved, their performance is not better than that of write-invalidate protocols for most programs.
Anomalous spin polarization and dualistic electronic nature of CrO(2)
(2003-06-01)
Huang, DJ
;
Tjeng, LH
;
Chen, J
;
Chang, CF
;
Wu, WP
Spin-resolved O 1s x-ray absorption measurements on CrO(2) reveal that the spin polarization of the states at the Fermi level approaches 100%, providing direct evidence of the half-metallic nature of CrO(2). The measurements also show the existence of an atomiclike Cr 3d state not far away from the Fermi level with a spin polarization of only 50%, establishing its Mott-Hubbard character. We conclude that CrO(2) has a dualistic electronic nature, in which the states at the Fermi level are bandlike, while those at higher energies are strongly localized of completely different origin and symmetry. The finding of an exceptionally large number of O 2p holes suggests their important role in preventing the strongly correlated CrO(2) from being an insulator.
Anomalous spin polarization and dualistic electronic nature of CrO2
(2003-06-01)
Huang, DJ
;
Tjeng, LH
;
Chen, J
;
Chang, CF
;
Wu, WP
Spin-resolved O 1s x-ray absorption measurements on CrO2 reveal that the spin polarization of the states at the Fermi level approaches 100%, providing direct evidence of the half-metallic nature of CrO2. The measurements also show the existence of an atomiclike Cr 3d state not far away from the Fermi level with a spin polarization of only 50%, establishing its Mott-Hubbard character. We conclude that CrO2 has a dualistic electronic nature, in which the states at the Fermi level are bandlike, while those at higher energies are strongly localized of completely different origin and symmetry. The finding of an exceptionally large number of O 2p holes suggests their important role in preventing the strongly correlated CrO2 from being an insulator.
Barrier capability of TaNx films deposited by different nitrogen flow rate against Cu diffusion in Cu/TaNx/n(+)-p junction diodes
(2001-01-01)
Yang, WL
;
Wu, WF
;
Liu, DG
;
Wu, CC
;
Ou, KL
This paper investigates the barrier capability of tantalum nitride (TaNx) layers against Cu diffusion. The TaNx layers were reactively sputtered in contact holes to a thickness of 50 nm by using a different nitrogen flow rate. Results indicate that the TaNx layers fail to be a diffusion barrier due to a relative high resistivity for nitrogen flow ratios exceeding 10%. in addition, we found that the phase of alpha -Ta(-N) functions as an effective barrier against Cu diffusion and that Cu/TaN(3-5%)/n(+)-p junction diodes are able to sustain a 30 min furnace anneal up to 500 degreesC without causing degradation of the electrical characteristics. The high-temperature failure of barrier capability for the TaNx layers is due to interdiffusion of Cu and Si across the TaNx film structure to form Cu3Si. The surface roughness and the film structure of TaNx layers determine the ability of Cu and Si interdiffusion. (C) 2001 Elsevier Science Ltd. All rights reserved.
Bound water content and water binding strength on sludge flocs
(1998-03-01)
Wu, CC
;
Huang, CP
;
Lee, DJ
;
環境工程研究所
;
Institute of Environmental Engineering
On the basis of the thermodynamic hypothesis and using the thermodynamic approach, a binding strength was calculated to define the physical meaning of bound water content of sludge as measured by dilatometer. The sludge samples considered in this study included kaolin, alum and biological sludge. The binding strength of bound water at -20 degrees C was calculated as 24.5 kJ/kg, which is close to that of the normal physico-adsorption process. Most of the frozen moisture in st dilatometric measurement should be interstitial water or vicinal water. Results also indicated that moisture with a lower binding strength easily became free water. The release of interstitial water from sludge flocs would cause less bound water. When solid concentration is higher, the expelling strength induced by the compacting action of sludge flocs is increased over the binding strength, thereby forcing out the interstitial water. Lower bound water contents are attained. Accurate measurement of bubble volumes with the calculated stem on the top of the dilatometer could improve the precision of expansion coefficient and bound water content measurement. (C) 1998 Elsevier Science Ltd. All rights reserved.
