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991.
Jae-Shin Lee Min-Sun Keel Shin-Il Lim Suki Kim 《Electronics letters》2000,36(23):1907-1908
Conventional CMOS charge pump circuits have some current mismatching characteristics. The current mismatch of the charge pump in the PLLs generates a phase offset, which increases spurs in the PLL output signals. In particular, it reduces the locking range in wide range PLLs with a dual loop scheme. A new charge pump circuit with perfect current matching characteristics is proposed. By using an error amplifier and reference current sources, one can achieve a charge pump with good current matching characteristics. It shows nearly perfect current matching characteristics over the whole VCO input range, and the amount of the reference spur is <-75 dBc in the PLL output signal. The charge pump circuit is implemented in a 0.25 μm CMOS process 相似文献
992.
In a wireless system that supports multimedia services, each traffic requires different quality of service (QoS) at both communication on radio links and connection admission. We initially derive the uplink capacity satisfying the QoS constraint on radio links in a multiclass multicode code-division multiple-access (CDMA) system. Based on the derived capacity, the number of channel elements, which is one of the system resources, is determined. Then, we define the QoS parameters associated with connection processes. To guarantee the defined QoS at the connection level, under given channel elements, we propose a channel-assignment scheme with dynamic priority adjustment (DPA). The proposed scheme gives multipriority to different traffic classes. Real-time classes can preempt non-real-time classes with restricted preemptive priority. Such restriction is regulated by preemption-free code channels and a buffer threshold for non-real-time classes. Among real-time classes, different priorities are assigned to each traffic class by code reservation parameters. These multipriority parameters are dynamically adjusted in order to guarantee different QoS requirements. We analyze the DPA scheme by the matrix-geometric method, and evaluate the performance of each traffic class. The results show that the proposed scheme flexibly guarantees QoS depending on traffic loading condition and achieves high channel utilization. 相似文献
993.
Unsupervised image classification, segmentation, and enhancementusing ICA mixture models 总被引:7,自引:0,他引:7
An unsupervised classification algorithm is derived by modeling observed data as a mixture of several mutually exclusive classes that are each described by linear combinations of independent, non-Gaussian densities. The algorithm estimates the data density in each class by using parametric nonlinear functions that fit to the non-Gaussian structure of the data. This improves classification accuracy compared with standard Gaussian mixture models. When applied to images, the algorithm can learn efficient codes (basis functions) for images that capture the statistically significant structure intrinsic in the images. We apply this technique to the problem of unsupervised classification, segmentation, and denoising of images. We demonstrate that this method was effective in classifying complex image textures such as natural scenes and text. It was also useful for denoising and filling in missing pixels in images with complex structures. The advantage of this model is that image codes can be learned with increasing numbers of classes thus providing greater flexibility in modeling structure and in finding more image features than in either Gaussian mixture models or standard independent component analysis (ICA) algorithms. 相似文献
994.
Jong-Nam Kim Dae-Kap Kang Sung-Cheal Byun Il-Lo Lee Byung-Ha Ahn 《Broadcasting, IEEE Transactions on》2002,48(1):43-46
We propose a new as well as fast full search (FS) motion estimation algorithm for video coding. The computational reduction comes from sequential rejection of impossible candidates with derived formula and subblock norms. Our algorithm reduces more the computations than the FS motion estimation algorithms previously developed 相似文献
995.
K. C. Chen A. Telang J. G. Lee K. N. Subramanian 《Journal of Electronic Materials》2002,31(11):1181-1189
To better understand the effect of repeated reverse stress in solder joints, a new testing method was developed. Tin-silver
solder joints were fabricated, constrained between Cu blocks, and then subjected to repeated shear loading in a tensile tester.
Constant strain amplitudes were applied to simulate service conditions. However, large loads were used to accelerate the damage
accumulation. Microstructural features of the damage were very similar to those found with studies on thermomechanical fatigue
(TMF) of small, single shear lap samples. Concentrated-shear banding or striations were observed to form along Sn dendrites.
The load behavior of the solder with each cycle and during hold times at the extreme strain amplitude was consistent with
damage accumulating with each successive cycle. Effects of strain amplitude, hold times at the stress extremes, number of
cycles, and solder-joint thickness were found to play significant roles on the stress-strain behavior and surface damage. 相似文献
996.
