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2004 Vol. 26, No. 5
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2004, 26(5): 673-678.
Abstract:
During wavelet image processing, the variance of Gaussian white noise is usually estimated in the finest HH subband. A popular method, proposed by Donoho and Johnstone, is often found to provide too large an estimate. To tackle this problem, this paper presents a new method. The new method takes the rude estimate from Donohos method as the starting point, and then a subband more dominated by noise is produced with the signal filtered out by a filter derived from statistics theory and a newly-proposed coefRcient model, the doubly stochastic process. Thus a finer estimate is possible by using Donohos method on the filtered HH subband. Through employing EM algorithm, the new method can he straightly extended to the case of non-Gaussian noise. Experimental results show that the new method can improve the estimate quite much when compared to Donohos method.
During wavelet image processing, the variance of Gaussian white noise is usually estimated in the finest HH subband. A popular method, proposed by Donoho and Johnstone, is often found to provide too large an estimate. To tackle this problem, this paper presents a new method. The new method takes the rude estimate from Donohos method as the starting point, and then a subband more dominated by noise is produced with the signal filtered out by a filter derived from statistics theory and a newly-proposed coefRcient model, the doubly stochastic process. Thus a finer estimate is possible by using Donohos method on the filtered HH subband. Through employing EM algorithm, the new method can he straightly extended to the case of non-Gaussian noise. Experimental results show that the new method can improve the estimate quite much when compared to Donohos method.
2004, 26(5): 679-684.
Abstract:
Image registration is an very important technology in multisensor image fusion. There is little correlation among multisensor images, especially images with different bands. It is very difficult to matching these images. Among some images which can be described in affine model, edge is a very obvious character. In this article, wavelet analysis is used to extract image edge, then correlative deviation is calculated. When correlative deviation reaches the minor, the image registration parameters are obtained. The processing of SPOT and TM images demonstrates the efficacy of the proposed method.
Image registration is an very important technology in multisensor image fusion. There is little correlation among multisensor images, especially images with different bands. It is very difficult to matching these images. Among some images which can be described in affine model, edge is a very obvious character. In this article, wavelet analysis is used to extract image edge, then correlative deviation is calculated. When correlative deviation reaches the minor, the image registration parameters are obtained. The processing of SPOT and TM images demonstrates the efficacy of the proposed method.
2004, 26(5): 685-689.
Abstract:
Based on the image halftone technique, a new effective image authentication algorithm is proposed with self repairing ability. First, the original image is quantized by 4 bit based 011 the error diffusion image halftone, and then the result is permuted by chaos operator, at the same time the halftone color set is constructed with the least quantization error. Next, the permuted image is hidden into the original image based on the error diffusion watermark algorithm. When the watermarked image is received, to verify the authenticity of the received image, the hidden information is extracted out from the received image and permuted inversely. If the received image is similar to the extracted information, the received image is creditable, else that is to say, there exists a local region that is dissimilarity, i.e. the region is tampered, according to corresponding region of extracted information, the tampered region is repaired. Finally, experimental result to demonstrate the effectiveness of the proposed image authentication technique is presented.
Based on the image halftone technique, a new effective image authentication algorithm is proposed with self repairing ability. First, the original image is quantized by 4 bit based 011 the error diffusion image halftone, and then the result is permuted by chaos operator, at the same time the halftone color set is constructed with the least quantization error. Next, the permuted image is hidden into the original image based on the error diffusion watermark algorithm. When the watermarked image is received, to verify the authenticity of the received image, the hidden information is extracted out from the received image and permuted inversely. If the received image is similar to the extracted information, the received image is creditable, else that is to say, there exists a local region that is dissimilarity, i.e. the region is tampered, according to corresponding region of extracted information, the tampered region is repaired. Finally, experimental result to demonstrate the effectiveness of the proposed image authentication technique is presented.
2004, 26(5): 690-695.
Abstract:
Basic principals of digital quadrature coherent detection are described in this paper via interpolation method. Two implementations are presented, and the signal flow is analysed. The rejection effects to mirror frequencies are discussed and compared emphatically between the two implementations. Computer simulation is carried out. Both the theoretical analysis and simulation results make a good reference to engineering application.
