Browsing by Author "Lee, WC"

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A fully all-planar integrated Ka-band FSK transceiver module
(2001)
Lee, CJ
;
Hung, TP
;
Lin, SC
;
Wu, HS
;
Tsai, CY
An open RFIC (Radio Frequency Integrated Circuit) architecture employing ACSS (Advanced Coplanar Strips System) guiding technology is presented in this paper. This approach can integrate all the RF front-end components in one module using conventional PCB (printed circuit board) fabrication process. A 10 Mb/s FSK signal is upconverted to 30.18 GHz and 30.28 GHz and broadcasted through a cone-shaped antenna at power level of 10 dBm. The received signal is directly converted to baseband by even harmonic quadrature mixer, which shows a great isolation of 30 dB between RF and LO signal. The measured waveforms of the reported transceiver demonstrate the potential of constructing the wireless system with all-planar integrated circuits.
A three-intensity technique for polarizer-sample-analyser photometric ellipsometry and polarimetry
(1998-08-21)
Chao, YF
;
Lee, WC
;
Hung, CS
;
Lin, JJ
;
交大名義發表
This work presents a novel three-intensity-measurement technique to determine the ellipsometric parameters psi and Delta in a polarizer-sample-analyser photometric ellipsometer. This technique can be employed to correct the azimuthal misalignment of the analyser with respect to the plane of incidence. By performing two sets of measurements with this technique with the polarizer's azimuth at +45 degrees and -45 degrees, respectively, we can simultaneously determine the azimuthal deviation of the polarizer and further improve the ellipsometric measurements. Applying this technique in the transmission mode allows us to obtain the phase retardation and the optical axis of a waveplate at the same time.
A unified fast algorithm for cosine modulated filter banks in current audio coding standards
(1999-12-01)
Liu, CM
;
Lee, WC
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資訊工程學系
;
Department of Computer Science
Current audio coding standards, such as MPEG-I layers 1-3, MPEG-II layers 1-4, MPEG-IV, and AC-3, have adopted for compression various forms of the cosine modulated filter banks (CMFBs). It is demonstrated that all modulated cosine transforms can be divided into two modules-the permutation and discrete cosine transform. The derived discrete cosine transforms are either type II, type III, or type IV. A fast computing algorithm is proposed that will compute all three types of transforms uniformly. The new fast algorithm has good features with regard to regularity, complexity, and general applicability.
Bit allocation for advanced audio coding using bandwidth-proportional noise-shaping criterion
(2003)
Liu, CM
;
Lee, WC
;
Chien, CT
;
資訊工程學系
;
Department of Computer Science
The bandwidth-proportional noise-shaping criterion has been proposed to be the optimum bit allocation criterion in the sense of minimizing segmental masking-to-noise ratio [1]. A single loop bit allocation has been developed for ISO/IEC MPEG-1layer 3 (MP3) [2] to reduce the complexity over the existing two nested loop method for MP3 encoder. Also, the allocation method also leads to the better compression quality. This paper extends the allocation method to the ISO/IEC MPEG-2/4 Advanced Audio Coding (AAC) [3] [4]. This paper derives the perceptual bandwidth for the scale factor bands, provides the bit consumption trade-off to transmit the bits for the scale factors, and illustrates an efficient sectioning method on the Huffman codebook. All these methods jointly integrate with the bit allocation method to improve the quality and the computing complexity of the widely used AAC reference encoder, FAAC [5].
Bit allocation method for AC-3 encoder
(1998-08-01)
Liu, CM
;
Lee, SW
;
Lee, WC
;
資訊工程學系
;
Department of Computer Science
Dolby AC-3 is an audio coder selected in the United State high definition television (HDTV) standards and widely adopted for the audio codec in DVD films. For audio coder, the complexity of the audio encoders is always higher than that of the decoders. A main module leading to the higher complexity is the bit allocation process. The objective of the bit allocation is to allocate restricted bits to encoded information. Since that AC-3 coder has adopted a floating point representation which the magnitude of each spectral line is represented with an exponent and a mantissa, the bit allocation process not only has to decide the suitable quantization method for the mantissa similar to the process in other coding standards such as MPEG1, but also the exponent strategies and hence the parameters in psychoacoustic models. This coding process has been referred to as a hybrid coding [5] and has led to immense complexity for an encoder. This paper proposes an efficient method for the bit allocation process.
