Browsing by Author "Wu, MJ"

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A constant power consumption CMOS LC oscillator using improved high-Q active inductor with wide rining-range
(2004)
Wu, MJ
;
Yang, JN
;
Lee, CY
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An improved CMOS high-Q active inductor and a constant power consumption oscillator with wide tuning-range are presented. The inductor using one feedback resistor results in a gain to improve the Q-value of the inductor and tune the inductance (L). Based on this inductor, a negative resistance LC-tuned oscillator with constant power consumption and wide tuning-range has been designed. The simulation results show that the improved active inductor can achieve the maximum Q-value of 3500. The power consumption of a constant value around 10mW exists in the oscillator. This oscillator also depicts a reasonable phase noise performance of -91dBc/Hz at 600 kHz from 0.8GHz to 3GHz range. Furthermore, the deviation of the phase noise is as small as 6dBc/Hz during this tuning-range.
A wavelet multiresolution compression technique for 3D stereoscopic image sequence based on mixed-resolution psychophysical experiments
(2000-07-01)
Chang, PR
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Wu, MJ
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電信工程研究所
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Institute of Communications Engineering
Three-dimensional visual communications, made through the use of stereoscopic images, are able to achieve total display realism. In order to create a 3D system with two images (left and right) that should be transmitted simultaneously, the large amount of information contained in the images should be reduced, and an efficient coding appropriate for stereoscopic images is developed. Stereoscopic image sequence compression involves the exploitation of the spatial redundancy between the left and right image frames to achieve the compression ratio higher than that are by the independent compression of the two frames. In order to further achieve the higher compression ratio, in this paper, we employ the mixed-resolution psychophysical experiments to the stereo image compression. The experiments have shown that a stereo image pair with one high-resolution image and one lower-resolution image is sufficient to provide good stereoscopic depth perception. Thus, one image sequence is compressed independent of the other sequence using the motion compensation, while the other sequence is estimated at a lower resolution from this stream using the low-resolution disparity compensation. To implement the mixed-resolution coding, a wavelet multiresolution framework has been adopted to facilitate such an estimation of motion and disparity vectors at different resolutions. Experimental results indicate that the compression ratio for a typical stereoscopic image sequence is about 90, without any significant loss in the perceived 3D stereoscopid image quality. (C) 2000 Elsevier Science B.V. All rights reserved.
Design of multicode CDMA systems for 3-D stereoscopic video over wireless ATM networks
(2000-03-01)
Chang, PR
;
Lin, CF
;
Wu, MJ
;
電信工程研究所
;
Institute of Communications Engineering
This paper investigates the application of multicode spread-spectrum code-division multiple-access (SS-CDMA) techniques to three-dimensional (3-D) stereoscopic video transmission over wireless asynchronous transfer mode (ATM) networks. Three-dimensional visual communications, made through the use of stereoscopic images, are able to achieve total display realism. Such services allow users to share the virtual reality (VR) world without any geographical restrictions. In order to create a 3-D system with two images (left and right) that should be transmitted over a bandlimited mobile channel simultaneously, a cost-effective Motion Picture Experts Group (MPEG)-based wavelet multiresolution coding with a joint motion and disparity compensation is developed to reduce a large amount of information contained in the images to meet the low-transmission rate limitation of mobile channels. However, the rapidly variable bit rate (VBR) characteristics of the MPEG-based 3-D videos seems a weakness to the transmission of such videos via a constant bit-rate (CBR) mobile channel. The ATM technique is especially well suited for VER MPEG-based 3-D video because of its ability to allocate bandwidth on demand to these services. However, since the mobile radio has a Limited channel capacity, the overall capacity of the traditional ATM-based SS-CDMA system may not be sufficient to accommodate the MPEG-based 3-D video services requested by the multiple mobile users simultaneously. To tackle this difficulty, a multicode CDMA technique is proposed to provide VER MPEG-based 3-D video services by varying the number of spreading codes assigned to the 3-D video to meet its dynamic throughput requirement. Powerful forward error correction (FEC) codes are necessary to protect the video data so that it can be successfully transmitted at an acceptable signal power level. Two separate FEC code schemes are applied to the header and payload of an ATM cell containing 3-D video data, respectively. The ATM cell header is protected by a relatively powerful FEC code to ensure correct delivery and low cell loss rate (CLR). On the other hand, the ATM cell payload is encoded for varying degrees of error protection according to the priority of the payload data in 3-D videos. An adaptive FEC code combining scheme is proposed to provide the good protection for payload data with the maximization of its code rate to minimize the extra bandwidth for FEC overhead.
Loss compensation in RF CMOS active inductor using a capacitor
(2004-12-01)
Yang, JN
;
Wu, MJ
;
Lee, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Loss compensation in a RF CMOS active inductor with using a capacitor is proposed. This simple compensation technique yields a negative conductance characteristic that can compensate for the constant internal loss of active devices. Simulation results show that the inductor obtains a maximum Q-value of 1.2E8, an inductance value in the range of 50 nH to 450 nH, and a 1.4E-6 Omega of minimum total equivalent loss in the range of 0.6 GHz to 1.3 GHz.
Segmentation of confocal microscopic image of insect brain
(2002)
Wu, MJ
;
Lin, CY
;
Ching, YT
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資訊工程學系
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Department of Computer Science
Accurate analysis of insect brain structures in digital confocal microscopic images is valuable and important to biology research needs. The first step is to segment meaningful structures from images. Active contour model, known as snakes, is widely used for segmentation of medical images. A new class of active contour model called gradient vector flow snake has been introduced in 1998 to overcome some critical problems encountered in the traditional snake. In this paper, we use gradient vector flow snake to segment the mushroom body and the central body from the confocal microscopic insect brain images. First, an edge map is created from images by some edge filters. Second, a gradient vector flow field is calculated from the edge map using a computational diffusion process. Finally, a traditional snake deformation process starts until it reaches a stable configuration. User interface is also provided here, allowing users to edit the snake during deformation process, if desired. Using the gradient vector flow snake as the main segmentation method and assist with user interface, we can properly segment the confocal microscopic insect brain image for most of the cases. The identified mushroom and central body can then be used as the preliminary results toward a 3-D reconstruction process for further biology researches.