Basic principals of digital quadrature coherent detection are described in this paper via interpolation method. Two implementations are presented, and the signal flow is analysed. The rejection effects to mirror frequencies are discussed and compared emphatically between the two implementations. Computer simulation is carried out. Both the theoretical analysis and simulation results make a good reference to engineering application.
2004, 26(5): 696-701.
Abstract:
Detecting singularities of multi-dimensional signals is important and interesting in various fields. The edge of an image and the directions of singularity can be regarded as a wavefront set in the meaning of microlocal analysis, which is intuitively illustrated from the viewpoint of engineering in this paper. A wavefront detection algorithm is proposed, which is based on microlocal analysis and can be applied to image analysis, multi-dimensional signal detection and many other related fields. Experimental results indicate that this algorithm is simple and successful.
Detecting singularities of multi-dimensional signals is important and interesting in various fields. The edge of an image and the directions of singularity can be regarded as a wavefront set in the meaning of microlocal analysis, which is intuitively illustrated from the viewpoint of engineering in this paper. A wavefront detection algorithm is proposed, which is based on microlocal analysis and can be applied to image analysis, multi-dimensional signal detection and many other related fields. Experimental results indicate that this algorithm is simple and successful.
2004, 26(5): 702-708.
Abstract:
A novel blind deconvolution algorithm based on autocorrelation function of band-pass signal is proposed, only single input is required. The input data is transformed to its complex baseband through demodulation and decimation processing. For the baseband signal, a blind deconvolution algorithm is deduced, which minimizes the squared sum of the real part of the signal autocorrelation function over a region excluding a region near the zero delay point. Computer simulations show that the algorithm works well. It is widely applicable for bandpass Gaussian as well as non-Gaussian signals.
A novel blind deconvolution algorithm based on autocorrelation function of band-pass signal is proposed, only single input is required. The input data is transformed to its complex baseband through demodulation and decimation processing. For the baseband signal, a blind deconvolution algorithm is deduced, which minimizes the squared sum of the real part of the signal autocorrelation function over a region excluding a region near the zero delay point. Computer simulations show that the algorithm works well. It is widely applicable for bandpass Gaussian as well as non-Gaussian signals.
2004, 26(5): 709-714.
Abstract:
Time-Frequency parameter estimation and direction finding for nonstationary signals impinging on an antenna array over a wide frequency band (2~18GHz) is under in-vestigation, and a new method for parameter and 2-D Angle-Of-Arrival (AOA) estimation of spatio-temporal undersampled LFM sources is proposed in this paper. The proposed method uses time domain dechirp algorithm for chirp rates estimation. By filtering in the fractional Fourier domain, signals are extracted from the mixture of sources and noise. Un-ambiguous initial frequency estimates are obtained from the output of the reference element and its time delayed version, while 2-D AOA estimation is based on the array model in FRFT beamspace. Numerical simulations show that this method can deal with multiple LFM sources. Parameter and AOA estimation with high accuracy is available at low SNR.
Time-Frequency parameter estimation and direction finding for nonstationary signals impinging on an antenna array over a wide frequency band (2~18GHz) is under in-vestigation, and a new method for parameter and 2-D Angle-Of-Arrival (AOA) estimation of spatio-temporal undersampled LFM sources is proposed in this paper. The proposed method uses time domain dechirp algorithm for chirp rates estimation. By filtering in the fractional Fourier domain, signals are extracted from the mixture of sources and noise. Un-ambiguous initial frequency estimates are obtained from the output of the reference element and its time delayed version, while 2-D AOA estimation is based on the array model in FRFT beamspace. Numerical simulations show that this method can deal with multiple LFM sources. Parameter and AOA estimation with high accuracy is available at low SNR.
2004, 26(5): 715-721.