Channel backscattering characteristics of strained PMOSFETs with embedded SiGe source/drain
(2005)
Lin, HN
;
Chen, HW
;
Ko, CH
;
Ge, CH
;
Lin, HC
Channel backscattering ratios of PMOSFETs with various embedded SiGe source/drain structures are analyzed in terms of the scattering theory We found that both the backscattering ratio and injection velocity are greatly influenced by the location and recess depth of SiGe source/drain. Although the strain-enhanced injection velocity is beneficial to the current gain, the accompanying backscattering ratio increase adversely impacts the overall performance, and therefore a trade-off exists between injection velocity and backscattering ratio during the optimization of such strain technique. The mechanism of increased backscattering ratio under uniaxial compressive strain is also investigated.
Channel backscattering characteristics of uniaxially strained nanoscale CMOSFETs
(2005-09-01)
Lin, HN
;
Chen, HW
;
Ko, CH
;
Ge, CH
;
Lin, HC
Channel backscattering characteristics of uniaxially strained nanoscale CMOSFETs are reported for the first time. Channel backscattering ratio increases and decreases under uniaxial tensile and compressive strain, respectively. It is found that in sub-100-nm devices, strain-induced modulation of carrier mean-free path for backscattering and reduction in kBT layer thickness are responsible for the different behaviors of backscattering ratio. Nevertheless, the source-side injection velocity improves irrespective of the strain polarities. The impact of channel backscattering ratio on drive current is also analyzed in terms,of ballistic efficiency and injection velocity.
Channel-width dependence of low-frequency noise in process tensile-strained n-channel metal-oxide-semiconductor transistors
(2006-02-06)
Lu, MP
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Lee, WC
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Chen, MJ
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Low-frequency noise measurement in process tensile-strained n-channel metal-oxide-semiconductor field-effect transistors yields the density of the interface states, exhibiting a decreasing trend while decreasing the channel width. This finding corroborates the group of P-b centers caused by the lattice mismatch at (100) Si-SiO2 interface as the origin of the underlying interface states. The inverse narrow width effect appears to be insignificant, substantially confirming the validity of the noise measurement. The present noise experiment therefore points to the enhancement of the tensile strain in the presence of channel narrowing, which in turn reduces the lattice mismatch.
Characteristics of deep levels in As-implanted GaN films
(2002-09-02)
Lee, L
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Lee, WC
;
Chung, HM
;
Lee, MC
;
Chen, WH
Hall, current-voltage and deep level transient spectroscopy measurements were used to characterize the electric properties of n-type GaN films implanted with As atoms. After 800 degreesC thermal annealing for 60 min, one additional deep level located at E-C-0.766 eV was found in the films. We presume this induced trap is an arsenic-related point defect, most likely antisite in nature. (C) 2002 American Institute of Physics.
Design of bandpass filters with parallel three-line coupled microstrips
(2001)
Kuo, JT
;
Shih, E
;
Lee, WC
;
電信工程研究所
;
Institute of Communications Engineering
Bandpass filters are designed based on parallel coupled three-line microstrip structures. The relation between the circuit parameters of a three-line coupled microstrip section and an admittance inverter is established. A design graph for substrate with epsilon(r) = 2.2 is provided. Two Chebyshev filters, of order 2 and 1dB passband ripple, with fractional bandwidths 40% and 60% are fabricated and measured. Good agreement between prediction and measurement is obtained.
