Browsing by Author "Wu, CS"

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An efficient collision resolution scheme for wireless multiple access
(1998)
Chen, PN
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Wu, CS
;
Ma, GK
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電信工程研究所
;
Institute of Communications Engineering
This paper presents a contention resolution scheme for multiple random access based on tree algorithms. The proposed scheme, called Dynamic Collision Resolution (DCR), is a variation of the tree algorithm. Given that plural users are transmitting packets to a shared communication medium, the free algorithm will divide the transmitting users into n parts upon detecting a collision condition and, in the later retransmission, collisions will only occur in between the users that fall into the same part. It was well known that the optimal value of n is 3 under the condition that n is fixed and the number of users is infinite. The proposed DCR scheme adopts a dynamically change on the value of n for a better contention resolution. The performance is evaluated through the simulation over a finite number of users and the result shows that the DCR scheme gives a non-trivial improvement on the tree algorithms under a moderate number of users.
Characterization and modeling of out-diffusion of cesium, manganese and zinc impurities from deep ultraviolet photoresist
(2000)
Ko, FH
;
Wang, MY
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Wang, TK
;
Yang, CC
;
Huang, TY
The novel radioactive tracer technique was applied to investigate the migration of cesium, manganese and zinc impurities from deep ultraviolet photoresist into underlying substrate. Two important process parameters, viz., baking temperatures and substrate types (i.e., bare silicon, polysilicon, silicon oxide and silicon nitride), were evaluated. Our results indicated that the migration ratios were all below 6%, irrespective of baking temperatures and substrate types. The substrate types did not appear to strongly affect the metallic impurity out-diffusion from deep ultraviolet photoresist. However, solvent and/or water evaporation due to temperature change was found to have a significant effect on metal migration. The net driving force of impurity changes with temperature and the impurity diffusion can be classified into four types. Based on the proposed types, the obtained migration ratios can be realized. A new model, together with a new parameter, was proposed to describe the out-diffusion behavior of impurities from deep ultraviolet photoresist. The diffusion profile of photoresist was depicted based on diffusion equations and the migration ratios. This model could explain the migration ratios of metallic impurities in photoresist layers under various baking conditions.
Geometric shape dependence of coercivity for patterned magnetic thin films
(2000-02-01)
Wu, TH
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Wu, JC
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Wu, CS
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Chen, BM
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Shieh, HPD
The micro-strips with patterned magnetic domains using electron beam lithography have been made to study the geometric shape dependence of coercivity. The size of the micro-strip is 10 mu m x 30 mu m with 0.5 mu m periods hole arrays pattern. Arrays with different types of geometry, such as square- circle-, and ellipse-shapes have been made. amorphous rear-earth transition-metal (RE-TM) thin films with magnetic perpendicular anisotropy were deposited on the microstrips. The extraordinary Hall effect has been employed to measure the hysteresis loop and the coercivity of the sample. We have found that for the same deposited material, the magnitude of coercivity for various shapes are dissimilar. For example, the coercivity of the ellipse-shaped hole arrays is much larger than the coercivity of the square-shaped hole arrays. In addition, we observed that the coercivity of the patterned sites was larger than the sites without patterns for RE-dominated compounds and the coercivity of the patterned sites was smaller than the sites without patterns for TM-dominated compounds. The magnetic moments canting between RE and TM subnetworks will be used to explain the observed phenomena. (C) 2000 Elsevier Science B.V. All rights reserved.
Magnetoresistance anomaly in DyFeCo thin films
(2001-06-01)
Wu, JC
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Wu, CS
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Wu, TH
;
Chen, BM
;
Shieh, HPD
Microstructured rare-earth-transition-metal DyFeCo films have been investigated using magnetoresistance and extraordinary Hall-effect measurements. The Hall loops reveal variation of coercive fields depending on the linewidth and the composition of the films. The magnetoresistance curves, with changes up to as high as 1.3%, show positive/negative magnetoresistance peaks centered on the coercive fields depending on the linewidth of the films only. The variation of the coercivity can be attributed to the magnetic moment canting between the Dy and FeCo subcomponents and the existence of the diverged magnetization on the edges, and the anomalous magnetoresistance peaks observed are discussed with the existing theories. (C) 2001 American Institute of Physics.
Microstructure effects on quantum efficiency in PtSi/p-Si(100) Schottky barrier detector
(2001-02-15)
Horng, GJ
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Chang, CY
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Chang, T
;
Ho, C
;
Wu, CS
The microstructure effects on the performance of the PtSi Schottky barrier detector (SBD) have been investigated in detail. The growth temperatures were ranged from 350 to 550 degreesC. The thickness of the PtSi film measured by high resolution transmission electron microscopy (HRTEM) is around 4 nm. The electron diffraction pattern shows an intermingling of both (1 (1) over bar 0) and (I (2) over bar 1) orientations when the PtSi film is formed at 350 degreesC. However, the diffraction patterns show only (1 (2) over bar1) orientation when the PtSi films are formed above 450 degreesC. It was found that the electrical barrier height of the Schottky barrier detector formed at 350 degreesC is about 0.02 eV higher than that formed above 450 degreesC. The microstructure of the PtSi film does not change even though the formation temperature is further increased to 550 degreesC. Nevertheless, the higher the formation temperature, the larger is the grain size. It was also observed that the grain size does not change the electrical barrier height. However, the quantum efficiency of the detector is much higher if the grain size is larger. The results indicate that the quantum efficiency of the detector can be improved if the PtSi film has (1 2 1) orientation and larger grain size. (C) 2001 Elsevier Science B.V. All rights reserved.
Performance analysis of noncoherent digital delay locked loops for direct sequence spread spectrum systems with Doppler shift and quantized adaptation
(2004-11-01)
Sheen, WH
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Chang, MJ
;
Wu, CS
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電信工程研究所
;
Institute of Communications Engineering
The noncoherent second-order digital delay locked loop (DLL) with the presence of Doppler shift is investigated. The loop performance such as lock-in range, transient response, mean time-to-lose lock (MTLL), and mean square tracking error (MSE) are analyzed. The analysis is unique in two respects. First, MTLL and MSE are evaluated more accurately than by previous methods. Second, the impact of quantized adaptation on the loop performance is examined for digital DLL that was neglected previously. Numerical results show that: 1) the quantized adaptation may significantly alter the loop behaviors, including the lock-in range, transient responses, MTLL, and MSE; and 2) the traditional analysis based on Gaussian approximation may result in a large error in performance evaluation when quantized adaptation is taken into account.