Abstract:
It is one of the key technologies to MPEG-4 grade codes based on target to segment and track the concerned video objects from the video scene. Most current seg-mentation and tracking algorithms are of high complexity but not effective in getting rid of background noise. One algorithm is put forward to segment and trace video objects based on edge difference among multiple frames. According to the proposed algorithm, edge difference between a group of frames is used to draw the area of moving objects; then, background pixels are removed through setting up pixel-measuring window and threshold value; the area of objects is set up by morphology operator; at the same time, vectors between the last concerned objects per frame and moving objects of present frame are established to follow current concerned objects. The result of various standard video test sequences shows that the proposed algorithm offers more accurate, faster and more effective segmentation and tracking of concerned video moving objects.
It is one of the key technologies to MPEG-4 grade codes based on target to segment and track the concerned video objects from the video scene. Most current seg-mentation and tracking algorithms are of high complexity but not effective in getting rid of background noise. One algorithm is put forward to segment and trace video objects based on edge difference among multiple frames. According to the proposed algorithm, edge difference between a group of frames is used to draw the area of moving objects; then, background pixels are removed through setting up pixel-measuring window and threshold value; the area of objects is set up by morphology operator; at the same time, vectors between the last concerned objects per frame and moving objects of present frame are established to follow current concerned objects. The result of various standard video test sequences shows that the proposed algorithm offers more accurate, faster and more effective segmentation and tracking of concerned video moving objects.
2004, 26(5): 722-726.
Abstract:
This paper presents a HMM Local Optimal state Path-based Data Imputation (LOPDI) algorithm. Speech feature vector sequences are presumed to be the outputs of an L state HMM. The HMM state sequence is estimated by local optimal path procedure. Then, missing data is recovered by MAP procedure. Experimental result shows that LOPDI algorithm can greatly increase automatic speech recognition systems robustness against additive noise.
This paper presents a HMM Local Optimal state Path-based Data Imputation (LOPDI) algorithm. Speech feature vector sequences are presumed to be the outputs of an L state HMM. The HMM state sequence is estimated by local optimal path procedure. Then, missing data is recovered by MAP procedure. Experimental result shows that LOPDI algorithm can greatly increase automatic speech recognition systems robustness against additive noise.
2004, 26(5): 727-732.
Abstract:
For processing the data of squint mode SAR, the modified subaperture approach based on classical real-time subaperture processing is presented in this paper. This new ap-proach can improve the image quality obviously and make the auto-focus processing converge better. At the same time, a new clutterlock algorithm of proportion factor self-adaptive in image field is introduced, which can improve the converging speed and the precision of result. In this paper, the memory requirements in the real-time processing procedures are discussed carefully. Finally, the amount of computing is analyzed and compared with that of the R-D algorithm.
For processing the data of squint mode SAR, the modified subaperture approach based on classical real-time subaperture processing is presented in this paper. This new ap-proach can improve the image quality obviously and make the auto-focus processing converge better. At the same time, a new clutterlock algorithm of proportion factor self-adaptive in image field is introduced, which can improve the converging speed and the precision of result. In this paper, the memory requirements in the real-time processing procedures are discussed carefully. Finally, the amount of computing is analyzed and compared with that of the R-D algorithm.
2004, 26(5): 733-738.
Abstract:
Based on the study on the features and characteristics of random Radio Frequency Interference (RFI) in impulse radar, this paper firstly analyzes the RFI supperession in Ultra Wide Band(UWB) time domain receivers. Taking Mean Square Error (MSE) as principle, the wave-average filtering and the median filtering methods of random RFI suppression are raised. The performance of the two methods is demonstrated on data collected from impulse radar and the experimental results also show their consistence.
Based on the study on the features and characteristics of random Radio Frequency Interference (RFI) in impulse radar, this paper firstly analyzes the RFI supperession in Ultra Wide Band(UWB) time domain receivers. Taking Mean Square Error (MSE) as principle, the wave-average filtering and the median filtering methods of random RFI suppression are raised. The performance of the two methods is demonstrated on data collected from impulse radar and the experimental results also show their consistence.
2004, 26(5): 739-745.
Abstract:
A new imaging method is proposed for multi-aperture wide-swath Synthetic Aperture Radar (SAR) in this paper. The imaging algorithm is proved theoretically, and the weighting matrix is proved to be in good condition. The computational complexity of the imaging algorithm is analyzed. The Signal-to-Noise Ratio (SNR) of this kind of multi-aperture wide-swath SAR is discussed. Finally, the simulation result is presented.