Design of a scalable multiprocessor architecture and its simulation
(2001-09-01)
Pean, DL
;
Wu, CC
;
Chua, HT
;
Chen, C
;
資訊工程學系
Performance enhancement and system scalability are two of the most important issues in the design of multiprocessor systems. A scalable cluster-based multiprocessor architecture and its simulation environment called SEECMA are proposed. Several new issues in our architecture, including scalable cache coherence protocols, relaxed memory consistency models, memory optimization techniques and several types of processors are considered. It has been developed to meet current trends in clustering architecture design. Additionally, the SEECMA environment is presented as a helpful investigation tool for both education and research. In addition to many simulation options. it is provided with a user-friendly graphic interface. SEECMA can automatically collect data from several simulation runs and display the results for comparison. So far. we have evaluated several vital issues of cluster-based multiprocessors on SEECMA including effective prefetching and replacement policies, and optimization of migratory sharing using both hardware and software mechanisms. On average, these enhance system performance by up to 8%, 9%, and 7%. respectively. Our cluster-based multiprocessor architecture also scales more readily than the current general, or cluster-based, multiprocessor environments. (C) 2001 Elsevier Science Inc. All rights reserved.
Determination of the optimal dose of polyelectrolyte sludge conditioner considering particle sedimentation effects
(2000-08-01)
Wu, CC
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
The specific resistance to filtration (SRF) of sludge was determined using both a leaf filter and a Buncher funnel. The filterability of a kaolin suspension and an alum sludge were characterized using SRF data and capillary suction time (CST) measurements. Filter orientation during the leaf filter test and stirring during the Buncher funnel test affected the SRF values, and the optimal dosage of polyelectrolyte conditioner (defined as the dosage that yields the minimum resistance to filtration) varied depending on the type of test used. Therefore, the optimal dose of polyelectrolyte was an operationally defined value that depended on the geometry of the filter chamber and fluid/particle interactions, such as sedimentation. (C) 2000 Elsevier Science Ltd. All rights reserved.
Dewatering characteristics of algae-containing alum sludge
(1999-05-01)
Pan, JR
;
Huang, CP
;
Chuang, YC
;
Wu, CC
;
環境工程研究所
The presence of algae in source waters not only causes problems in the water treatment process, but also complicates the treatment and disposal of sludge. This has become a major concern in Taiwan because of the increasing eutrophication of water sources. The purpose of this study was to determine the effects of algae during aging process on the characteristics of potable water treatment residuals and investigate their conditioning in order to provide water treatment plants with guidelines for treating algae-containing sludge. In this study, we measured the bound water content and CST to evaluate the influence of algae and their exudates on sludge conditioning. The change in zeta potential was monitored during sludge aging. During the aging process up to 5 days, the surface charge of sludge became more negative and the dewaterability was enhanced by algal exudates. Microphotographs of the algae-containing sludge suggest that algae and their exudates cause the bio-flocculation phenomenon. (C) 1999 Elsevier Science B.V. All rights reserved.
Effect of electron-phonon scattering mechanisms on free-carrier absorption in quasi-one-dimensional structures
(2002-05-01)
Wu, CC
;
Lin, CJ
;
應用數學系
;
電子工程學系及電子研究所
;
Department of Applied Mathematics
The free-carrier absorption in ultrathin wires fabricated from III-V semiconductors such as n-type InSb has been investigated for the case where the electrons are scattered either by polar optical phonons or acoustic phonons. We study the interaction of longitudinal polar optical phonons with electrons and have neglected the interaction between electrons and transverse optical phonons in solids. The energy band of electrons in semiconductors is assumed to be nonparabolic. The scattering mechanisms of the interaction between electrons and phonons we consider here come from (a) electron-polar-optical-phonon scattering, (b) electron-acoustic-phonon scattering, and (c) piezoelectric scattering in semiconductors. Results are shown that the free-carrier absorption coefficient for the deformation-potential coupling is much larger than that for the piezoelectric coupling. It is also shown that the free-carrier absorption coefficient for the electron-polar-optical-phonon scattering is smaller than that for the electron-acoustic-phonon scattering. However, the free-carrier absorption coefficient increases quite slowly with the photon frequency for the electron-acoustic-phonon scattering. This is not the same result as that for the quasi-two-dimensional semiconducting structures. (C) 2002 Published by Elsevier Science B.V.
Effect of nonparabolic bands on impurity-limited mobility of semiconducting thin wires in n-type germanium
(1998)
Wu, CC
;
Lin, CJ
;
應用數學系
;
電子工程學系及電子研究所
;
Department of Applied Mathematics
The impurity-limited mobility of semiconducting thin wires for nonparabolic structures in n-type Ge has been investigated by scattering from ionized impurities with doping arsenic. The scattering is coming from the background impurities or from the uniform distribution of remote impurities. Results are shown that the impurity-limited mobility due to the scattering from background impurities increases slowly and monotonically with increasing temperature for nondegenerate semiconductors at low temperatures. This is the same qualitative property as that for an ordinary three-dimensional semiconducting structure at low temperatures. However, the mobility due to the scattering from remote impurities increases rapidly with temperature and appears much larger than that from background impurities. It is also shown that the mobility decreases rapidly and monotonically with the wire radius of semiconducting thin wire for the scattering from background impurities or remote impurities. For degenerate semiconductors, the impurity-limited mobility decreases monotonically with the wire radius for the scattering from background impurities, but the mobility does not change with the wire radius quite clearly except a discontinuous point in the neighborhood of wire radius d < 100 Angstrom for the scattering from remote impurities.
