Browsing by Author "Chen, SK"

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Active feedback microstrip leaky wave antenna-synthesiser design with suppressed back lobe radiation
(1999-04-01)
Shih, YC
;
Chen, SK
;
Hu, CC
;
Jou, CF
;
傳播研究所
The design of an active leaky-wave antenna which integrates the antenna with a feedback synthesiser is introduced. The measurement result shows that the antenna has very low back lobe radiation compared with that of traditional single-terminal feeding leaky-wave antennas. Single frequency measurement shows that the radiated power differmce between the main beam and back lobe is >15 dB at 8.2 GHz For the designed feedback synthesiser antenna, the measured radiated power difference between the main beam and back lobe is >15dB at 9.25 GHz, and the scanning angle is similar to 5 degrees as the synthesiser frequency sweeps from 9.25 to 9.37 GHz.
Fault-tolerant and progressive transmission of images
(2005-12-01)
Chen, SK
;
Lin, JC
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資訊工程學系
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Department of Computer Science
A fault-tolerant progressive image transmission method is proposed. The advantages include the following: (1) Unlike most progressive methods, the image is divided into n parts with equal importance to avoid worrying about which part is lost or transmitted first. (2) If the image is a secret image, then the transmission can use n distinct channels (one shared result per channel), and intercepting up to r(1) - 1 channels by the enemy (r(1) <= (...) <= r(k) <= n are all pre-set constants) will not reveal any secret. Meanwhile, the disconnection up to n - rk channels will not affect the lossless recovery of the secret image. (c) 2005 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.
Fully normalized spherical cap harmonics: Application to the analysis of sea-level data from TOPEX/POSEIDON and ERS-1
(1997-05-01)
Hwang, CW
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Chen, SK
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交大名義發表
;
土木工程學系
;
National Chiao Tung University
We introduce two sets of fully normalized harmonics for the spectral analysis of functions defined on a spherical cap. The harmonics are the products of Fourier functions and the fully normalized associated Legendre functions of non-integer degree. Using Sturm-Liouville theory for boundary-value problems, we present two convenient and stable formulae for computing the zeros of the associated Legendre functions that form two sets of orthogonal functions. Formulae for the stable numerical evaluation of the fully normalized associated Legendre functions of non-integer degree that avoid the gamma function are also derived. The result from the expansions of sealevel anomaly from altimetry into Set 2 fully normalized cap harmonics shows fast convergence of the series, and the degree variances decay rapidly without aliasing effects. The zero-degree coefficients (Set 2) of sea-level anomaly from TOPEX/POSEIDON (T/P) and ERS-1 indicate an El Nino event during 1993 January-1993 July, and a La Nina event during 1993 November-1994 July, although the ERS-1 result is less obvious. Ocean circulations over the South China Sea and the Kuroshio area are clearly identified with the low-degree expansions of sea-surface topography (SST) from T/P and ERS-1. A cold-core eddy of 4 degrees in diameter centred at 17.5 degrees N, 118 degrees E was detected with the expansion of SST from T/P cycle 47, and a property of the cap harmonics is used to compute this eddy's kinetic energy. The kinetic energy is at a low in winter and high in summer, and its variation seems to be periodic with an amplitude of 0.4 m(2) s(-2).
Hierarchical instruction encoding for VLIW digital signal processors
(2005)
Liu, CH
;
Lin, TJ
;
Chao, CM
;
Hsiao, PC
;
Lin, LC
VLIW-based architectures are very popular in high-performance DSP processors, for their relatively simpler implementations and more predictable execution times. But they need more program memory because of (1) the fixed-length instruction encoding, (2) NOP insertion due to limited parallelism, and (3) repetitive codes for loop unrolling. This paper describes a novel hierarchical instruction encoding that address these three problems to improve the VLIW code density. In our simulations, the proposed encoding scheme saves 61.4%-66.9% code sizes in highly parallel DSP kernels, and more savings can be expected for general programs. Besides, a simple decoding architecture is proposed and has been integrated into a 4-way VLIW DSP processor. The prototype is implemented in the 0.18um CMOS technology with its operating frequency at 208MHz.
