Browsing by Author "Chang, Li-Ming"

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Design of Dual-Passband Microstrip Bandpass Filters With Multi-Spurious Suppression
(2010-04-01)
Jiang, Meshon
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Chang, Li-Ming
;
Chin, Albert
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A systematic design method for microstrip bandpass filters with both dual-passband response and multi-spurious suppression is proposed in this letter. The filter is composed of stepped impedance resonators (SIRs). A novel asymmetric SIR structure is proposed to effectively increase the degree of freedom in the dual-passband bandwidth design. As a consequence, the transmission zero of the coupling stage could be used to suppress the unwanted higher order spurious responses. A complete design procedure considering both the synthesis of passband responses and the suppression of spurious responses is also depicted in detail. A fifth order filter is designed and fabricated to demonstrate this idea. The measured results show that the upper stopband can have an attenuation level near 30 dB up to more than 20 GHz (8.16 f(0)).
Design of Dual-Passband Microstrip Bandpass Filters With Suppression of Higher Order Spurious Response
(2009)
Jiang, Meshon
;
Chang, Li-Ming
;
Chin, Albert
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper proposes a systematic design method for dual-passband microstrip bandpass filters composed of stepped impedance resonators (SIRs) with suppression of higher order spurious responses. A specific dual-band fractional bandwidth design graph must be built. The line widths of the SIR and the gap size between SIRs provide two freedoms for determining the realizable fractional bandwidth of the two passbands. The inherent transmission zeros of coupled SIRs are used to suppress the unwanted spurious responses. A complete design procedure considering both the synthesis of passband responses and the suppression of spurious responses is detailed depicted in this paper. The idea is verified by a fabricated experimental filter. The measured frequency responses shows that the spurious response can be suppressed below -35.4 dB and the upper band can be extended to 5.62 f(0) (13.77GHz).
Effect of backbone on the biaxial retardation of polyimide films in uniaxial stretch
(2007-05-15)
King, Jinn-Shing
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Whang, Wha-Tzong
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Lee, Wen-Chin
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Chang, Li-Ming
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材料科學與工程學系
A biaxial-retardation film prepared from the uniaxial-stretched polyimide (PI) film was developed for compensating the viewing angle of liquid-crystal displays. Good uniformity of in-plane bireffingence in well-stretched PI films was observed visually with two crossed polarizers. The prism coupling method was used to measure the n(x), n(y), n(z), and thickness of the stretched PI films. The birefringence variations of n, - n, (difference of refractive indices between x- and y-axes) and n(x) - n(z) during the stretching process were highly affected by PI structure. The polarizability tensors and intrinsic birefringences of the PI repeat units were estimated by Gaussian 98W. It was found that the stretch-induced birefringence is more related to the average polarizability per volume at the low elongation period. (C) 2006 Elsevier B.V. All rights reserved.
Plasmons-Enhanced Minority-Carrier Injection as a Measure of Potential Fluctuations in Heavily Doped Silicon
(2014-07-01)
Chen, Ming-Jer
;
Chen, Chuan-Li
;
Hsieh, Shang-Hsun
;
Chang, Li-Ming
;
電子工程學系及電子研究所
Well-known apparent electrical silicon bandgap narrowing in a heavily doped region of a bipolar transistor is observed by means of an enhanced minority-carrier injection experiment. In the region of interest, plasmons-induced potential fluctuations are existent in nature and hence constitute the origin of apparent bandgap narrowing. In this letter, we extract the underlying potential fluctuations directly from the enhanced minority-carrier injection experiment published in the literature. The core of the extraction lies in a combination of the two existing theoretical frameworks. First, the Gaussian distribution can serve as a good approximation of potential fluctuations. Second, no change can be made in the real bandgap between fluctuating conduction-and valence-band edges. Extracted potential fluctuations come from plasmons, as verified by our published temperature dependences of plasmons limited mobility in the inversion layer of MOSFETs as well as theoretical calculation results on bulk silicon. More importantly, this letter can deliver potential applications in the modeling and simulation area of nanoscale FETs (MOSFETs, FinFETs, and so forth) and bulk semiconductors.
Probing Long-Range Coulomb Interactions in Nanoscale MOSFETs
(2013-12-01)
Chen, Ming-Jer
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Chang, Li-Ming
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Wei, Sih-Yun
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Chen, Wan-Li
;
Yeh, Ting-Hsien
We have recently experimentally probed long-range Coulomb interactions due to plasmons in polysilicon gate of long-channel (1 mu m) MOSFETs. In this letter, we further probe those due to plasmons in the highly doped source and drain. Test vehicles include four more samples from the same manufacturing process but with small channel lengths (down to 33 nm). I-V's of devices are measured at two drain voltages of 0.05 and 1 V, in a temperature range of 292-380 K. Inverse modeling technique is applied to furnish calibrated doping profiles. The inversion layer electron effective mobility is thereby extracted, showing a decreasing trend with decreasing channel length. Such differences reflect more additional scatterers in the shorter devices. Mobility components limited by these additional scatterers are assessed using Matthiessen's rule. From the extracted temperature dependencies, we infer that the strength of source/drain plasmons increases with decreasing channel length. The errors of Matthiessen's rule are adequately dealt with. Corroborative evidence is given as well.
Structural effect on stretch-induced birefringence in polyimide films
(2007-10-01)
King, Jinn-Shing
;
Lee, Wen-Chin
;
Chang, Li-Ming
;
Whang, Wha-Tzong
;
材料科學與工程學系
Seven polyimides (Pls) of low glass transition temperature were synthesized and their films were uniaxially stretched to observe the variation in their in-plane birefringence (An). The intrinsic birefringences (triangle n degrees) of their polymer chains were also estimated using the experimental average refractive indices and computationally calculated polarizability tensors. The observed stretch-induced An was markedly affected by the PI structure. A model that shows a good fit to experimental data is proposed to predict the orientation degree of PI chains in different PI films. The model, when combined with the analysis of the estimated An's, is useful in explaining the behavior of stretch-induced triangle ns in PI films.
Temperature-Oriented Mobility Measurement and Simulation to Assess Surface Roughness in Ultrathin-Gate-Oxide (similar to 1 nm) nMOSFETs and Its TEM Evidence
(2012-04-01)
Chen, Ming-Jer
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Chang, Li-Ming
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Kuang, Shin-Jiun
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Lee, Chih-Wei
;
Hsieh, Shang-Hsun
On a 1.27-nm gate-oxide nMOSFET, we make a comprehensive study of SiO2/Si interface roughness by combining temperature-dependent electron mobility measurement, sophisticated mobility simulation, and high-resolution transmission electron microscopy (TEM) measurement. Mobility measurement and simulation adequately extract the correlation length lambda and roughness rms height Delta of the sample, taking into account the Coulomb-drag-limited mobilities in the literature. The TEM measurement yields the apparent correlation length lambda(m) and roughness rms height Delta(m). It is found that the following hold: 1) lambda approximate to lambda(m) for both the Gaussian and exponential models, validating the temperature-oriented extraction process; 2) the extracted Delta (similar to 1.3 angstrom for the Gaussian model and 1.0 angstrom for the exponential one) is close to that (similar to 1.2 angstrom) of Delta(m), all far less than the conventional values (similar to 3 angstrom) in thick-gate-oxide case; and 3) the TEM 2-D projection correction coefficient Delta(m)/Delta is approximately 1.0, which cannot be elucidated with the current thick-gate-oxide-based knowledge.