Browsing by Author "Wu, LK"

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A fast algorithm for computing field radiated by an insulated dipole antenna in dissipative medium
(1996-12-01)
Wu, LK
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Su, DWF
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Tseng, BC
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交大名義發表
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傳播研究所
A fast algorithm for determining the near-field characteristics of an insulated dipole antenna (IDA) embedded in a homogenous dissipative medium is described in this paper. A thin-wire-approximation type of analysis is followed here. In this case, radiation is considered to originate from a filamentary current flowing along the axis of the dipole, which is surrounded immediately hy the ambient dissipative medium, The translational symmetry inherent in the resultant radiation integrals is then exploited to speed up the computation. In one case studied, the basic thin-wire approach that uses no symmetry property is found to yield accurate results in approximately 380 times less CPU time than the traditional King-Casey approach, In another case, use of symmetry property further reduces the CPU time by a factor of 7; additional reduction in CPU time is possible by taking into account the near-field nature of the problem.
A scalable noise de-embedding technique for on-wafer microwave device characterization
(2005-10-01)
Cho, MH
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Huang, GW
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Wang, YH
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Wu, LK
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電信工程研究所
In this letter, we present a scalable and efficient noise de-embedding procedure, which is based on transmission-line theory and cascade configurations, for on-wafer microwave measurements of silicon MOSFETs. The proposed de-embedding procedure utilizes one open and one thru dummy structures to eliminate the parasitic effects from the probe pads and the input/output interconnects of a device-under-test (DUT), respectively. This method can generate the scalable distributed interconnect parameters to efficiently and precisely remove the redundant parasitics of the DUTs with various device sizes and arbitrary interconnect dimensions.
A shield-based three-port de-embedding method for microwave on-wafer characterization of deep-submicrometer silicon MOSFETs
(2005-09-01)
Cho, MH
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Huang, GW
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Wu, LK
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Chiu, CS
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Wang, YH
A general three.-port S-parameter de-embedding method using shield-based test structures for microwave on-wafer characterization is presented in this paper. This method does not require any physical equivalent-circuit assumption for the surrounding parasitics of a device-under-test. We use one open and three thru dummy devices to remove the parasitic components connected to the gate, drain, and source terminals of a MOSFET. By shielding the lossy silicon substrate, the cross-coupling from port to port can be significantly mitigated, and thus, the parasitics of probe pads and interconnects at each port can be separately subtracted. The MOS transistor and its corresponding dummy structures fabricated in a 0.18-mu m CMOS process were characterized up to 20 GHz. Compared with the two-port cascade-based de-embedding method, the proposed three-port de-embedding procedure can further eliminate the parasitics associated with the dangling leg in the source terminal. The impacts of the accuracy of the de-embedding technique on device modeling and simulation are also discussed.
A theoretical investigation ofthe resonance damping performance of magnetic material coating in Power/Ground plane structures
(2005-11-01)
Wu, LK
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Tseng, CH
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傳播研究所
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Institute of Communication Studies
Power bus structure, consisting of two parallel solid power and ground planes separated by an insulator, behaves as a cavity resonator at high frequencies. Noise on the power bus, due to a sudden change in the current drawn by an active component, can appear as an undesired spatial fluctuation in the voltage between power and ground, especially at resonant frequencies of the resultant cavity, which may lead to problems in signal integrity, excessive delays, false switching, and radiated emission. These resonances can be suppressed by introducing high-frequency loss into the structure. This paper investigates a simple method to reduce self-/transfer impedance of power/ground planes for mitigating power/ground bounce in high-speed printed circuit board design by adding a thin layer of magnetic material coating to the inside-facing surfaces of copper power and ground plates to increase their effective high-frequency surface impedance. The increased surface impedance will increase the attenuation constant of the propagating wave inside the cavity that benefits reduction of cavity's quality factor (Q factor). The simulation results obtained from a modified cavity resonator model show that increasing surface impedance can dramatically reduce self- and transfer impedances at board resonant frequencies.
Bias effect on the growth of carbon nanotips using microwave plasma chemical vapor deposition
(2002-07-22)
Tsai, CL
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Chen, CF
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Wu, LK
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材料科學與工程學系
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Department of Materials Science and Engineering
Carbon nanotips with a high-aspect ratio were directly grown on Pt films. Carbon nanotips grew up to 5.4 mum length and 64 nm diameter under a -120 V bias. Compared to the hollow structure of carbon nanotubes, transmission electron microscopy images indicate its solid body, which is made of graphite. Carbon nanotips possess good field emission characteristics, that is, a turn-on field of 1.5 V/mum and 761 muA/cm(2) under 2.2 V/mum. The Pt films provide a good conduction path for electron transport from the cathode to the emission site and do not act as catalysts. (C) 2002 American Institute of Physics.
Design and analysis of an asymmetrically fed insulated coaxial slot antenna with enhanced tip-heating performance
(2000-08-01)
Wu, LK
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Su, DWF
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傳播研究所
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Institute of Communication Studies
In this paper, a novel use of an asymmetrically fed insulated coaxial slot antenna (ICSA) type of applicator for interstitial microwave hyperthermia that simultaneously exhibits good impedance matching and enhanced tip-heating performances is presented. Theoretical analysis reveals that by making the distal arm much shorter than the other arm of the antenna, charge densities distributed over the distal arm of the antenna increase significantly. This, in turn, can result in the-radial electric-field component becoming the dominant contributor to the specific absorption rate (SAR) over the distal arm side of the heating region and, therefore, the achievement of enhanced tip-heating performance, With the length of the longer arm chosen to be slightly longer than a quarter-wavelength, good impedance matching and enhanced tip-heating performances are achieved when the length of the shorter distal arm is reduced to no more than 25% of that of the longer arm, Good agreements observed between theoretical and measured SAR patterns for two ICSA's designed for operation at 915 and 433 MHz, respectively, confirm the validity of the design method.
