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2004 Vol. 26, No. 3
Display Method:
2004, 26(3): 337-343.
Abstract:
The problem of overdetermined Blind Source Separation (BSS) where there are more mixtures than sources is considered. Beginning with the Singular Value Decompo sition (SVD) of the separation matrix, a cost function is presented based on Independent Component Analysis (ICA), and then the ordinary gradient learning algorithm is developed. Secondly, resorting to the relative gradient, it is shown that the natural gradient learning algorithm for overdetermined BSS has the same form as that for usual complete BSS, which is verified by simulation results.
The problem of overdetermined Blind Source Separation (BSS) where there are more mixtures than sources is considered. Beginning with the Singular Value Decompo sition (SVD) of the separation matrix, a cost function is presented based on Independent Component Analysis (ICA), and then the ordinary gradient learning algorithm is developed. Secondly, resorting to the relative gradient, it is shown that the natural gradient learning algorithm for overdetermined BSS has the same form as that for usual complete BSS, which is verified by simulation results.
2004, 26(3): 344-349.
Abstract:
In allusion to wideband chirp signals with time-varying direction vector, this paper constructs STFD(Spatial Time-Frequency Distribution) by short WVD(Wigner-Ville Distribution). By eigenvalue decomposition to get signal subspace and noise subspace, a algorithm of DOA estimation based on time-frequency subspace projection is proposed . Through spatial smoothing, the problem of DOA estimation of signals with the same time-frequency signature is solved. This method need not focusing and interpolation, has high precision and low computation. Simulation shows the algorithm has better performance than the method of DOA estimation of wideband signals based on matrix interpolation proposed recently.
In allusion to wideband chirp signals with time-varying direction vector, this paper constructs STFD(Spatial Time-Frequency Distribution) by short WVD(Wigner-Ville Distribution). By eigenvalue decomposition to get signal subspace and noise subspace, a algorithm of DOA estimation based on time-frequency subspace projection is proposed . Through spatial smoothing, the problem of DOA estimation of signals with the same time-frequency signature is solved. This method need not focusing and interpolation, has high precision and low computation. Simulation shows the algorithm has better performance than the method of DOA estimation of wideband signals based on matrix interpolation proposed recently.
2004, 26(3): 350-356.
Abstract:
This paper presents a new fractional lower order moment-based 2-D direction finding method-robust covariation DOA matrix method in the presence of impulsive noise which can be modeled as a symmetric alpha-stable(SaS) process. The method extends signal models and application situation of original DOA matrix algorithm by exploiting the features of impulsive noise and SaS processes. The approach is robust against additive impulsive noise. It enhances universality and robustness of the algorithm, and remedies the shortcoming of the traditional subspace techniques employing both second-order and higher order moments, which cannot be applied in impulsive noise environments. The simulation results show the feasibility and effectiveness of the new algorithm.
This paper presents a new fractional lower order moment-based 2-D direction finding method-robust covariation DOA matrix method in the presence of impulsive noise which can be modeled as a symmetric alpha-stable(SaS) process. The method extends signal models and application situation of original DOA matrix algorithm by exploiting the features of impulsive noise and SaS processes. The approach is robust against additive impulsive noise. It enhances universality and robustness of the algorithm, and remedies the shortcoming of the traditional subspace techniques employing both second-order and higher order moments, which cannot be applied in impulsive noise environments. The simulation results show the feasibility and effectiveness of the new algorithm.
2004, 26(3): 357-363.
Abstract:
Allowable platform motion error allocation is an important part of system-wide allocation in SAR system. It is a necessary system design procedure to take into account error effects, error sources, and performance-limiting factors to determine more reasonable design. Based on analysis and simulation of impact of platform motion errors on SAR image quality, a method is proposed of allowable platform motion errors allocations in airborne SAR system. Firstly, according to actual imaging system and environment, simulation mode is built; and then allowable self-existent motion errors, allowable coexistent motion errors, modified allowable motion errors are in turn obtained; finally, considering some associated factor, reasonable project is decided. As the method counts in platform and image parameter values, type and direction of platform motion errors and scene size, it has both pertinence and rationality.
