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2002 Vol. 24, No. 5
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2002, 24(5): 577-583.
Abstract:
A simple ISAR range-Doppler algorithm is applicable to steadily small flying target. But for maneuvering target the assumption is not satisfied, as the Doppler frequency is time variant. Actually to obtain the cross-range resolution of dozens of centimeters for the large-scale or medium targets especial for S or L wave band, whose wave length is not short, the Migration Through Resolution Cell (MTRC) would be occurred on the both fringe of the ISAR imaging. In this paper the reason that caused migration through resolution cell is discussed, and a compensating algorithm is proposed. Simulation data and real data prove that this method is effective.
A simple ISAR range-Doppler algorithm is applicable to steadily small flying target. But for maneuvering target the assumption is not satisfied, as the Doppler frequency is time variant. Actually to obtain the cross-range resolution of dozens of centimeters for the large-scale or medium targets especial for S or L wave band, whose wave length is not short, the Migration Through Resolution Cell (MTRC) would be occurred on the both fringe of the ISAR imaging. In this paper the reason that caused migration through resolution cell is discussed, and a compensating algorithm is proposed. Simulation data and real data prove that this method is effective.
2002, 24(5): 584-590.
Abstract:
Terrain slope information may be drawn from polarimetric synthetic aperture radar (SAR) two-dimensional image, so that three-dimensional image can be generated. The image data to algorithm discussed in the paper is a key technique to process polarimetric SAR image data to extract terrain slope. The solution fuzzy algorithm of the polarimetric ellipse rotation angle has been proffered and proved in the paper. The target scatter cross-section or signature-peak in the co-polarization signature generates effect of drawing true terrain slope information. Finally, the paper shows the polarimetric SAR three dimensional images from authentic data.
Terrain slope information may be drawn from polarimetric synthetic aperture radar (SAR) two-dimensional image, so that three-dimensional image can be generated. The image data to algorithm discussed in the paper is a key technique to process polarimetric SAR image data to extract terrain slope. The solution fuzzy algorithm of the polarimetric ellipse rotation angle has been proffered and proved in the paper. The target scatter cross-section or signature-peak in the co-polarization signature generates effect of drawing true terrain slope information. Finally, the paper shows the polarimetric SAR three dimensional images from authentic data.
2002, 24(5): 591-596.
Abstract:
An ocean echo signal simulation system for verification and calibration of FMICW high frequency ground wave radar is presented in this paper. It is based on the principle of FMICW radar and inversion of Bragg-Doppler(B-D) spectrum. The ocean echo signals are simulated with the digital synthesis techniques. They are used for calibration of the sea-state ocean radar. The system has been tested on an FMICW radar system, the surveillance results are favorably anticipated.
An ocean echo signal simulation system for verification and calibration of FMICW high frequency ground wave radar is presented in this paper. It is based on the principle of FMICW radar and inversion of Bragg-Doppler(B-D) spectrum. The ocean echo signals are simulated with the digital synthesis techniques. They are used for calibration of the sea-state ocean radar. The system has been tested on an FMICW radar system, the surveillance results are favorably anticipated.
2002, 24(5): 597-603.
Abstract:
Speckle reduction is the primary problem of SAR (Synthetic Aperture Radar) and polarimetric SAR imagery post-processing. Because the optimal polarimetric coherent speckle filtering-Polarimetric Whitening Filtering (PWF) has the drawback of only outputting a intensity image, this paper improves on it and get all polarimetric channel intensity images.
Speckle reduction is the primary problem of SAR (Synthetic Aperture Radar) and polarimetric SAR imagery post-processing. Because the optimal polarimetric coherent speckle filtering-Polarimetric Whitening Filtering (PWF) has the drawback of only outputting a intensity image, this paper improves on it and get all polarimetric channel intensity images.
2002, 24(5): 604-609.
Abstract:
In this paper, an improved codeword searching algorithm is proposed on the basis of nearest-neighbor search algorithm. The new algorithm considers the sums and variances of image vectors. A vector is separated into two subvectors: the first half of the coordinates and the second half of the coordinates. Calculate the sums and variances of the vector and its two subvectors. Apply the result to a set of inequalities to eliminate the impossible codeword candidates. The simulation results show that the proposed algorithm is faster than the improved EENNS algorithm, and it also has the advantage in decreasing the computing complexity.
In this paper, an improved codeword searching algorithm is proposed on the basis of nearest-neighbor search algorithm. The new algorithm considers the sums and variances of image vectors. A vector is separated into two subvectors: the first half of the coordinates and the second half of the coordinates. Calculate the sums and variances of the vector and its two subvectors. Apply the result to a set of inequalities to eliminate the impossible codeword candidates. The simulation results show that the proposed algorithm is faster than the improved EENNS algorithm, and it also has the advantage in decreasing the computing complexity.