A new imaging method is proposed for multi-aperture wide-swath Synthetic Aperture Radar (SAR) in this paper. The imaging algorithm is proved theoretically, and the weighting matrix is proved to be in good condition. The computational complexity of the imaging algorithm is analyzed. The Signal-to-Noise Ratio (SNR) of this kind of multi-aperture wide-swath SAR is discussed. Finally, the simulation result is presented.
2004, 26(5): 746-751.
Abstract:
The needed interpolation of keystone transformation used for every subaperture is the bottleneck of imaging for lower frequency Synthetic Aperture Radar(SAR) especially for Ultra Wide Band(UWB) SAR with Planar Sub Aperture Processing(PSAP). A new in-terpolation method for keystone transformation is presented in this paper, and by mending the algorithm, the redundant computation of its realization is eliminated, the efficiency of the algorithm is improved notably. The computer simulation and the real data test results show that the modified PSAP can be applied to real-time UWB-SAR imaging of wide scene with fine resolution.
The needed interpolation of keystone transformation used for every subaperture is the bottleneck of imaging for lower frequency Synthetic Aperture Radar(SAR) especially for Ultra Wide Band(UWB) SAR with Planar Sub Aperture Processing(PSAP). A new in-terpolation method for keystone transformation is presented in this paper, and by mending the algorithm, the redundant computation of its realization is eliminated, the efficiency of the algorithm is improved notably. The computer simulation and the real data test results show that the modified PSAP can be applied to real-time UWB-SAR imaging of wide scene with fine resolution.
2004, 26(5): 752-759.
Abstract:
In this paper, an unsupervised Wishart classification scheme for polarimetric interferometric SAR data sets is introduced. A 6x6 polarimetric interferometric coherency matrix is used, in order to take simultaneously into account the full polarimetric information from one single image and the coherency information between the pair of these images. This classification scheme is applied to full polarimetric interferometric L-band SAR image pairs of Tien Shan, China, acquired by the NASA/JPL SIR-C/X-SAR sensor in 1994. The results show that this scheme can identify different terrain types and at the same time keep thr details of surface features, which improve greatly the results of the polarimetric unsupervised Wishart classification.
In this paper, an unsupervised Wishart classification scheme for polarimetric interferometric SAR data sets is introduced. A 6x6 polarimetric interferometric coherency matrix is used, in order to take simultaneously into account the full polarimetric information from one single image and the coherency information between the pair of these images. This classification scheme is applied to full polarimetric interferometric L-band SAR image pairs of Tien Shan, China, acquired by the NASA/JPL SIR-C/X-SAR sensor in 1994. The results show that this scheme can identify different terrain types and at the same time keep thr details of surface features, which improve greatly the results of the polarimetric unsupervised Wishart classification.
2004, 26(5): 760-765.
Abstract:
Ordered Successive Interference Cancellation (OSIC), the conventional detec-tion algorithm for VBLAST, decreases the complexity, comparing with the Maximum Like-lihood (ML), but its performance is much worse than that of ML. In this paper, Partial Decision OSIC (PD_OSIC), a modified detection algorithm is presented for VBLAST. It in-creases the number of candidate decision symbols and uses ML detection in the last layer, so it improves the detection performance. The simulation results show that the algorithm proposed gets far better performance than OSIC.
Ordered Successive Interference Cancellation (OSIC), the conventional detec-tion algorithm for VBLAST, decreases the complexity, comparing with the Maximum Like-lihood (ML), but its performance is much worse than that of ML. In this paper, Partial Decision OSIC (PD_OSIC), a modified detection algorithm is presented for VBLAST. It in-creases the number of candidate decision symbols and uses ML detection in the last layer, so it improves the detection performance. The simulation results show that the algorithm proposed gets far better performance than OSIC.
2004, 26(5): 766-770.
