Browsing by Author "Chen, SH"

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2 V-operated InGaP-AlGaAs-InGaAs enhancement-mode pseudomorphic HEMT
(2005-02-01)
Chu, LH
;
Chang, EY
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Chen, SH
;
Lien, YC
;
Chang, CY
A low-voltage single power supply enhancement-mode InGaP-AlGaAs-InGaAs pseudomorphic high-electron mobility transistor (PHEMT) is reported for the first time. The fabricated 0.5 x 160 mum(2) device shows low knee voltage of 0.3 V, drain-source current (I-DS) of 375 mA/mm and maximum transconductance of 550 mS/mm when drain-source voltage (V-DS) was 2.5 V. High-frequency performance was also achieved; the cut-off frequency(F-t) is 60 GHz and maximum oscillation frequency(F-max) is 128 GHz. The noise figure of the 160-mum gate width device at 17 GHz was measured to be 1.02 dB with 10.12 dB associated gain. The E-mode InGaP-AlGaAs-InGaAs PHEMT, exhibits a high output power density of 453 mW/mm with a high linear gain of 30.5 dB at 2.4 GHz. The E-mode PHEMT can also achieve a high maximum power added efficiency (PAE) of 70%, when tuned for maximum PAE.
2.4 V-operated enhancement mode PHEMT with 32 dBm output power and 61 % power efficenciecy
(2001)
Chen, SH
;
Chang, EY
;
Lin, YC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A 2.4 V operated enhancement-mode pseudormorphic high electron mobility transistors (E-PHEMTs) with high output power and power-added-efficiency (PAE) have been developed. With optimally designed epitaxial structure and gate recess process, the E-PHEMT shows high power performance and high power gain. Under 2.4 V bias at 1.9 GHz, the E-PHEMT shows maximum output power of 32.25 dBm and maximum power-added efficiency of 61.45% with linear power gain of 13.93 dB when the device was tuned for maximum output power match. When tuned for maximum output power added efficiency, the E-PHEMT can achieve a maximum PAE of 78.51%. The developed E-PHEMT with superior power performance is one of the candidates for power amplifiers used for 2.4 V-operated 3G wireless communication system.
2.4 V-operated enhancement-mode power PHEMTs for personal handy-phone system application
(2001)
Chen, SH
;
Chang, EY
;
Lin, YC
;
Lee, CS
;
友訊交大聯合研發中心
Enhacement-mode pseudomorphic high electron mobility transistors (E-PHEMTs) were developed for low voltage wireless communication applications. Under drain bias of 3.6 V, the device delivered a high output power density of 265.25 mW/mm (29.5dBm) with a power-added-efficiency (PAE) of 50.54 %. Under 1.9GHz pi/4-shifted quadrature phase shift keying(QPSK) modulation signal, the 3.36 mm devices meet personal handy-phone system (PHS) specification at an output power level of 22.42 dB with PAE of 35.12% under 2.4 V drain bias. The E-PHEMTs developed are adequate for low-voltage-operated PHS application.
A 1.2-V operation power pseudomorphic high electron mobility transistor for personal handy phone handset application
(2000-10-15)
Chang, EY
;
Lee, DH
;
Chen, SH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A 1.2 V GaAs power pseudomorphic high electron mobility transistors (PHEMT's) for personal handy phone system (PHS) handset application was developed. The power PHEMT has a dual delta doped AlGaAs/InGaAs/GaAs based structure with compact device layout. The 6.72 mm device exhibits maximum power added efficiency (PAE) of 43.62% at 1.2V drain bias with an output power of 22.18 dBm. Under 1.9 GHz pi /4-shifted quadrature phase shift keying (QPSK) modulated PHS signal, the device shows an adjacent channel leakage power (P-adj) Of -56.86 dBc at 600 kHz apart from the center frequency and a linear efficiency of 41.31%. This is the first report on the 1.2-V operation power PHEMT for PHS handset application so far.