Effect of nonparabolicity on free-carrier absorption in n-type InSb films for polar optical phonon scattering
(1999-03-01)
Wu, CC
;
Lin, CJ
;
應用數學系
;
電子工程學系及電子研究所
;
Department of Applied Mathematics
The free-carrier absorption in n-type InSb films has been studied for quantum well structures fabricated from III-V semiconducting materials where the polar optical phonon scattering is predominant. We consider here two special cases: the electromagnetic radiation is polarized parallel to the layer plane and perpendicular to the layer plane separately. The energy band of electrons in semiconductors is assumed to be nonparabolic. Results show that when the electromagnetic radiation is polarized parallel to the layer plane, the free-carrier absorption coefficient is independent of temperature in a small quantum well region such as d < 30 Angstrom, but the absorption coefficient oscillates with the quantum well and depends upon the temperature in the region of larger quantum wells. When the electromagnetic radiation is polarized perpendicular to the layer plane, the dependence of the free-carrier absorption coefficient on the quantum well and temperature becomes quite complicated. (C) 1999 Elsevier Science B.V. All rights reserved.
Effect of phonon scattering on free-carrier absorption in quantum well structures
(1996-04-01)
Wu, CC
;
Lin, CJ
;
應用數學系
;
電控工程研究所
;
Department of Applied Mathematics
The free-carrier absorption has been studied for quantum well structures fabricated from III-V semiconductors such as it-type InSb films when the acoustic phonon scattering is dominant. The energy band of carriers in semiconductors is assumed to be nonparabolic. The scattering mechanisms of phonons with carriers in semiconductors are considered for the deformation-potential coupling and the piezoelectric coupling separately. Results show that the free-carrier absorption coefficient in n-type InSb films depend upon the polarization of the radiation field relative to the direction normal to the quantum well structures, the photon frequency, the film thickness and the temperature. It is also found that the free-carrier absorption coefficient could be complex due to the interaction of the radiation field and the photon field with carriers in semiconductors. Thus, the index of refraction of semiconducting films could be changed due to this carrier-phonon-photon interaction.
Effective parallelization techniques for non-uniform loops
(1998)
Pean, DL
;
Wu, CC
;
Chua, HT
;
Chen, C
;
資訊科學與工程研究所
It is known that the parallelism of non-uniform dependence loops is difficult to extract and is not effectively explored by the existing parallelization methods. In this paper, we propose new techniques to transform non-uniform dependence loops efficiently, based on their irregularity, by which more parallelism can be explored directly and effectively. Several effective mechanisms, including parallelization part splitting, partial parallelization decomposition, irregular loop interchange and growing pattern rt detection are created to exploit more parallelism degree for non-uniform loop structures. Compared with other existing methods, our new approach gives better performance. When the loop bounds is increased from 5 to 50, based on our evaluations, the speedup achieves 3.25 to 19.8 times better than that of the uniformization technique; and from 1.5 to 8.33 times better than that of the minimum dependence distance tiling technique. We evaluate our mechanisms in our simulation environment for various conditions and discuss the performance of them in this paper.
Effects of nitrogen plasma treatment on tantalum diffusion barriers in copper metallization
(2003-02-01)
Wu, WF
;
Ou, KL
;
Chou, CP
;
Wu, CC
;
機械工程學系
In this study, the barrier properties of ultrathin Ta, TaN, and nitrogen plasma-treated Ta films were investigated by Cu/Ta(N)/Si structure. The barrier properties were evaluated by sheet resistance, film stress, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Nitrogen plasma-treated Ta films possess better barrier performance than sputtered Ta and TaN films. The sheet resistance of Cu/Ta/Si and Cu/TaN/Si increases, apparently, after annealing at 600 and 625degreesC, respectively. The Cu/30 min plasma-treated Ta/Si is fairly stable up to annealing at 700degreesC for 1 h. Diffusion resistance of the plasma-treated Ta barrier is more effective. It is believed that a new amorphous layer forms on the surface of Ta film after plasma treatment. The new amorphous layer possesses some nanocrystalline Ta2N phases with lattice constant 0.305 nm. It is believed that the amorphous layer containing some nanocrystals can alleviate Cu diffusion into the Si substrate and, hence, improve barrier performance. (C) 2003 The Electrochemical Society.