2002, 24(5): 610-614.
Abstract:
The distributed multisensor detection system with Order Statistic Constant False Alarm Rate (OS-CFAR) is optimized in terms of fusion rule and (k, T) parameters using Genetic Simulated Annealing Algorithms (GSAAs). A set of quasi-optimum results of a tri-sensor system under identically and unidentically detect conditions are given and analyzed, which proves that GSAAs are efficient for this optimization.
The distributed multisensor detection system with Order Statistic Constant False Alarm Rate (OS-CFAR) is optimized in terms of fusion rule and (k, T) parameters using Genetic Simulated Annealing Algorithms (GSAAs). A set of quasi-optimum results of a tri-sensor system under identically and unidentically detect conditions are given and analyzed, which proves that GSAAs are efficient for this optimization.
2002, 24(5): 615-620.
Abstract:
ODWT (Orthogonal Discrete Wavelet Transform) is translation-variant, which will depress the compression efficiency. To avoid the deficiency, by holding all the even and odd indexed subsamples in every scale, a bitree structure is formed here. From any route of the bitree the signal can be reconstructed. According to sonic given criterion, a best transform route can be determined. The simulations show that the compression performance of the best transform route is better than that of the ordinary ODWT.
ODWT (Orthogonal Discrete Wavelet Transform) is translation-variant, which will depress the compression efficiency. To avoid the deficiency, by holding all the even and odd indexed subsamples in every scale, a bitree structure is formed here. From any route of the bitree the signal can be reconstructed. According to sonic given criterion, a best transform route can be determined. The simulations show that the compression performance of the best transform route is better than that of the ordinary ODWT.
2002, 24(5): 621-625.
Abstract:
In this paper, the goal is to generalize the notions and properties of Wavelet packet to multiwavelet packet and to develop the theoretical framework of raultiwavelet packet. Moreover, the proof is given.
In this paper, the goal is to generalize the notions and properties of Wavelet packet to multiwavelet packet and to develop the theoretical framework of raultiwavelet packet. Moreover, the proof is given.
2002, 24(5): 626-630.
Abstract:
Subspace estimation plays an important role in a field of modern signal processing applications. This paper studied deeply the power iteration, then an approach based on power iteration for tracking the signal subspace is presented. The problems of rank-1 subspace tracking and DOA estimation are discussed. The simulation results support the theoretical predications.
Subspace estimation plays an important role in a field of modern signal processing applications. This paper studied deeply the power iteration, then an approach based on power iteration for tracking the signal subspace is presented. The problems of rank-1 subspace tracking and DOA estimation are discussed. The simulation results support the theoretical predications.
2002, 24(5): 631-636.
Abstract:
Basing on subspace principal, this paper provides a calibration approach for mutual coupling among sensors. The benefit of this new method is that calibration signals and unknown signals can be received simultaneously, during the course of calibration. The computer simulation results demonstrate that this approach can be used for uniformly spaced linear or circular arrays and direction-finding of coherent signals.
Basing on subspace principal, this paper provides a calibration approach for mutual coupling among sensors. The benefit of this new method is that calibration signals and unknown signals can be received simultaneously, during the course of calibration. The computer simulation results demonstrate that this approach can be used for uniformly spaced linear or circular arrays and direction-finding of coherent signals.
2002, 24(5): 637-643.
Abstract:
The uniform circular array is transformed into uniform linear array by the spatial matched filter transformation from element space to beam space. Based on the space-time matched filter output in frequency domain, the joint angle and delay estimation with uniform circular array in aperiodic spreading system is solved with DOA matrix method. The joint estimation algorithm also solved the problem, that the multipath number can not be larger than the element number in conventional spatial processing method. The theoretical analysis and computer simulations demonstrate that the method is an unbiased estimator and its estimation precision is superior to that of the sliding correlator.
The uniform circular array is transformed into uniform linear array by the spatial matched filter transformation from element space to beam space. Based on the space-time matched filter output in frequency domain, the joint angle and delay estimation with uniform circular array in aperiodic spreading system is solved with DOA matrix method. The joint estimation algorithm also solved the problem, that the multipath number can not be larger than the element number in conventional spatial processing method. The theoretical analysis and computer simulations demonstrate that the method is an unbiased estimator and its estimation precision is superior to that of the sliding correlator.
2002, 24(5): 644-648.