Design of the coupling schemes for the AC-3 coder in stereo coding
(1998-08-01)
Liu, CM
;
Lee, WC
;
Juang, SY
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資訊工程學系
;
Department of Computer Science
When applying the Dolby AC-3 coder for the stereo music compression, the coupling scheme that combines the two channels stereo audio signals in high frequency into one channel is the key technology for the Dolby AC-3 to achieve the bit rates lower than 96x2 kbits/sec while preserving high stereo audio quality. This paper proposes four coupling methods for the AC-3 encoder. These four methods vary with the complexity and performance. These four methods are compared through both subjective and objective tests. These four coupling methods are also combined with the dithering scheme and examined through subjective and objective tests. The result shows that the dithering scheme can effectively ease the coupling artifacts and enhance the audio quality.
Efficient generation of isosurfaces in volume rendering
(1995-11-01)
Chuang, JH
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Lee, WC
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交大名義發表
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資訊工程學系
;
National Chiao Tung University
An efficient method for extracting isosurfaces from volume data is proposed. The method utilizes a modified branch-on-need octree to bypass regions of no current interest. In addition, during the generation of triangle meshes neighboring triangles are merged according to certain criteria. Methods are also given to significantly reduce the space required for octrees. The method is more efficient and generates far fewer triangles than the marching cube algorithm. The performance of the proposed method is compared with that of several existing methods.
Fast perceptual convolution for room reverberation
(2003)
Lee, WC
;
Liu, CM
;
Yang, CH
;
Guo, JI
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資訊工程學系
The FIR-based reverberators, which convolve the input sequence with an impulse response modelling the concert hall, have better quality compared to the IIR-based approach. However, the high computational complexity of the FIR-based reverberators limits the applicability to most cost-oriented system. This paper introduces a method that uses perceptual criterion to reduce the complexity of convolution methods for reverberation. Also, an objective measurement criterion is introduced to check the perceptual difference from the reduction. The result has shown that the length of impulse response can be cut off by 60% without affecting the perceptual reverberation quality. The method is well integrated into the existing FFT-based approach is have around 30% speed-up.
High frequency reconstruction for band-limited audio signals
(2003)
Liu, CM
;
Lee, WC
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Hsu, HW
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資訊工程學系
;
Department of Computer Science
Current existing digital audio signals are always restricted by sampling rates and bandwidth fit for the various storages and communication bandwidth. Take for example the widely spread mp3 tracks encoded by the standard MPEG1 layer 3. The audio bandwidth in MP3 is restricted to 16 kHz due to the protocols constraints defined. This paper presents the method to reconstruct the lost high frequency components from the band-limited signals. Both the subjective and objective measures have been conducted and shown the better quality. Especially, the important objective measurement by the perceptual evaluation of audio quality system, which is the recommendation system by ITU-R Task Group 10/4 has proven a significant quality improvement.
Liquid crystal alignment with a photo-crosslinkable and solvent-soluble polyimide film
(2000-05-15)
Lee, WC
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Hsu, CS
;
Wu, ST
;
應用化學系
;
Department of Applied Chemistry
A new photo-crosslinkable and solvent-soluble polyimide containing cinnamate side chains (PICA) was developed for aligning nematic liquid crystals (LCs). Good LC alignment was achieved by exposing a long-wave linearly polarized ultraviolet (LPUV) light to the PICA film. The LC alignment direction is found perpendicular to the polarization axis of the incident LPUV light. The uniform alignment of LC molecules induced by PICA Films remains intact after being heated at 85 degreesC for 450 hours. A small pretilt angle on the PICA film was generated by the double exposure method.
M/S coding based on allocation entropy
(2003)
Liu, CM
;
Lee, WC
;
Hsiao, YH
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資訊工程學系
;
Department of Computer Science
Main/Side (M/S) coding is a module deigned to reduce the channel irrelevancy and redundancies for multichannel coding in current audio standards. However, the success of this module relies on the careful design on four aspects: M/S decision, psychoacoustic model for the M/S channels, bits allocated between the M/S channels, and bit allocation in the M/S channels. This paper presents an efficient M/S method well designed from the four aspects. We conduct the experiments through the MP3 encoder to show the better quality and complexity than the Lame.