A fair and space-efficient mutual exclusion
(2005)
Chen, SH
;
Huang, TL
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資訊工程學系
;
Department of Computer Science
For shared memory systems with time and resource constraints such as embedded real-time systems, mutual exclusion mechanism that is both fair and space-efficient can be very useful. In this paper, we present a boundedbypass algorithm using only two shared variables, regardless of the number of contending processes, by operation fetch&store as well as atomic read/write. To achieve the same level of fairness, we show that, by the same set of operations, two shared variables are necessary, and therefore our algorithm is space-optimal.
A GaAs/AlAs wet selective etch process for the gate recess of GaAs power metal-semiconductor field-effect transistors
(2001-01-01)
Chang, EY
;
Lai, YL
;
Lee, YS
;
Chen, SH
;
材料科學與工程學系
A highly selective wet chemical etch process for gate recess of the GaAs power metal-semiconductor field effect transistors (MES FETs) was developed. The power MESFETs used in this study were epitaxially grown devices with a 20 Angstrom A1As etch-stop layer for gate recess. The selective etch process using citric acid/potassium citrate/hydrogen peroxide solution was studied. A selectivity better than 3800:1 was achieved for GaAs/A1As layers. This selective etch was applied both to high-power, high-voltage power MESFETs and low-voltage large-periphery power MESFETs. For high-power applications, the 14.7 mm device had a breakdown voltage of 22 V. When tested at 1.88 GHz with a drain bias of 10 V, it provided a maximum output power of 38.8 dBm and a maximum power-added efficiency of 52.5%. For low-voltage applications, the 19.8 mm device was tested under IS-95 code-division multiple access (CDMA) modulation at 1.88 GHz with a drain bias of 3.5 V. Under CDMA modulation, the device showed an output power of 28.03 dBm with an adjacent channel power rejection of -29.6 dBc at 1.25 MHz offset frequency. Both devices also showed excellent uniformity in pinch-off voltages. (C) 2000 The Electrochemical Society. S0013-4651 (00)03-053-6. All rights reserved.
A high power enhancement-mode pseudomorphic high electron mobility transistor with 2.5 W output power and 64.5 % efficiency at 3 V
(2002)
Chen, SH
;
Chang, EY
;
Lin, YC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A 3-V operated enhancement-mode pseudomorphic high electron mobility transistor (E-PHEMT) with high output power and high efficiency has been developed. The E-PHEMT has total gate width of 20 mm and gate length. of 0.5 mum. When the power performance was evaluated at 1.9 GHz, the E-PHEMT shows a saturation output power of 34.1 dBm (2.57 W) with power-added efficiency (PAE) of 64.5 % and power gain of 10.2 dB at 3 V bias. The linear gain under this testing condition is 14.9 dB. The E-PHEMTs developed have excellent power performance and are suitable for power amplifier application for cellular handsets.
A high-performance Min-Nan/Taiwanese TTS system
(2003)
Kuo, WC
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Zhong, XR
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Wang, YR
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Chen, SH
;
電信工程研究所
In this paper, the implementation of a high-performance Min-Nan/Taiwanese TTS system is presented. The system can convert both Min-Nan/Taiwanese texts, represented in a hybrid Han-Lo written form, and Chinese texts into natural Taiwanese speeches. It is an improved version of the system developed previously [11]. Improvements include: the add of a "Chinese-to-Min-Nan/Taiwanese" lexicon to solve the OOV problem and to increase the ability of processing Chinese text; the use of explicit tone sandhi rules to ease the learning of prosody generation; a further processing of the training database to detect all breaks not associated with PMs; and the use of four RNNs to separately generate four types of prosodic parameters. The system is implemented by software and runs in real-time on PC. An informal subjective listening test confirmed that the system performed well. All synthetic speeches sounded natural for well-tokenized Min-Nan/Taiwanese texts and for automatic tokenized Chinese texts.