Abstract:
In this paper, the effect of packet duration and channel prediction is analyzed in adaptive modulation. Spectral efficiency equations are derived for both systems with and without channel prediction. Numerical results show that systems with channel prediction can get maximum spectral efficiency while systems without channel prediction but chosen optimum packet length can get suboptimum frequency efficiency, which is inversely proportional to Doppler frequency.
In this paper, the effect of packet duration and channel prediction is analyzed in adaptive modulation. Spectral efficiency equations are derived for both systems with and without channel prediction. Numerical results show that systems with channel prediction can get maximum spectral efficiency while systems without channel prediction but chosen optimum packet length can get suboptimum frequency efficiency, which is inversely proportional to Doppler frequency.
2004, 26(5): 771-776.
Abstract:
A motion compensated adaptive frame interpolation technique based on mesh model is proposed considering occlusion issue existed in two-dimensional motion estimation. The whole image is divided into three types of regions in order to perform motion estimation and motion compensated frame interpolation respectively. A more accurate occlusion detec-tion method is presented to improve the precision of detection, which is the main premise of the adaptive interpolation. The motion estimation error introduced by occlusion regions is reduced effectively. Mesh node motion estimation based on feature window matching is used to achieve sub-pixel resolution and overcome block artifacts produced by block matching. Experimental results indicate that the proposed algorithm is easy to implement, and solves motion estimation problem existed in occlusion regions effectively. The interpolated image shows better visual performance.
A motion compensated adaptive frame interpolation technique based on mesh model is proposed considering occlusion issue existed in two-dimensional motion estimation. The whole image is divided into three types of regions in order to perform motion estimation and motion compensated frame interpolation respectively. A more accurate occlusion detec-tion method is presented to improve the precision of detection, which is the main premise of the adaptive interpolation. The motion estimation error introduced by occlusion regions is reduced effectively. Mesh node motion estimation based on feature window matching is used to achieve sub-pixel resolution and overcome block artifacts produced by block matching. Experimental results indicate that the proposed algorithm is easy to implement, and solves motion estimation problem existed in occlusion regions effectively. The interpolated image shows better visual performance.
2004, 26(5): 777-782.
Abstract:
In this paper, a wireless fair scheduling algorithm is proposed using proportional compensation mode. It can distinguish the services in different application levels and use different queueing strategies for each class of services. A compensation strategy and a reallocation method in the algorithm are introduced to achieve wireless fair services. The compensation that the lagging flow can get is proportion to the lagging flows original transport speed.
In this paper, a wireless fair scheduling algorithm is proposed using proportional compensation mode. It can distinguish the services in different application levels and use different queueing strategies for each class of services. A compensation strategy and a reallocation method in the algorithm are introduced to achieve wireless fair services. The compensation that the lagging flow can get is proportion to the lagging flows original transport speed.
2004, 26(5): 783-788.
Abstract:
Blind fractionally spaced equalizers can reduce intersymbol interference using only second-order statistics. A blind MMSE equalizer based on linear prediction is presented in this paper. It can directly equalize the channel from the fractionally sampled observations without performing channel identification. In addition, it can be implemented efficiently using the RLS algorithm. Simulation results show that the blind MMSE equalizer has smaller mean-square error of symbol estimation than the corresponding zero-forcing equalizer.
Blind fractionally spaced equalizers can reduce intersymbol interference using only second-order statistics. A blind MMSE equalizer based on linear prediction is presented in this paper. It can directly equalize the channel from the fractionally sampled observations without performing channel identification. In addition, it can be implemented efficiently using the RLS algorithm. Simulation results show that the blind MMSE equalizer has smaller mean-square error of symbol estimation than the corresponding zero-forcing equalizer.
2004, 26(5): 789-794.
Abstract:
Because of its scalability, the idea of coarse packet classification can be uti-lized to OBS network. However, due to the limited priorities supported by OBS networks, multi-class burst assembly technique is usually adopted. Hence, a novel map algorithm, i.e. TQ-map, is proposed, which can determine which classes of packets a priority burst can contain, and fit for the multi-class burst assembly. Its most important feature is adaptivity. Compared with S-map, TQ-Map can establish the map relations varying with both traffic condition and QoS requirement, and moreover allocates the burst assembling capacity be-tween packets classes fairly, efficiently and differentially. The only one purpose is to match the QoS requirements of high layers applications. The simulation results show that TQ-Map can effectively achieve the purpose to support QoS.