Allowable platform motion error allocation is an important part of system-wide allocation in SAR system. It is a necessary system design procedure to take into account error effects, error sources, and performance-limiting factors to determine more reasonable design. Based on analysis and simulation of impact of platform motion errors on SAR image quality, a method is proposed of allowable platform motion errors allocations in airborne SAR system. Firstly, according to actual imaging system and environment, simulation mode is built; and then allowable self-existent motion errors, allowable coexistent motion errors, modified allowable motion errors are in turn obtained; finally, considering some associated factor, reasonable project is decided. As the method counts in platform and image parameter values, type and direction of platform motion errors and scene size, it has both pertinence and rationality.
2004, 26(3): 364-369.
Abstract:
The principle of the quadrature coherent detector of the digital Synthetic Aperture Radar (SAR) is introduced in the paper. The imbalance of its I/Q is analyzed, and the uniform index of its imbalance is presented. For the correction of the digital SAR I/Q imbalance, the paper adopts a new method-interpolation polyphase Kaiser filter. The results show that when the stage of the polyphase Kaiser filter is 16 the ratio of sidelobe suppression is -74dB, and the relative instant frequency error is -1.18%.
The principle of the quadrature coherent detector of the digital Synthetic Aperture Radar (SAR) is introduced in the paper. The imbalance of its I/Q is analyzed, and the uniform index of its imbalance is presented. For the correction of the digital SAR I/Q imbalance, the paper adopts a new method-interpolation polyphase Kaiser filter. The results show that when the stage of the polyphase Kaiser filter is 16 the ratio of sidelobe suppression is -74dB, and the relative instant frequency error is -1.18%.
2004, 26(3): 370-374.
Abstract:
A new 3D noise analysis method is introduced on the basis of analyzing the radiometric performance and noise of optical satellite image. The imaging noise can be divided into seven parts according to temporal and horizontal, vertical dimensions. The paper analyses the content of 3D noise. Several satellite images are used to validate the method. This method provides a feasible way to evaluate the imaging quality and to evaluate the methods of improving image quality.
A new 3D noise analysis method is introduced on the basis of analyzing the radiometric performance and noise of optical satellite image. The imaging noise can be divided into seven parts according to temporal and horizontal, vertical dimensions. The paper analyses the content of 3D noise. Several satellite images are used to validate the method. This method provides a feasible way to evaluate the imaging quality and to evaluate the methods of improving image quality.
2004, 26(3): 375-381.
Abstract:
A continuous speech recognition system for a talking head is presented in this paper, which is based on the viseme (the basic speech unit in visual domain) HMMs and segments speech to mouth shape sequences with timing boundaries. The trisemes are for malized to consider the viseme contexts. Based on the 3D talking head images, the viseme similarity weight (VSW) is denned, and 166 visual questions are designed for the building of the triseme decision trees to tie the states of the trisemes with similar contexts, so that they can share the same parameters. For the system evaluation, besides the recognition rate, an image related measurement, the viseme similarity weighted accuracy accounts for the mismatches of the recognized viseme sequence with its reference, and jerky points in liprounding and VSW graphs help evaluate the smoothness of the resulting viseme image sequences. Results show that the viseme based speech recognition system gives smoother and more plausible mouth shapes.
A continuous speech recognition system for a talking head is presented in this paper, which is based on the viseme (the basic speech unit in visual domain) HMMs and segments speech to mouth shape sequences with timing boundaries. The trisemes are for malized to consider the viseme contexts. Based on the 3D talking head images, the viseme similarity weight (VSW) is denned, and 166 visual questions are designed for the building of the triseme decision trees to tie the states of the trisemes with similar contexts, so that they can share the same parameters. For the system evaluation, besides the recognition rate, an image related measurement, the viseme similarity weighted accuracy accounts for the mismatches of the recognized viseme sequence with its reference, and jerky points in liprounding and VSW graphs help evaluate the smoothness of the resulting viseme image sequences. Results show that the viseme based speech recognition system gives smoother and more plausible mouth shapes.
2004, 26(3): 382-388.