A low noise composite-channel metamorphic HEMT for wireless communication applications
(2003)
Lu, CY
;
Chen, KS
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Lee, HM
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Chang, EY
;
Chen, SH
A composite-channel Metamorphic high electron mobility transistor (MHEMT) was developed for low noise high linearity application. The MHEMT was grown by Molecular Beam Epitaxy (MBE) on GaAs substrates with InAlAs graded buffer. The composite-channel layers in the MHEMT include a top In0.55Ga0.45As layer, a middle In0.67Ga0.33As layer, and a bottom In0.55Ga0.45As layer. The design of this structure provides better electron confinement in the channel with less impact ionization as compared to conventional dual delta doped MHEMTs. This results in devices with higher linearity and drain to gate voltage as compared to the conventional metamorphic HEMTs. The 0.25x160 mum(2) device with the novel channel structure exhibits a maximum frequency of oscillation f(max) of 290 GHz and a current gain cut-off frequency f(t) of 110 GHz. The noise figure of the device at 6 GHz is 0.23 dB and the associated gain was 15.06 dB. The IP3 of the device at 6 GHz is 19.67 dBm. The composite channel metamorphic HEMT shows great potential for high linearity and low noise application at high frequencies.
A low power design on diffusive interconnection large-neighborhood cellular nonlinear network for giga-scale system application
(2004-01-01)
Chen, SH
;
Wu, CY
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電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, the diffusive interconnection large neighborhood cellular nonlinear network (LN-CNN) with low power dissipation and small chip area is proposed and analyzed. In the proposed new architecture, the number of gain blocks can be reduced by merging template A model and template B model together with suitable adjustment. All the gain blocks are based on simple current-mirror circuits so the cell has small chip area and save more power. Thus the new architecture and circuits are suitable for large array LN-CNN implementation for giga-scale system applications. The functions of LN-CNN are verified by HSPICE simulation and the LN-CNN chip will be fabricated to verify the simulation results.
A Mandarin text-to-speech system
(1996)
Hwang, SH
;
Chen, SH
;
Wang, YR
;
交大名義發表
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電信工程研究所
In this paper, the implementation of a high-performance Mandarin TTS system is presented. The system is composed of four main parts: text analysis (TA), prosodic information generation (PIG), waveform table (WT) of 411 base-syllables, and PSOLA-based waveform synthesis (PSOLA). In TA, a statistical model based method is first employed to automatically tag the input text to obtain the word sequence and the associated part-of-speech (POS) sequence. A lexicon containing about 80000 words is used in the tagging process. Then the corresponding base-syllable sequence is found and used to get from WT the basic wave-form sequence. Some linguistic features used in PIG are also extracted in TA, In PIG, a four-layer recurrent neural network (RNN) is employed to generate some prosodic information including pitch. contour, energy level, initial duration and final duration of syllable as well as inter-syllable pause duration. Finally, in PSOLA the basic waveform sequence is modified using the prosodic information to generate output synthetic speech, The whole system is implemented by software on a PC/AT 486 with a 16-bit Sound Blaster add-on card. Only 3.2 Mbyte memory space is required. It can synthesize speech in real-time for any input Chinese text. Informal listening tests by many native Chinese living in Taiwan confirmed that the synthetic speech sounded very fluent and natural.
A metamorphic high electron-mobitity transistor with reflowed submicron T-Gate for high-speed optoelectronics applications
(2003)
Lien, YC
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Chang, EY
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Chu, LX
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Chang, HC
;
Lee, CS
A metamorphic high electron-mobility transistor (HEMT) manufactured with reflowed submicron T-gate using E-beam lithography for high-speed optoelectronics applications is developed. The In0.53Al0.47As/InGaAs HEMT uses InxAl1-xAs as the buffer layer between GaAs substrate and the InP lattice-matched HEMT structure. The T-gate developed has a gate length of 0.1 mum. The fabricated metamorphic HEMT has a saturation drain current of 280mA/mrn and a transconductance of 840mS/mm at V-DS=1.2V Noise figure for 160 mum gate-width device is less than 1 dB and the associated gain is up to 14dB at 18GHz. The device demonstrates a cut-off frequency f(T) of 150GHz and a maximum frequency f(MAX) up to 350GHz. The metamorphic HEMT developed has the potential for high-speed optoelectronics applications.
