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2001 Vol. 23, No. 2
Display Method:
2001, 23(2): 105-111.
Abstract:
The VPN service management architecture is proposed based on the logical layer architecture of the TMN and the function of the subsystem in the architecture is analyzed. Based on this, the management information modei of the VPN service management is presented and the mapping relationship between this modei and ATM network/network element layer managed object classes is also given. The security function of the system is discussed in detail.
The VPN service management architecture is proposed based on the logical layer architecture of the TMN and the function of the subsystem in the architecture is analyzed. Based on this, the management information modei of the VPN service management is presented and the mapping relationship between this modei and ATM network/network element layer managed object classes is also given. The security function of the system is discussed in detail.
2001, 23(2): 112-117.
Abstract:
In this paper, the clock-controlled sequence is presented as a potentially superior spreading code for A-CDMA systems. First, on the basis of an A-CDMA system modei, the relationship between the average bit error probability and the cross-correlation parameters of the PN (Pseudo Noise) sequences is established. The conditions, which the PN sequences as spreading codes should satisfy, are derived from the above relationship. Next, the feasibility of the clock-controlled sequences as the spreading codes for an A-CDMA system are analyzed systematically. Finally, the cross-correlation functions between m-sequence and clock-controlled sequence, as well as the average bit error probability (BEP) corresponding to both sequences under various user number, are compared in numerical results. The feasibility of the clock- controlled sequences as spreading codes is thus verified when U75.
In this paper, the clock-controlled sequence is presented as a potentially superior spreading code for A-CDMA systems. First, on the basis of an A-CDMA system modei, the relationship between the average bit error probability and the cross-correlation parameters of the PN (Pseudo Noise) sequences is established. The conditions, which the PN sequences as spreading codes should satisfy, are derived from the above relationship. Next, the feasibility of the clock-controlled sequences as the spreading codes for an A-CDMA system are analyzed systematically. Finally, the cross-correlation functions between m-sequence and clock-controlled sequence, as well as the average bit error probability (BEP) corresponding to both sequences under various user number, are compared in numerical results. The feasibility of the clock- controlled sequences as spreading codes is thus verified when U75.
2001, 23(2): 118-124.
Abstract:
This paper discussed the uniform under-sampling of multiple bandpass signals in digital receiver. For these multiple real or complex bandpass signals having arbitrary band position and bandwidth, the acceptable sampling rate has been given. Using this sampling rate to sample the input bandpass signal, an efficient data compression can be gotten. In the same time using band pass filter, these multiple bandpass signals can be transferred to the lower frequency. Finally, an example is given to show the correctness of the uniform sampling method of multiple bandpass signals.
This paper discussed the uniform under-sampling of multiple bandpass signals in digital receiver. For these multiple real or complex bandpass signals having arbitrary band position and bandwidth, the acceptable sampling rate has been given. Using this sampling rate to sample the input bandpass signal, an efficient data compression can be gotten. In the same time using band pass filter, these multiple bandpass signals can be transferred to the lower frequency. Finally, an example is given to show the correctness of the uniform sampling method of multiple bandpass signals.
2001, 23(2): 125-133.
Abstract:
This paper presents an algorithm for video signal coding based on 3D-wavelet transformation. When the frame order t of the video signal is replaced by order z,the video signal can be looked as a block in the 3D-space. After split the block into smaller sub-blocks,imitate the method of 2D-wavelet transformation for image, the sub-blocks can be transformed with 3D-wavelet. Most of the video signal energy is in the transformed low-frequency bands.These bands affected the visual quality of the video signal most. After quantizing different bandswith different precision and entropy coding each band, the inter- and intra-frame redundancies of the video signal can be eliminated and the data can be compressed. The simulation experiments show that this algorithm can achieve very good result.
This paper presents an algorithm for video signal coding based on 3D-wavelet transformation. When the frame order t of the video signal is replaced by order z,the video signal can be looked as a block in the 3D-space. After split the block into smaller sub-blocks,imitate the method of 2D-wavelet transformation for image, the sub-blocks can be transformed with 3D-wavelet. Most of the video signal energy is in the transformed low-frequency bands.These bands affected the visual quality of the video signal most. After quantizing different bandswith different precision and entropy coding each band, the inter- and intra-frame redundancies of the video signal can be eliminated and the data can be compressed. The simulation experiments show that this algorithm can achieve very good result.
2001, 23(2): 134-139.
Abstract:
This paper mainly studies the edge detection of noisy images. An edge detector based on the fuzzy theory is presented. The algorithm first makes the pixels in the window as a fuzzy set, and divides two sub-sets by their membership functions, and then iterates in the two sub-sets, lastly detects the edge by the difference of the two values from the two sub-sets. The computer simulation shows that the edge detector is good for attenuation not only of Gaussian noise but also of impulse noise and mixture noise.
This paper mainly studies the edge detection of noisy images. An edge detector based on the fuzzy theory is presented. The algorithm first makes the pixels in the window as a fuzzy set, and divides two sub-sets by their membership functions, and then iterates in the two sub-sets, lastly detects the edge by the difference of the two values from the two sub-sets. The computer simulation shows that the edge detector is good for attenuation not only of Gaussian noise but also of impulse noise and mixture noise.