Material and ultrafast optoelectronic properties of furnace-annealed arsenic-ion-implanted GaAs
(1998-09-01)
Lin, GR
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Chen, WC
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Chang, CS
;
Chao, SC
;
Wu, KH
Structural, electrical, and ultrafast optical properties of furnace-annealed arsenic-ion-implanted GaAs (GaAs:As+) has been investigated for its applications in ultrafast optoelectronics, From these studies, we determine that GaAs substrates implanted with 200-keV arsenic ions at 10(16) ions/cm(2) and furnace-annealed at 500 degrees C-600 degrees C would have recovered its crystallinity, be highly resistive, and exhibit picosecond photo-excited carrier lifetimes. The duration of the electrical pulses generated by photoconductive switches (PCS's) fabricated on the optimized material was approximate to 4 ps, The risetime (10%-90%) and 1/e falltime were, respectively, approximate to 2 and 3 ps, These results were measurement-system limited, We estimated the actual response to be approximate to 2 ps, consistent with a photo-excited carrier lifetime of approximate to 1.8 ps. The peak responsivity was greater than or equal to 4x10(-3) A/W. The dark current for the GaAs:As+ PCS biased at 40 V was as low as 5 nA. The break down field was higher than 150 kV/cm, These characteristics are comparable to those of state-of-the-art photoconductors such as LT-GaAs.
Photo-alignment of liquid crystals using a crosslinked discotic film
(2001-02-01)
Wu, LH
;
Lee, WC
;
Hsu, CS
;
Wu, ST
;
應用化學系
A new photo-alignment layer using a crosslinked discotic compound was demonstrated. This discotic compound exhibits excellent solubility in common organic solvents, the possibility of low temperature processing and good thermal stability. A linearly polarized long wavelength ultraviolet (LPUV) light (lambda = 350 nm) was used to initiate the crosslinking process and induce liquid crystal alignment on the discotic film surface. The induced LC directors were found parallel to the electric field direction of the LPUV light. A 1.2 degrees pre-tilt angle was achieved using a single exposure at a 30 degrees oblique angle.
Photo-induced liquid crystal alignment with discotic films
(2000-10-01)
Wu, LH
;
Lee, WC
;
Hsu, CS
;
Wu, ST
;
應用化學系
Photo-induced liquid crystal alignment using cross-linked discotic compounds was demonstrated. These discotic compounds exhibit good solubility in common organic solvents, 60 degreesC processing temperature and excellent thermal stability. A linearly polarized long wave ultraviolet light (lambda = 350 nm) was used to initiate the cross-linking process which, in turn, induces liquid crystal alignment on the discotic film surface. The polarity of discotic compounds plays an important role in affecting the pretilt angle of the liquid crystal alignment. A pretilt angle of 1 +/- 0.4 degrees was obtained using single exposure at oblique angle. Potential application of this new photo-alignment film for low temperature poly-silicon thin-film-transistor liquid crystal display is foreseeable.
Planar realization of low phase noise 15/30 GHz Oscillator/Doubler using surface mount transistors
(2003-01-01)
Lee, WC
;
Lin, SC
;
Tzuang, CKC
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電信工程研究所
;
Institute of Communications Engineering
This paper presents the application of a novel high-Q planar waveguide resonator for microwave oscillator design. The waveguide cavity is made in printed-circuit-board process, first using a routed cut followed by a plated via-through-hole. Measurements show that the oscillator stabilized by the resonator delivers an output power of 14 dBm at 15 GHz and a phase noise of -98 dBc/Hz at 100 kHz offset from the carrier, under 5-V single bias. Experiments indicate the predominance of the waveguide resonator by a 13-dB phase noise improvement at 100 kHz offset against the microstrip oscillator.