A method to determine the higher order polar anchoring coefficients for the non-twisted liquid crystal cells
(2005-08-01)
Hsu, JS
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Hsieh, MC
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Yang, CL
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Liang, BJ
;
Chen, SH
We propose a method to determine the higher order polar anchoring coefficients for the non-twisted liquid crystal cells. The surface anchoring energy density was determined by measuring the phase retardations as a function of applied voltage. We extended the Rapini-Papoular model and obtained the coefficients of the first and the second terms by analyzing the measured phase retardations with the simulated curves for the homogeneous and homeotropic cells. A discussion of the experimental results is given.
A model-based tone labeling method for Min-Nan/Taiwanese speech
(2004)
Kuo, WC
;
Wang, YR
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Chen, SH
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電信工程研究所
;
Institute of Communications Engineering
in this paper, a model-based tone labeling method for Min-Nan/Taiwanese speech is proposed. It takes the mean and shape of syllable pitch contour as two modeling units and considers some major affecting factors that control their variations. By using the EM algorithm to estimate all parameters of the pitch mean and shape models from a speech database, we can decide the best tone sequences pronounced in all utterance of the database. Experimental results showed that it outperformed the VQ classification method which suffers from the interferences resulted from neighboring syllables and from the global prosodic phrase pattern.
A modular RNN-based method for continuous Mandarin speech recognition
(2001-03-01)
Liao, YF
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Chen, SH
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電信工程研究所
;
Institute of Communications Engineering
A new modular recurrent neural network (MRNN)-based method for continuous Mandarin speech recognition (CMSR) is proposed. The MRNN recognizer is composed of four main modules. The first is a sub-MRNN module whose function is to generate discriminant functions for all 412 base-syllables. It accomplishes the task by using four recurrent neural network (RNN) submodules. The second is an RNN module which is designed to detect syllable boundaries for providing timing cues in order to help solve the time-alignment problem. The third is also an RNN module whose function is to generate discriminant functions for 143 intersyllable diphone-like units to compensate the intersyllable coarticulation effect. The fourth is a dynamic programming (DP)-based recognition search module. Its function is to integrate the other three modules and solve the time-alignment problem for generating the recognized base-syllable sequence. A new multilevel pruning scheme designed to speed up the recognition process is also proposed. The whole MRNN can be trained by a sophisticated three-stage minimum classification error/generalized probabilistic descent (MCE/GPD) algorithm. Experimental results showed that the proposed method performed better than the maximum likelihood (ML)-trained hidden Markov model (HMM) method and is comparable to the MCE/GPD-trained HMM method. The multilevel pruning scheme was also found to be very efficient.
A new duration modeling approach for Mandarin speech
(2003-07-01)
Chen, SH
;
Lai, WH
;
Wang, YR
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電信工程研究所
;
Institute of Communications Engineering
In this paper, a new duration modeling approach for Mandarin speech is proposed. It explicitly takes several major affecting factors as multiplicative companding factors (CFs) and estimates all model parameters by an EM algorithm. Besides, the three basic Tone 3 patterns (i.e., full tone, half tone and sandhi tone) are also properly considered via using three different Us to separate their affections on syllable duration. Experimental results showed that the variance of the syllable duration was greatly reduced from 180.17 to 2.52 frame(2) (1 frame =5 ms) by the syllable duration modeling to eliminate effects from those affecting factors. Moreover, the estimated Us of those affecting factors agreed well to our prior linguistic knowledge. Two extensions of the duration modeling method are also performed. One is the use of the same technique to model initial and final durations. The other is to replace the multiplicative model with an additive one. Lastly, a preliminary study of applying the proposed model to predict syllable duration for TTS is also performed. Experimental results showed that it outperformed the conventional regressive prediction method.