2001, 23(2): 140-146.
Abstract:
In this paper,A new cumulants-based method for the joint estimations of frequencies and 2D-DOAs of spatial signals are dicussed. After analysing the model of data and the virtual-ESPRIT,the authors use PRO-ESPRIT to estimate the parameters of signals based on VESPA.This method utilized the capability of cumulant of aperture extension and insensitivity to additive colored Gaussian noise.M-i signals can be processed by this method with M sensors without searching procedure. The simulations demonstrate the effectiveness of the method.
In this paper,A new cumulants-based method for the joint estimations of frequencies and 2D-DOAs of spatial signals are dicussed. After analysing the model of data and the virtual-ESPRIT,the authors use PRO-ESPRIT to estimate the parameters of signals based on VESPA.This method utilized the capability of cumulant of aperture extension and insensitivity to additive colored Gaussian noise.M-i signals can be processed by this method with M sensors without searching procedure. The simulations demonstrate the effectiveness of the method.
2001, 23(2): 147-153.
Abstract:
A real-time MPEG-2 layerl,2 audio CODEC realized on one TMS320C31 chip,which is a new DSP product of TI,is developed in this paper. In order to realize code decode in real-time,new fast algorithms for MPEG-2 audio sub-band analysis filter and sub-band synthesis filter are presented respectively. Using these fast algorithms,the computational load of sub-band analysis/synthesis can be reduced to 1/5 and 1/10 that of the original algorithms respectively.All the algorithms have been simulated on software and hardware. Through a simulator,the programms are loaded to a TMS320C31 and realize code and decode in realtime.
A real-time MPEG-2 layerl,2 audio CODEC realized on one TMS320C31 chip,which is a new DSP product of TI,is developed in this paper. In order to realize code decode in real-time,new fast algorithms for MPEG-2 audio sub-band analysis filter and sub-band synthesis filter are presented respectively. Using these fast algorithms,the computational load of sub-band analysis/synthesis can be reduced to 1/5 and 1/10 that of the original algorithms respectively.All the algorithms have been simulated on software and hardware. Through a simulator,the programms are loaded to a TMS320C31 and realize code and decode in realtime.
2001, 23(2): 154-159.
Abstract:
Epipolar geometry and projective geometry between uncalibrated images in stereo vision system is analyzed and a geometrical method for projective reconstruction of stereo vision is presented after proving the relationship between the plane projective coordinates and stereo projective coordinates. The accurate nonlinear algorithm is adopted to compute the homography and projective coordinates . Experimental results demonstrate a high degree of accuracy of 3D reconstruction.
Epipolar geometry and projective geometry between uncalibrated images in stereo vision system is analyzed and a geometrical method for projective reconstruction of stereo vision is presented after proving the relationship between the plane projective coordinates and stereo projective coordinates. The accurate nonlinear algorithm is adopted to compute the homography and projective coordinates . Experimental results demonstrate a high degree of accuracy of 3D reconstruction.
2001, 23(2): 160-167.
Abstract:
A 54 parameter high-order 3-D edge-element approach based on full magnetic vector variational formulas is discussed.This approach eliminates the spurious solutions efficiently and possesses very high accuracy.The analyses of the scattering characteristics of some 3-D discontinuity problems in guided wave structures verify the effective and reliability of the present method.The comparison between the numerical results obtained with 54 and 12 parameter edge element methods shows that the present approach is more accurate and efficient.
A 54 parameter high-order 3-D edge-element approach based on full magnetic vector variational formulas is discussed.This approach eliminates the spurious solutions efficiently and possesses very high accuracy.The analyses of the scattering characteristics of some 3-D discontinuity problems in guided wave structures verify the effective and reliability of the present method.The comparison between the numerical results obtained with 54 and 12 parameter edge element methods shows that the present approach is more accurate and efficient.
2001, 23(2): 168-174.
Abstract:
This paper deals with the electromagnetic characterization of the transmission and scattering properties of a slit in a conducting plate for TM polarization. To alleviate computational constraints for the problem, a connection algorithm is developed based on microwave network theory.In this paper,the slit can be divided into sections and the generalized admittance matrix of each section can be computed by the boundary integral method. Using the connection algorithm,the aperture admittance matrix of the slit can be derived by cascading the admittance matrices of individual sections. Once the slit aperture admittance matrix is obtained,equivalent magnetic currents,the backscattered field, and the transmission coefficient are found by the generalized network principle.
This paper deals with the electromagnetic characterization of the transmission and scattering properties of a slit in a conducting plate for TM polarization. To alleviate computational constraints for the problem, a connection algorithm is developed based on microwave network theory.In this paper,the slit can be divided into sections and the generalized admittance matrix of each section can be computed by the boundary integral method. Using the connection algorithm,the aperture admittance matrix of the slit can be derived by cascading the admittance matrices of individual sections. Once the slit aperture admittance matrix is obtained,equivalent magnetic currents,the backscattered field, and the transmission coefficient are found by the generalized network principle.