Abstract:
The new pattern recognition method of traditional Chinese medicine based on High Performance Liquid Chromatogram(HPLC) is presented. While a new self-organizing fuzzy neural network is also proposed in order to recognize the traditional Chinese medicine. This network is composed of two levels neural network: the first level is a self-organizing fuzzy neural network which has the automatic clustering structure for sub-class; the second level is supervised sub-class classification neural network. The whole network has not only the learning ability to neural network, but also the logic ability to fuzzy system based on rules, especially the automatic clustering ability to sub-class. The automatic clustering ability for sub-class has great meaning to the pattern recognition of traditional Chinese medicine because the traditional Chinese medicine will be very different under the condition of different place come from, different time picked up and different method dealt with. In addition, the whole network can also adapt to the fuzzy pattern recognition problem when the feature dimensions are not equal. It is manifested after abundant of traditional Chinese medicine samples have been used to test the networks abilities. The results show that the resistance to parallel removal, deformation and the adaptability to the medicines coming from new places are very strong, thus the goals expected are achieved.
The new pattern recognition method of traditional Chinese medicine based on High Performance Liquid Chromatogram(HPLC) is presented. While a new self-organizing fuzzy neural network is also proposed in order to recognize the traditional Chinese medicine. This network is composed of two levels neural network: the first level is a self-organizing fuzzy neural network which has the automatic clustering structure for sub-class; the second level is supervised sub-class classification neural network. The whole network has not only the learning ability to neural network, but also the logic ability to fuzzy system based on rules, especially the automatic clustering ability to sub-class. The automatic clustering ability for sub-class has great meaning to the pattern recognition of traditional Chinese medicine because the traditional Chinese medicine will be very different under the condition of different place come from, different time picked up and different method dealt with. In addition, the whole network can also adapt to the fuzzy pattern recognition problem when the feature dimensions are not equal. It is manifested after abundant of traditional Chinese medicine samples have been used to test the networks abilities. The results show that the resistance to parallel removal, deformation and the adaptability to the medicines coming from new places are very strong, thus the goals expected are achieved.
2004, 26(3): 389-393.
Abstract:
In this paper, the fractal scale is introduced as a new measure to describe natural physical surfaces. An Intercept And Linearity (IAL) method is proposed to determine the fractal scale automatically. Experiments indicate that the fractal scale, together with the fractal dimension can effectively reflect the fractal scale range of natural textures and the texture roughness within the scale range. For the purpose of classification, the fractal scales and the fractal dimensions along horizontal, vertical and diagonal directions are obtained to form a feature set with six parameters. The probabilistic neural network is used as the texture classifier. Results have shown satisfied classification of natural textures.
In this paper, the fractal scale is introduced as a new measure to describe natural physical surfaces. An Intercept And Linearity (IAL) method is proposed to determine the fractal scale automatically. Experiments indicate that the fractal scale, together with the fractal dimension can effectively reflect the fractal scale range of natural textures and the texture roughness within the scale range. For the purpose of classification, the fractal scales and the fractal dimensions along horizontal, vertical and diagonal directions are obtained to form a feature set with six parameters. The probabilistic neural network is used as the texture classifier. Results have shown satisfied classification of natural textures.
2004, 26(3): 394-397.
Abstract:
A new appproach to solve numerical integration is developsed in this paper, based on the algorithm of neural networks with triangle basis functions. The convergence theorem of the neural networks algorithm and the theorem of numerical integration solution and its inferences are presented and proved. By the examples of numerical integration the comparison is carried out with tradional methods. The results show that the numerical integration approach has the characteristics such as high precision, strong adaptablity, and the intergration of unknown fountions can be solved. Therefore, the numerical integration approach values significantly in many engineering applications, such as electronics, etc.
A new appproach to solve numerical integration is developsed in this paper, based on the algorithm of neural networks with triangle basis functions. The convergence theorem of the neural networks algorithm and the theorem of numerical integration solution and its inferences are presented and proved. By the examples of numerical integration the comparison is carried out with tradional methods. The results show that the numerical integration approach has the characteristics such as high precision, strong adaptablity, and the intergration of unknown fountions can be solved. Therefore, the numerical integration approach values significantly in many engineering applications, such as electronics, etc.