A new structure of large-neighborhood cellular nonlinear network (LN-CNN)
(2003-01-01)
Cheng, CH
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Chen, SH
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Lin, LJ
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Huang, KH
;
Wu, CY
In this paper, a novel Large-Neighborhood Cellular Nonlinear Network (LN-CNN) structure is proposed and analyzed. The proposed LN-CNN structure can realize both A and B templates with more than two neighborhood layers without complex direct connections between neural cell and neighboring cells. In both A and B templates, the first layer is defined by 4 neighboring cells located at the 4 corners of a diamond shape whereas the second layer is defined by 8 cells. In realizing the 12 template coefficients of a template, only 8 connections are required as compared to 12 connections in the conventional CNN structure. Thus the required chip area for synaptic connection can be reduced. Using the proposed LN-CNN structure, the LN-CNN functions, such as noise removing, Muller-Layer arrowhead illusion, and connected component detection, have been successfully realized and verified in MATLAB simulations. The constraints on the realized templates and the template coefficients in the third or higher layers are analyzed and discussed. Based upon he above successful simulation results, the application of the proposed LN-CNN structure to the design of LN-CNN Universal Machine (LN-CNNUM) is quite feasible. The related research will be conducted in the future.
A novel syllable duration modeling approach for Mandarin speech
(2001)
Lai, WH
;
Chen, SH
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, a novel syllable duration modeling approach for Mandarin speech is proposed. It explicitly takes several main affecting factors as multiplicative companding parameters and estimates all model parameters by an EM algorithm. Experimental results showed that the variance of the observed syllable duration was greatly reduced from 183.4 frame(2) (1 frame = 5 ms) to 18.5 frame(2) by eliminating effects from these affecting factors. Besides, the estimated companding values of these affecting factors agreed well to our prior linguistic knowledge. A preliminary study of applying the proposed model to predict syllable duration for TTS is also performed. Experimental results showed that it outperformed the conventional regressive prediction method. Lastly, an extension of the approach to incorporate initial and final duration modeling is presented. This leads to a better understanding of the relation between the companding factors of initial and final duration models and those of syllable duration model.
A prototype of Mandarin speech telephone number inquiry system
(1997)
Lu, PR
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Hong, WT
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Chiang, SL
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Wang, YR
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Chen, SH
In this paper, a prototype of Mandarin speech telephone number inquiry system is implemented on a PC platform with a Dialogic D/41D card and a 16-bit Soundblaster card as the telephone line interface. It is an integration of a speaker-independent, isolated-word speech recognition sub-system and a text-to-speech (TTS) subsystem, and is operating under Windows 95. The vocabulary to be recognized comprises 1922 names of bank and insurance companies with word lengths ranging from 2 to 14 syllables. A recognition rate of 92.6% was achieved. All output speech messages are responded by the TTS sub-system.
A robust training algorithm for adverse speech recognition
(2000-04-01)
Hong, WT
;
Chen, SH
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電信工程研究所
;
Institute of Communications Engineering
In this paper, anew robust training algorithm is proposed for the generation of a set of bias-removed, noise-suppressed reference speech HMM models in adverse environment suffering from both channel bias and additive noise. Its main idea is to incorporate a signal bias-compensation operation and a PMC noise-compensation operation into its iterative training process. This makes the resulting speech HMM models more suitable to the given robust speech recognition method using the same signal bias-compensation and PMC noise-compensation operations in the recognition process. Experimental results showed that the speech HMM models it generated outperformed both the clean-speech HMM models and those generated by the conventional k-means algorithm for two adverse Mandarin speech recognition tasks. So it is a promising robust training algorithm. (C) 2000 Elsevier Science B.V. All rights reserved.