Because of its scalability, the idea of coarse packet classification can be uti-lized to OBS network. However, due to the limited priorities supported by OBS networks, multi-class burst assembly technique is usually adopted. Hence, a novel map algorithm, i.e. TQ-map, is proposed, which can determine which classes of packets a priority burst can contain, and fit for the multi-class burst assembly. Its most important feature is adaptivity. Compared with S-map, TQ-Map can establish the map relations varying with both traffic condition and QoS requirement, and moreover allocates the burst assembling capacity be-tween packets classes fairly, efficiently and differentially. The only one purpose is to match the QoS requirements of high layers applications. The simulation results show that TQ-Map can effectively achieve the purpose to support QoS.
2004, 26(5): 795-799.
Abstract:
Current Internet uses typically drop tail as its buffer management scheme. This scheme does not meet the need of DiffServ model, while RED and its improved algorithms also suffer from shortcoming in term of fairness and relative drop precedence. This paper analyzes several popular packet scheduling algorithms, proposes a novel scalable algorithm named D-CHOKe(Difference-CHOKe) based on DiffServ model. This algorithm achieves fairness and relative drop precedence, and keep the scalability of the IP network. Simulation demonstrates that D-CHOKe algorithm well meets the requirements of DiffServ.
Current Internet uses typically drop tail as its buffer management scheme. This scheme does not meet the need of DiffServ model, while RED and its improved algorithms also suffer from shortcoming in term of fairness and relative drop precedence. This paper analyzes several popular packet scheduling algorithms, proposes a novel scalable algorithm named D-CHOKe(Difference-CHOKe) based on DiffServ model. This algorithm achieves fairness and relative drop precedence, and keep the scalability of the IP network. Simulation demonstrates that D-CHOKe algorithm well meets the requirements of DiffServ.
2004, 26(5): 800-806.
Abstract:
A fully differential R-MOSFET-C fourth-order Chebyshev filter employing fully differential operational amplifier, passive resistors and current-steering MOS transistors is proposed, this proposed implementation relies on the tunability of current-steering MOS transistors in the triode region acting as variable resistors in order that the cutoff frequency of the filter could be tuned continuously, the amplifier is not only with voltage common-mode negative feedback, but also with current common-mode negative feedback, which will benefit for the stability of its dc operating point, the filter whose cutoff frequency range is from 20kHz to 420kHz, demonstrates better than 65dB THD with 100kHz, 2.5Vpp input signal in Taiwan UMC 2P2M(2-Poly, 2-Metal) 0.5pm CMOS technology, the filter measures 0.36mm2, and consumes only 16mW from a single 5.0V power supply.
A fully differential R-MOSFET-C fourth-order Chebyshev filter employing fully differential operational amplifier, passive resistors and current-steering MOS transistors is proposed, this proposed implementation relies on the tunability of current-steering MOS transistors in the triode region acting as variable resistors in order that the cutoff frequency of the filter could be tuned continuously, the amplifier is not only with voltage common-mode negative feedback, but also with current common-mode negative feedback, which will benefit for the stability of its dc operating point, the filter whose cutoff frequency range is from 20kHz to 420kHz, demonstrates better than 65dB THD with 100kHz, 2.5Vpp input signal in Taiwan UMC 2P2M(2-Poly, 2-Metal) 0.5pm CMOS technology, the filter measures 0.36mm2, and consumes only 16mW from a single 5.0V power supply.
2004, 26(5): 807-812.
Abstract:
In this paper, by supposing the currents on the two lines are equal but opposite and with the application of bifilar transmission-line theory, the current-voltage relationships of the asymmetrical (current) bifilar even transmission line are obtained. It also gives a useful and effective analysis method for bifilar transmission-line transformer. The calculated values are in good agreement with the metrical values.