2004, 26(3): 400-404.
Abstract:
In this paper, two methods for the synthesis of the pattern of a linear array, based on Genetic Algorithm(GA), are discussed. The results of the two methods can all ap proximate the results of the Chebyshevs method. Compared with the method of Chebyshev, the two methods using GA have more flexibility and have no restriction on the frequency of the antenna. By using the second method which combines Schelkunoffs method with GA, arbitrary locations of nulls can be got in the pattern with other optimizing conditions.
In this paper, two methods for the synthesis of the pattern of a linear array, based on Genetic Algorithm(GA), are discussed. The results of the two methods can all ap proximate the results of the Chebyshevs method. Compared with the method of Chebyshev, the two methods using GA have more flexibility and have no restriction on the frequency of the antenna. By using the second method which combines Schelkunoffs method with GA, arbitrary locations of nulls can be got in the pattern with other optimizing conditions.
2004, 26(3): 405-409.
Abstract:
Considering CRT visual display unit and reconnaissance-receiving system as a communication system, this paper sets up two information source models and their corresponding information sink models of informations electromagnetic leakage from CRT visual display unit when image and text are displayed on the screen. Entropy preservation of the system is discussed combined with the concept of entropy loss rate of information source and entropy acquisition rate of information sink. A measure is put forward to ensure the information security of CRT visual display unit. The computational and experimental results show the consistance with the theoretical analysis.
Considering CRT visual display unit and reconnaissance-receiving system as a communication system, this paper sets up two information source models and their corresponding information sink models of informations electromagnetic leakage from CRT visual display unit when image and text are displayed on the screen. Entropy preservation of the system is discussed combined with the concept of entropy loss rate of information source and entropy acquisition rate of information sink. A measure is put forward to ensure the information security of CRT visual display unit. The computational and experimental results show the consistance with the theoretical analysis.
2004, 26(3): 410-415.
Abstract:
Especially for the reliability state detection of space borne EPC, infrared thermal imaging technique, a new non-contact detection method, and its detection principle and the constitution of the detection system are introduced; and then, after plenty of test by applying this detection method on the space borne EPC sample, a new effective mathematical model of the PCB reliability detection, which based on mathematical statistics and Euclidean distance discrimination means, is brought forward first time.
Especially for the reliability state detection of space borne EPC, infrared thermal imaging technique, a new non-contact detection method, and its detection principle and the constitution of the detection system are introduced; and then, after plenty of test by applying this detection method on the space borne EPC sample, a new effective mathematical model of the PCB reliability detection, which based on mathematical statistics and Euclidean distance discrimination means, is brought forward first time.
2004, 26(3): 416-420.
Abstract:
The multiple antenna Orthogonal Frequency Division Multiplexing(OFDM) system model is analyzed in this paper. Considering that Multiple-Input Multiple-Output(MIMO) channel can be separated into parallel subchannels by means of the singular value decomposition, and deep faded subcarriers may degrade the OFDM system perfor mance, the adaptive bit and power allocation for MIMO OFDM system are proposed. The analysis and simulation results show that the proposed adaptive MIMO OFDM improves bit error rate performance and spectral efficiency of the system.
The multiple antenna Orthogonal Frequency Division Multiplexing(OFDM) system model is analyzed in this paper. Considering that Multiple-Input Multiple-Output(MIMO) channel can be separated into parallel subchannels by means of the singular value decomposition, and deep faded subcarriers may degrade the OFDM system perfor mance, the adaptive bit and power allocation for MIMO OFDM system are proposed. The analysis and simulation results show that the proposed adaptive MIMO OFDM improves bit error rate performance and spectral efficiency of the system.
2004, 26(3): 421-426.
Abstract:
In this paper, the capacity of VSG-CDMA system with power control imperfections in the presence of multiplicate types of users is discussed. Admission criterion is derived according to the interference of inter cell Iin and other cell Iother, the admission criterion can be used for uniformity distribution or non-uniformity distribution of users. Formulas to calculate link failure probability and the distribution of other cells interference are also deduced.
