Browsing by Author "Lo, YC"

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A push mechanism for GPRS supporting private IP addresses
(2003-01-01)
Lin, YB
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Lo, YC
;
Rao, HCH
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資訊工程學系
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Department of Computer Science
General Packet Radio Service (GPRS) provides packet switched data service for mobile users. However, the existing GPRS specification does not provide the push mechanism and it is difficult to support GPRS services such as call termination (incoming call) for wireless voice over IP (VoIP). Based on short message service, this paper proposes a push mechanism for GPRS supporting private IP addresses. Our approach does not need to modify the existing GPRS structure.
Micro-fabrication of hemispherical poly-silicon shells standing on hemispherical cavities
(2001)
Lin, CH
;
Lo, YC
;
Hsu, WS
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機械工程學系
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Department of Mechanical Engineering
In the current paper, the fabrication process of a novel proposed hemispherical polysilicon shell standing on a hemispherical silicon cavity is demonstrated. This micro-fabrication process combines both bulk and surface micromachining, which include the isotropic wet etching, a novel mask design, the thick photo resist coating and exposure, and high-aspect-ratio curved sacrificial technique. In isotropic wet etching of a hemispherical cavity, the optimal concentration of etchant is experimentally determined along with adequate ultrasonic vibration during wet etching to produce the circle-like of hemispherical cavity. The conventional alignment mark, which will be destroyed during the rather long isotropic wet etching process, is replaced by a novel mask design with the second alignment mark. Also, for a deep hemispherical cavity larger than 100mum, the traditional photo resist can not be coated on the corner surface well. The thick photo resist, AZ4620, is found to be able to overcome this problem and be successfully exposed all through its bottom surface. Furthermore, the deposited sacrificial layer materials (PSG) on this cavity will usually result in thinner layer near the corner. In addition, the curved gap of PSG layer has the feature with high-aspect-ratio. These make the PSG etching difficult. Therefore, two steps etching process with two different hydrofluoric concentrations are used to release the PSG with 2mum thickness and 150mum arc length.
Structure design of a 2-D high-aspect-ratio resonant microbearn accelerometer
(2005-07-01)
Hwang, DH
;
Chin, KP
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Lo, YC
;
Hsu, WS
;
機械工程學系
An accelerometer with concise structure having a resonant microbeam to measure 2-D acceleration is proposed. This structure is configured with a central proof mass suspended by four symmetrical and orthogonal high-aspect-ratio (HAR) microbeams. This dual-axis design is able to decouple a two-axis signal from a 2-D acceleration. An analytical model relating the linear relationship between the acceleration and the associated resonant frequency shift of microbeam is derived, and a finite element analysis (FEA) is also performed to confirm this model. The FEA result also shows that there is little cross talk between x and y directions of measurement, meaning that this structure is able to clecouple a planar 2-D acceleration into two independent acceleration components, and therefore the 1-D analytical model can be used to evaluate the 2-D acceleration on the x-y plane. In addition, the model is verified by testing results of one conventional dual-axis natural frequency shifted microaccelerometer (DFSM). The simulation result also shows that the sensitivity of the proposed HAR accelerometer is triple that of a conventional DFSM. (c) 2005 Society ofPhoto-Optical Instrumentation Engineers.