In this paper, by supposing the currents on the two lines are equal but opposite and with the application of bifilar transmission-line theory, the current-voltage relationships of the asymmetrical (current) bifilar even transmission line are obtained. It also gives a useful and effective analysis method for bifilar transmission-line transformer. The calculated values are in good agreement with the metrical values.
2004, 26(5): 813-819.
Abstract:
A broadband output circuit with a workable relative bandwidth bigger than 14% for L-band multiple beam klystron, in which a 7r-mode strong coupling double-gap output cavity is loaded with a coaxial filter, is designed, analyzed and calculated in detail in this paper. The research results show that the broadband output circuit with a coaxial filter not only can be used in lower frequency broadband klystron, but also has a wider output band, a much smaller volume and a much lesser weight. These characteristics will be beneficial greatly to the diminution of lower frequency broadband klystrons.
A broadband output circuit with a workable relative bandwidth bigger than 14% for L-band multiple beam klystron, in which a 7r-mode strong coupling double-gap output cavity is loaded with a coaxial filter, is designed, analyzed and calculated in detail in this paper. The research results show that the broadband output circuit with a coaxial filter not only can be used in lower frequency broadband klystron, but also has a wider output band, a much smaller volume and a much lesser weight. These characteristics will be beneficial greatly to the diminution of lower frequency broadband klystrons.
2004, 26(5): 820-824.
Abstract:
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2004, 26(5): 825-829.
Abstract:
EMD (Empirical Mode Decomposition) method is a self-adaptive signal decomposition approach. On the basis of the characteristics of the gear fault vibration signals, EMD is applied to gear fault diagnosis. The result of the application indicates that the characteristics of gear fault vibration signals can be extracted by EMD method efficiently.
EMD (Empirical Mode Decomposition) method is a self-adaptive signal decomposition approach. On the basis of the characteristics of the gear fault vibration signals, EMD is applied to gear fault diagnosis. The result of the application indicates that the characteristics of gear fault vibration signals can be extracted by EMD method efficiently.
2004, 26(5): 830-834.
Abstract:
OGY method(1990) is applied to control the chaos exhibited by current-mode controlled boost dc-dc converter, as its chaotic regime has been established in this paper. This is achieved by using discrete-time model and making simplification of the control loop design. Both simulation and experiment are done. Stability of the circuit is obtained, which proves this control method is valid in controlling switching circuit.
OGY method(1990) is applied to control the chaos exhibited by current-mode controlled boost dc-dc converter, as its chaotic regime has been established in this paper. This is achieved by using discrete-time model and making simplification of the control loop design. Both simulation and experiment are done. Stability of the circuit is obtained, which proves this control method is valid in controlling switching circuit.
2004, 26(5): 835-840.
Abstract:
The simulation calculation with the computer using FORTRAN language for frequency characteristics of the microwave duplexer tube (TR tube) is described in this pa-per. It is based on the theory of microwave four terminal networks with lumped parameter elements. The theoretical equations expressing the frequency charcteristics of TR. tube is given firstly. Then the effects of some factors, such as the staggered tuning, the length of coupling transmission line, and the element loss on the frequency characteristics are calcu-lated and discussed. The optimum values of staggered timing and optimum length of the line of a iour-resonate-elemeiit TR tube are given, and compared with the experimental data. In the program, the optimum parameters of the TR tube can be chosen automatically, and the curve of frequency characteristics is directly shown in the screen. The calculating model and method are also suitable for conventional microwave filter.
The simulation calculation with the computer using FORTRAN language for frequency characteristics of the microwave duplexer tube (TR tube) is described in this pa-per. It is based on the theory of microwave four terminal networks with lumped parameter elements. The theoretical equations expressing the frequency charcteristics of TR. tube is given firstly. Then the effects of some factors, such as the staggered tuning, the length of coupling transmission line, and the element loss on the frequency characteristics are calcu-lated and discussed. The optimum values of staggered timing and optimum length of the line of a iour-resonate-elemeiit TR tube are given, and compared with the experimental data. In the program, the optimum parameters of the TR tube can be chosen automatically, and the curve of frequency characteristics is directly shown in the screen. The calculating model and method are also suitable for conventional microwave filter.