Jong-Sen Lee Grunes M.R. Schuler D.L. Pottier E. Ferro-Famil L. 《Geoscience and Remote Sensing, IEEE Transactions on》2006,44(1):176-187
A new concept in polarimetric synthetic aperture radar (POLSAR) speckle filtering that preserves the dominant scattering mechanism of each pixel is proposed in this paper. The basic principle is to select pixels of the same scattering characteristics to be included in the filtering process. To achieve this, the algorithm first applies the Freeman and Durden decomposition to separate pixels into three dominant scattering categories: surface, double bounce, and volume, and then unsupervised classification is applied. Speckle filtering is performed using the classification map as a mask. A single-look or multilook pixel centered in a 9 /spl times/ 9 window is filtered by including only pixels in the same and two neighboring classes from the same scattering category. This filter is effective in speckle reduction, while perfectly preserving strong point target signatures, and retains edges, linear, and curved features in the POLSAR data. The effect of speckle filtering on scattering characteristics, such as entropy, anisotropy, and alpha angle, will be discussed. 相似文献
997.
Ok I. Hyoung-sub Kim Manhong Zhang Chang-Yong Kang Se Jong Rhee Changhwan Choi Krishnan S.A. Tackhwi Lee Feng Zhu Thareja G. Lee J.C. 《Electron Device Letters, IEEE》2006,27(3):145-147
In this letter, we studied the effects of post-deposition anneal (PDA) time and Si interface control layer (ICL) on the electrical characteristics of the MOS capacitor with high-/spl kappa/ (HfO/sub 2/) material on GaAs. Thin equivalent oxide thickness (EOT<3 nm) with excellent capacitance-voltage (C-V) characteristics has been obtained. The thickness of the Si ICL and PDA time were correlated with C-V characteristics. It was found that high temperature Si ICL deposition and longer PDA time at 600/spl deg/C improved the C-V shape, leakage current, and especially frequency dispersion (<5%). 相似文献
998.
Bai W.P. Lu N. Ritenour A. Lee M.L. Antoniadis D.A. Kwong D.-L. 《Electron Device Letters, IEEE》2006,27(3):175-178
In this letter, we report successful fabrication of germanium n-MOSFETs on lightly doped Ge substrates with a thin HfO/sub 2/ dielectric (equivalent oxide thickness /spl sim/10.8 /spl Aring/) and TaN gate electrode. The highest peak mobility (330 cm/sup 2//V/spl middot/s) and saturated drive current (130 /spl mu/A/sq at V/sub g/--V/sub t/=1.5 V) have been demonstrated for n-channel bulk Ge MOSFETs with an ultrathin dielectric. As compared to Si control devices, 2.5/spl times/ enhancement of peak mobility has been achieved. The poor performance of Ge n-MOSFET devices reported recently and its mechanism have been investigated. Impurity induced structural defects are believed to be responsible for the severe degradation. 相似文献
999.
Seung Won Kim Yong Tae Lee Sung Ik Park Ho Min Eum Jae Hyun Seo Heung Mook Kim 《Broadcasting, IEEE Transactions on》2006,52(2):137-146
Digital On-Channel Repeater (DOCR) can be used for Single Frequency Networks (SFN's). It is much simple and low cost compared to Distributed Transmitter which needs Studio to Transmitter Link (STL). However, traditional DOCR has one of those defects such as a power limit, a long time system processing delay or a poor output signal quality. In order to overcome all of those defects, we introduce Equalization DOCR (EDOCR) which regenerates the original 8-VSB output signal with relatively short time system processing delay. Lab. and Field test results show that the EDOCR can eliminate the loop-back signal up to 5.5 dB with 5.5 /spl mu/s system processing delay. By using EDOCR, we can save spectrum resources and extend coverage areas. 相似文献
1000.
Kyoung-Sik Im Jae-HyokKo Suk-Jin Kim Chan-Hee Jeon Chang-Su Kim Ki-Tae Lee Han-Gu Kim Il-Hun Son 《Microelectronics Reliability》2006,46(9-11):1664-1668
This paper presents a novel ESD strategy for non-volatile memory (NVM) programming pin in a 0.13um/30V technology. Suggested scheme can provide not only a major current discharge path to protect the internal circuit from ESD damage but also a voltage clamping function to prevent the soft error of programmed data during the ESD event. It has been validated by TLP experiments and TCAD simulation. 相似文献