In this paper, the capacity of VSG-CDMA system with power control imperfections in the presence of multiplicate types of users is discussed. Admission criterion is derived according to the interference of inter cell Iin and other cell Iother, the admission criterion can be used for uniformity distribution or non-uniformity distribution of users. Formulas to calculate link failure probability and the distribution of other cells interference are also deduced.
2004, 26(3): 427-434.
Abstract:
In WCDMA system, the radio resource management entity is usually imple mented in the radio network controller. However, transport format in dedicated channels can be changed frame by frame. This fast format change can be seen as a fast part of the ra dio resource control, which is fulfilled by MAC and physical layer in user equipment and node B without any need for L3 signaling. Based on this capability and class-based QoS policy, this paper proposed an algorithm for WCDMA uplink load control. The algorithm consists of iterative rate control and packet scheduling. Simulation results show that the proposed algorithm can achieve fair sharing radio resource and guarantee QoS under multi-service environments.
In WCDMA system, the radio resource management entity is usually imple mented in the radio network controller. However, transport format in dedicated channels can be changed frame by frame. This fast format change can be seen as a fast part of the ra dio resource control, which is fulfilled by MAC and physical layer in user equipment and node B without any need for L3 signaling. Based on this capability and class-based QoS policy, this paper proposed an algorithm for WCDMA uplink load control. The algorithm consists of iterative rate control and packet scheduling. Simulation results show that the proposed algorithm can achieve fair sharing radio resource and guarantee QoS under multi-service environments.
2004, 26(3): 435-439.
Abstract:
Techniques which can realize anonymity play an important role in the protection of partners’ privacy. Sign-cryption can sign and encrypt message in one logic step and has lower cost than that of "firstly sign and then encrypt". Based on the thoughts of Diffie-Hellman decision problem and anonymous signature, an unconditionally anonymous sign-cryption algorithm is given in this paper.
Techniques which can realize anonymity play an important role in the protection of partners’ privacy. Sign-cryption can sign and encrypt message in one logic step and has lower cost than that of "firstly sign and then encrypt". Based on the thoughts of Diffie-Hellman decision problem and anonymous signature, an unconditionally anonymous sign-cryption algorithm is given in this paper.
2004, 26(3): 440-445.
Abstract:
This article analyses the shortcomings of mobile IPv6 protocol in handoff process first, then puts forward an approach based on active network technology to solve the problems and enhance mobile IPv6. Network simulation proves that this approach has more merits and better performance.
This article analyses the shortcomings of mobile IPv6 protocol in handoff process first, then puts forward an approach based on active network technology to solve the problems and enhance mobile IPv6. Network simulation proves that this approach has more merits and better performance.
2004, 26(3): 446-452.
Abstract:
This paper focuses on measurement of Internet end-to-end delay, which is one of the important characteristics of Internet end-to-end packet dynamics. Measuring the end-to-end delay of Internet can be used in QoS management, SLA management, congestion control algorithm development, etc. The conventional methods to measure one-way delay rely on GPS receiver or NTP protocol to keep synchronization between senders clock and receivers clock. However, GPS receiver is not ubiquitous in price and environment and NTP protocol is low in accuracy. A new method based on linear programming, which can remove the skew and offset between two clocks, is presented. Measuring results show that the method works well in removing the factors which effect the end-to-end delay measurement.
This paper focuses on measurement of Internet end-to-end delay, which is one of the important characteristics of Internet end-to-end packet dynamics. Measuring the end-to-end delay of Internet can be used in QoS management, SLA management, congestion control algorithm development, etc. The conventional methods to measure one-way delay rely on GPS receiver or NTP protocol to keep synchronization between senders clock and receivers clock. However, GPS receiver is not ubiquitous in price and environment and NTP protocol is low in accuracy. A new method based on linear programming, which can remove the skew and offset between two clocks, is presented. Measuring results show that the method works well in removing the factors which effect the end-to-end delay measurement.
2004, 26(3): 453-458.