Design of miniaturized common-mode filter by multilayer low-temperature co-fired ceramic
(2004-11-01)
Tseng, BC
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Wu, LK
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傳播研究所
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Institute of Communication Studies
A miniaturized common-mode filter composed of multiple substrates with positive and negative coils formed on alternate substrates is proposed in this paper. The pattern of each positive coil is interlaced with that of each negative coil, whereby when the positive and negative coils are alternately stacked, the positive coil do not overlap the negative coil. With such offset configuration, the parasitic capacitance introduced between positive and negative traces is reduced, so the thickness of each substrate can be decreased and the size of the entire filter is effectively reduced. Good agreements between simulated and measured results are demonstrated. Further, the effectiveness of this filter is confirmed by eye diagram and radiation emission measurements.
Embedded passive components for printed-circuit boards
(1999)
Wu, LK
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Tseng, BC
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Liao, LC
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電信工程研究所
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Institute of Communications Engineering
Demand for significant size reduction of circuitry used to build various portable products has increased rapidly in recent years. While significant strides have been made in the integration of active components, only little progress has been made in the integration of passive components. Together with the increasing circuit complexities to meet the increasing demand on a product's functionality, number of passive components used in a typical portable product has increased significantly in recent years and may account for 70-80% of the total part count. The embedded passives technology that was developed recently is aimed at integrating various passive components at the printed-circuit board level. By integrating these passives, manufacturers may obtain the following advantages: (1) a dramatic reduction in the overall part count, (2) improved wireability due to the elimination of vias, (3) improved reliability due to the elimination of solder joints, and (4) improved frequency response due to the elimination of parasitic inductance.
Input impedance characteristics of coaxial slot antennas for interstitial microwave hyperthermia
(1999-03-01)
Su, DWF
;
Wu, LK
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傳播研究所
;
Institute of Communication Studies
In this paper, a transmission-line type of input impedance model originally developed by King ct al. [4] for the insulated dipole antenna embedded in a homogeneous dissipative medium is extended to the case of insulated coaxial slot antenna, Physical construction of the latter indicates the presence of additional current path(s) inside the feed line, which shall lead to the shortening of its resonance length, This effect is taken into account in the impedance model and verified by experiments, Furthermore, a simple strategy for optimizing the applicator's impedance-matching performance is also described and verified. Excellent agreements observed between theoretical and measured S-11 data indicate that these models can be relied upon when designing an efficient applicator for interstitial microwave hyperthermia.
Integral passives in multi-dielectric substrate
(2000)
Wu, LK
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Tseng, BC
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Liao, LC
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電信工程研究所
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Institute of Communications Engineering
Integral passives technology has the potential for achieving denser packaging, more efficient manufacturing processes, better reliability and future replacement of many surface mount devices which will result in savings of volume, mass and cost To improve the circuit performance and obtain greater benefits of the integral passives, multi-dielectric substrates with layer-specific dielectric constant and thickness can be used to design the integral passives. With these different material characteristics we design various integral capacitors in a 6-layer printed wiring boards and then extract various circuit parameters associate with the frequency-dependent equivalent circuit models. From which a comparison between the experimentally measured characteristics and the simulated results of an RF amplifier will be demonstrated.
Spectral analysis of blood circulation based on the viewpoint of resonance
(2006-04-01)
Wei, CC
;
Lo, PC
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Wu, LK
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電控工程研究所
;
電信工程研究所
In this paper, we present a novel idea for analyzing blood circulation that is viewed as an electrical-driving, mechanical-pumping mechanism. Considering the electrocardiogram (ECG) and blood pressure wave (BPW) as the input and output signals of the system, we aim to quantify the spectral behavior of blood circulation from the viewpoint of resonance. First, the power spectrum of the ECG coincides well with that of the BPW for healthy subjects, but deviates significantly front the BPW's for vascular patients. Second, bispectral analysis demonstrates a strong phase coupling between ECG and BPW in healthy Subjects and a weaker coupling for subjects with vascular problems. Third, the transfer function for healthy subjects exhibits a flatter magnitude than that for patients. In addition, we propose a resonance circuit model of the spectral domain to represent blood circulation. The quality factor also exhibits better resonance characteristics for the healthy group than for the patient group.
System analysis of blood circulation based on coherence power transfer: From electrical driving to mechanical vibration
(2006-04-01)
Wei, CC
;
Lo, PC
;
Wu, LK
;
電控工程研究所
;
電信工程研究所
We analyze blood circulation based on the basis of the system viewpoint and coherence power transfer from electrical energy (ECG) to mechanical power (blood pressure wave). The coherent oscillation between the driving signal and the vibration of the cardiovascular system is investigated by coherence function and the perturbations of the system are found. In addition, we develop a mathematical equation to describe the phenomenon. The average peak coherence value S for the first live harmonics is utilized as an index to quantify the power coherence effect. The evaluated p-value (< 0.01) reveals that the distinction of power coherence between the healthy subjects and cardiovascular patients is significant. Consequently, we conclude that if the S approaches a value close to one, the output is almost completely attributed to input and fewer perturbation signals influence the system: therefore, the cardiovascular system stays in a better condition. Conversely, if S approaches a value less than one, larger perturbations will worsen the cardiovascular system condition.