Impact of nitrogen and/or fluorine implantation on deep-submicron Co-salicide process
(2002-08-01)
Chang, TY
;
Lei, TF
;
Chao, TS
;
Chen, SW
;
Kao, LM
In our previous study, using NF3 annealed poly-Si to improve gate oxide integrity for Co-silicide process has been proposed [SSDM, 1998, p. 164]. It is very interesting and important to know the mechanism of both F and N incorporation in the SiO2 and Co-salicide. In this study, F and/or N will be implanted into poly-Si with/without Co-salicide process, to identify the interaction of N and F in the SiO2 and Co-salicide process. In our work, we will describe the optimized structure and F/N incorporation for Co-silicide process. (C) 2002 Elsevier Science Ltd. All rights reserved.
Improvement of ultra-thin 3.3 nm thick oxide for co-salicide process using NF3 annealed poly-gate
(1999-04-01)
Chang, TY
;
Lei, TF
;
Chao, TS
;
Huang, CT
;
Chen, SK
To get high quality ultra-thin oxide is very important and difficult for IC industry now. Using NF3 annealed poly-Si gate to improve gate oxide integrity is described. However, reducing fate, source and drain parasitic resistance with gate lengths down to 0.2 mu m is another key point. Co-salicide process can successfully reduce the gate resistance even for a gate length of 0.075 mu m. Although, Co-salicide process has a leakage problem. Using NF3 annealing to prevent Co diffusing into gate oxide is described too. Results show that the optimal NF3 annealing significantly improves electrical characteristics of ultra-thin oxide and Co-salicide process in terms of leakage current and breakdown field, as compared to the samples without NF3 annealing.
Low contact resistance of poly-plug structure by in-situ HF-vapour cleaning
(2000-04-13)
Chen, JH
;
Lei, TF
;
Chao, TS
;
Su, TP
;
Huang, SJ
A low contact-resistance poly-plug structure realised by in-situ HF-vapour cleaning in a clustered tool is described. The native oxide in the contact area can be efficiently removed by the combination of an HF-dipping and in-situ HF-vapour cleaning process, resulting in a low specific contact resistance.
Novel programmable digital signal processor for multimedia applications
(2004)
Lin, LC
;
Lin, TJ
;
Lee, CC
;
Chao, CM
;
Chen, SK
This paper presents a novel DSP architecture for multimedia applications. The DSP core is a simple RISC processor from the programmer's view, which has a high-performance DSP unit and the applications can be easily targeted on the RISC shell to reduce the development time. Moreover, the DSP unit is itself a fully-programmable 4-way VLIW datapath, which has a novel ping-pong register file. To smooth the instruction execution of the two-level programmable DSP processor and improve the code density, we propose a hierarchical encoding scheme for variable-length instructions. The simulations show that our DSP has comparable performance with state-of-the-art DSP architectures, and the hierarchical instruction encoding saves 31%-64% code sizes compared to the fixed-length instruction encoding.
The CACTUS object server: Design and implementation issues
(1998)
Meng, IH
;
Yang, WP
;
Lin, SM
;
Chen, MA
;
Chen, SK
CACTUS is a compact and reliable object storage system based an peer-to-peer architecture with distributed transaction processing capability. The kernel is implemented with the multi-thread mechanisms to provide a high performance multi-transaction environment. All sites, installed with CACTUS, of the networked workstations are on an equal footing. The system can handle local and remote transactions including accessing remote objects or processing remote accesses. In this paper. we give an architectural overview of CACTUS and discuss some implementation issues. It mentions the special contributions such as transient large objects, the coarser lack granularity and its associated protocol. A cost model is developed to demonstrate that the new scheme yields performances which are superior in most common cases and inferior under certain situations.