Abstract:
A blind short-time Fourier transform based approach for symbol timing in OFDM systems is proposed. The key of the described algorithm leans upon the periodic 2-D time-frequency spectrum structure. By searching the flat regions in the time direction of time-frequency spectrum of the received signal, ISI-free intervals are estimated, where optimum symbol start can be easily located. Simulation results show that the proposed algorithm is quite robust against low SNR environment, and outperforms time-domain cor relation based algorithms.
A blind short-time Fourier transform based approach for symbol timing in OFDM systems is proposed. The key of the described algorithm leans upon the periodic 2-D time-frequency spectrum structure. By searching the flat regions in the time direction of time-frequency spectrum of the received signal, ISI-free intervals are estimated, where optimum symbol start can be easily located. Simulation results show that the proposed algorithm is quite robust against low SNR environment, and outperforms time-domain cor relation based algorithms.
2004, 26(3): 459-465.
Abstract:
This paper proposes a new burst assembly technique for supporting QoS in Op tical Burst Switching (OBS) networks. It consists of the adaptive-threshold burst assembly algorithm and QoS-based random offset-time scheme. The algorithm fits well the multi-class burst assembly, and not only matches with IP QoS mechanism based on packet classifica tion, but also utilizes fairly and efficiently assembly capacity. The paper also provides the simulation for the performance improvement of the technique in Packet Loss Probability (PLP).
This paper proposes a new burst assembly technique for supporting QoS in Op tical Burst Switching (OBS) networks. It consists of the adaptive-threshold burst assembly algorithm and QoS-based random offset-time scheme. The algorithm fits well the multi-class burst assembly, and not only matches with IP QoS mechanism based on packet classifica tion, but also utilizes fairly and efficiently assembly capacity. The paper also provides the simulation for the performance improvement of the technique in Packet Loss Probability (PLP).
2004, 26(3): 466-472.
Abstract:
Researchers found unfairness in DifFServ network, to solve this problem, a TSW-based marker is proposed, which is called TCP-friendly Fair Packet Marking algo-rithm(TFPlV[). With this marker, proportional fair sharing of excess bandwidth among ag gregate can be achieved, and so the better fairness between TCP and UDP flows in an aggregate. The validation of this marking algorithm through simulation experimentation is made, and the simulation result is compared with some other marking algorithms, which verifies that the TFPM algorithm has better fairness than other algorithms.
Researchers found unfairness in DifFServ network, to solve this problem, a TSW-based marker is proposed, which is called TCP-friendly Fair Packet Marking algo-rithm(TFPlV[). With this marker, proportional fair sharing of excess bandwidth among ag gregate can be achieved, and so the better fairness between TCP and UDP flows in an aggregate. The validation of this marking algorithm through simulation experimentation is made, and the simulation result is compared with some other marking algorithms, which verifies that the TFPM algorithm has better fairness than other algorithms.
2004, 26(3): 473-478.
Abstract:
This paper presents a new call admission control algorithm. During call admission control period, for a particular call the algorithm admits the call with a certain probability, where the exact probability is based on the control policies decided by network management system. The idea and rules of the algorithm are explained in detail. Simulation results demonstrate the performance of the algorithm.
This paper presents a new call admission control algorithm. During call admission control period, for a particular call the algorithm admits the call with a certain probability, where the exact probability is based on the control policies decided by network management system. The idea and rules of the algorithm are explained in detail. Simulation results demonstrate the performance of the algorithm.
2004, 26(3): 479-483.
Abstract:
This paper brings forward a new approach for image shadow processing based on PCNN(Pulse Coupled Neural Network). The results of computer simulation show that by using PCNN shadow removal algorithm image shadow can be removed efficiently so that the object in the image is easy to be found. This paper expands application field of PCNN, which has biological background.
This paper brings forward a new approach for image shadow processing based on PCNN(Pulse Coupled Neural Network). The results of computer simulation show that by using PCNN shadow removal algorithm image shadow can be removed efficiently so that the object in the image is easy to be found. This paper expands application field of PCNN, which has biological background.
2004, 26(3): 484-488.