2001, 23(2): 175-180.
Abstract:
An asymmetric ridge waveguide slot array is a novel linear array radiating element for phased array antenna.The phased array can scan to wide angle (60)in azimuth,and can eliminate the secondary beams when the beam is scanned, which is consisted of many vertical asymmetric ridge waveguide slot linear array elements. And at the same time, the linear array can be easy to get low side-lobe. The theoretical and experimental studies for the linear array are presented in this paper. The basic theory and key technique for the linear array are performed on which systematic design procedure can be based.A constructed sixteen-slot array is tested under the far field, the results in agreement with the theory validate the theoretical analysis and the design proceduce for collinear slot array of asymmetric ridge waveguide.
An asymmetric ridge waveguide slot array is a novel linear array radiating element for phased array antenna.The phased array can scan to wide angle (60)in azimuth,and can eliminate the secondary beams when the beam is scanned, which is consisted of many vertical asymmetric ridge waveguide slot linear array elements. And at the same time, the linear array can be easy to get low side-lobe. The theoretical and experimental studies for the linear array are presented in this paper. The basic theory and key technique for the linear array are performed on which systematic design procedure can be based.A constructed sixteen-slot array is tested under the far field, the results in agreement with the theory validate the theoretical analysis and the design proceduce for collinear slot array of asymmetric ridge waveguide.
2001, 23(2): 181-186.
Abstract:
Crosstalk between conductor traces on printed circuit board is one primary source of EMI in switching power supply.Field analysis is carried out to study the electric field on PCB.Simulation and measured emission map offer valuable visual aids to PCB designer,coupling index is introduced to indicate coupling level between two traces.Based on these emission maps and coupling index PCB designer can arrange critical trace in suitable location,so crosstalk problem between traces can be suppressed during PCB design stage.
Crosstalk between conductor traces on printed circuit board is one primary source of EMI in switching power supply.Field analysis is carried out to study the electric field on PCB.Simulation and measured emission map offer valuable visual aids to PCB designer,coupling index is introduced to indicate coupling level between two traces.Based on these emission maps and coupling index PCB designer can arrange critical trace in suitable location,so crosstalk problem between traces can be suppressed during PCB design stage.
2001, 23(2): 187-191.
Abstract:
This paper presents a novel circuit dynamic analysis method using FFT technique based on diakoptics. The algorithm di vides a complex dynamic circuit into some linear sub-circuits and link branches (linear and nonlinear). The linear sub-circuits is replaced with a multi-port dynamic source in any interval. The method makes it easy to analyze a complex circuit and improves the eificiency because FFT technique is applied.
This paper presents a novel circuit dynamic analysis method using FFT technique based on diakoptics. The algorithm di vides a complex dynamic circuit into some linear sub-circuits and link branches (linear and nonlinear). The linear sub-circuits is replaced with a multi-port dynamic source in any interval. The method makes it easy to analyze a complex circuit and improves the eificiency because FFT technique is applied.
2001, 23(2): 192-196.
Abstract:
A robust and efBcient method of human face fine location is presented using human facial structure and mathematical morphology. The algorithm, which is mainly used in head-and- shoulder video coding, plays a critical role to decrease human face predictive discrepancy and increase coding efficiency.
A robust and efBcient method of human face fine location is presented using human facial structure and mathematical morphology. The algorithm, which is mainly used in head-and- shoulder video coding, plays a critical role to decrease human face predictive discrepancy and increase coding efficiency.
2001, 23(2): 197-202.
Abstract:
The discrete Fourier transform (DFT) and fast Fourier transform (FFT) for com-plex conjugate-symmetric input data are studied in this paper. The DFT of a complex conjugate-symmetric sequence has the nature that its imaginary part is zero. An efflcient FFT algorithm is developed for such a sequence. It reduces the computation and storage requirements by half comparing to the traditional FFT algorithm.
The discrete Fourier transform (DFT) and fast Fourier transform (FFT) for com-plex conjugate-symmetric input data are studied in this paper. The DFT of a complex conjugate-symmetric sequence has the nature that its imaginary part is zero. An efflcient FFT algorithm is developed for such a sequence. It reduces the computation and storage requirements by half comparing to the traditional FFT algorithm.
2001, 23(2): 203-207.
Abstract:
The gate leakage current of 6H-SiC JFET in high temperature has been analyzed and simulated, The result shows that the effect of the gate leakage current on JFET will become more and more notable when the temperature is higher than 700K. Based on the analysis, a model of 6H-SiC JFET for high temperature is proposed, in which the two-level donor ionization model and Caughey-Thomas equation are included. The simulated results are in good agreement with measured data in a wide range of temperature from 300K to 773K.
The gate leakage current of 6H-SiC JFET in high temperature has been analyzed and simulated, The result shows that the effect of the gate leakage current on JFET will become more and more notable when the temperature is higher than 700K. Based on the analysis, a model of 6H-SiC JFET for high temperature is proposed, in which the two-level donor ionization model and Caughey-Thomas equation are included. The simulated results are in good agreement with measured data in a wide range of temperature from 300K to 773K.