Abstract:
A method is proposed to solve the estimation of wideband non-Gaussian 2-D DOA in this paper. Coherent Signal-subspace Method(CSM) is used to focus the higher order statistics signal subspace at different frequency bins into a predefined subspace, then space-time DOA matrix method is used to estimate the 2-D DOA. The study and the simulation analysis indicate that the method is efficient in the wideband Gaussian noise environment.
A method is proposed to solve the estimation of wideband non-Gaussian 2-D DOA in this paper. Coherent Signal-subspace Method(CSM) is used to focus the higher order statistics signal subspace at different frequency bins into a predefined subspace, then space-time DOA matrix method is used to estimate the 2-D DOA. The study and the simulation analysis indicate that the method is efficient in the wideband Gaussian noise environment.
2004, 26(3): 489-494.
Abstract:
A quantizaiton method is presented to aim at the fractional saturation Synthetic Aperture Radar (SAR) raw data. Norm distribution is the basis of Block Adaptive Quantization (BAQ) algorithm. But in the application of BAQ, some trouble may encounter, one of these is fractional saturation of raw data. A compression algorithm based on the traditional BAQ algorithm is presented, which can select different ways to quantify the raw data. This algorithm reduces the error and increases the Signal to Quantization Noise Ratio (SQNR) without influence the compression ratio. Finally, a block of real SAR raw data are processed by the two algorithms and the result is compared with each other.
A quantizaiton method is presented to aim at the fractional saturation Synthetic Aperture Radar (SAR) raw data. Norm distribution is the basis of Block Adaptive Quantization (BAQ) algorithm. But in the application of BAQ, some trouble may encounter, one of these is fractional saturation of raw data. A compression algorithm based on the traditional BAQ algorithm is presented, which can select different ways to quantify the raw data. This algorithm reduces the error and increases the Signal to Quantization Noise Ratio (SQNR) without influence the compression ratio. Finally, a block of real SAR raw data are processed by the two algorithms and the result is compared with each other.
2004, 26(3): 495-499.
Abstract:
Based on the analysis of the spurious spectrum introduced by phase truncation which was made by Nicholas, the new simplified algorithm of spurious spectrum in the presence of phase truncation is presented by using the mapping mathematics and number theory. It is possible to precisely analyze the spurious spectrum location and the spurious amplitude introduced by phase truncation in practical applications.
Based on the analysis of the spurious spectrum introduced by phase truncation which was made by Nicholas, the new simplified algorithm of spurious spectrum in the presence of phase truncation is presented by using the mapping mathematics and number theory. It is possible to precisely analyze the spurious spectrum location and the spurious amplitude introduced by phase truncation in practical applications.
2004, 26(3): 500-504.
Abstract:
Edge Based Finite Element Method (EB-FEM) is combined with overlapping or nonoverlapping overrelaxation Domain Decomposition Method (DDM) and Boundary Integral Equation (BIE) for analyzing the electromagnetic (EM) scattering of electrically large open-ended cavities. The cavity is partitioned into several small subdomains. EB-FEM is applied in every subdomain. The coupling of each neighboring subdomains is realized by vector transmission condition, and the electric field distribution in the cavity is found by iteration. BIE is added on the aperture of the original cavity. Both the BIE and transmission condition are transformed into the third boundary condition. Several numerical results are presented, which demonstrate that the proposed approach is accurate and efficient for analysis of the EM scattering of open-ended cavities.
Edge Based Finite Element Method (EB-FEM) is combined with overlapping or nonoverlapping overrelaxation Domain Decomposition Method (DDM) and Boundary Integral Equation (BIE) for analyzing the electromagnetic (EM) scattering of electrically large open-ended cavities. The cavity is partitioned into several small subdomains. EB-FEM is applied in every subdomain. The coupling of each neighboring subdomains is realized by vector transmission condition, and the electric field distribution in the cavity is found by iteration. BIE is added on the aperture of the original cavity. Both the BIE and transmission condition are transformed into the third boundary condition. Several numerical results are presented, which demonstrate that the proposed approach is accurate and efficient for analysis of the EM scattering of open-ended cavities.