Abstract:
The realization of high resolution algorithm has been paid more attention in recent years. This paper gives the model of wide-band beam-space direction finding problem and studies the Root-MUSIC algorithm. The roots in the unit circle of the beam-space Root-MUSIC are divided into two parts, one is corresponding to the true direction, and the other is not related to the source direction. Sub-array model is used here to form beams to focus the root corresponding to the true direction in a reduced order polynomial. This process reduced the computation burden. Simulation results in various beams have shown that the beams with wider main-band and lower side-band have better estimation and resolution performance, and proved the effectiveness of the wide-band beam-space reduced order Root-MUSIC.
The realization of high resolution algorithm has been paid more attention in recent years. This paper gives the model of wide-band beam-space direction finding problem and studies the Root-MUSIC algorithm. The roots in the unit circle of the beam-space Root-MUSIC are divided into two parts, one is corresponding to the true direction, and the other is not related to the source direction. Sub-array model is used here to form beams to focus the root corresponding to the true direction in a reduced order polynomial. This process reduced the computation burden. Simulation results in various beams have shown that the beams with wider main-band and lower side-band have better estimation and resolution performance, and proved the effectiveness of the wide-band beam-space reduced order Root-MUSIC.
2002, 24(5): 649-655.
Abstract:
An information-theoretical model for subliminal channel is proposed. The task of distinguishing between an innocent signature r and that containing a subliminal message is interpreted as a hypothesis testing problem. The security of the channel is quantified in terms of the relative entropy. The security formula of the subliminal channels is deduced with hypothesis testing, and the perfectly secure conditions is given.
An information-theoretical model for subliminal channel is proposed. The task of distinguishing between an innocent signature r and that containing a subliminal message is interpreted as a hypothesis testing problem. The security of the channel is quantified in terms of the relative entropy. The security formula of the subliminal channels is deduced with hypothesis testing, and the perfectly secure conditions is given.
2002, 24(5): 656-660.
Abstract:
Based on time-space processing, a 2-D array extension method is introduced to investigate the virtual geometry of array and construct its pseudodata matrix. Meanwhile, an algorithm is presented for suppression of same-frequency interference. The equivalent array aperture of the methods is (m+1)2/2-1 (when m is odd) or m(m+2)/2-1 (when m is even) with m-sensors. The method and the algorithm can work under lower SNR (0dB), and the 2-D parameters can be automatically paired. Theoretical analysis and computer simulations show the effectiveness of the array extension and the algorithm.
Based on time-space processing, a 2-D array extension method is introduced to investigate the virtual geometry of array and construct its pseudodata matrix. Meanwhile, an algorithm is presented for suppression of same-frequency interference. The equivalent array aperture of the methods is (m+1)2/2-1 (when m is odd) or m(m+2)/2-1 (when m is even) with m-sensors. The method and the algorithm can work under lower SNR (0dB), and the 2-D parameters can be automatically paired. Theoretical analysis and computer simulations show the effectiveness of the array extension and the algorithm.
2002, 24(5): 661-666.
Abstract:
According to the characteristic of communication signals, a new method of feature selection is presented. In this method, the efficient and robust genetic algorithm is used to sift out qualified feature subset, under the rule of clustering level of same classifications and separating level of different classifications. With the fine structure of evidence theory, a considerable recognition ratio is obtained under a wide range of SNR environment. Finally, the effectiveness of this method is proved by computer simulation.
According to the characteristic of communication signals, a new method of feature selection is presented. In this method, the efficient and robust genetic algorithm is used to sift out qualified feature subset, under the rule of clustering level of same classifications and separating level of different classifications. With the fine structure of evidence theory, a considerable recognition ratio is obtained under a wide range of SNR environment. Finally, the effectiveness of this method is proved by computer simulation.
2002, 24(5): 667-670.
Abstract:
Because the feedforward neural network has an ability of approach to arbitrary nonlinear mapping, it can be used effectively in the modeling and controlling of nonlinear system. In order to improve the learning efficiency and stability of feedforward neural network, a fast learning algorithm for neural networks base on CGM-OC approach is presented. Compared with other learning methods such as BP method, Broyden Flecher Goldfarl Shanno method. Power method etc., simulation results show that the proposed method is an efficient and fast method.
Because the feedforward neural network has an ability of approach to arbitrary nonlinear mapping, it can be used effectively in the modeling and controlling of nonlinear system. In order to improve the learning efficiency and stability of feedforward neural network, a fast learning algorithm for neural networks base on CGM-OC approach is presented. Compared with other learning methods such as BP method, Broyden Flecher Goldfarl Shanno method. Power method etc., simulation results show that the proposed method is an efficient and fast method.
2002, 24(5): 671-677.
Abstract:
In this paper, the locally exponential stability of equilibrium point for a class of high order Hopfield type neural networks is studied by means of Lyapunov function. Some results about estimation of the attraction domain and exponential convergence rate of the network trajectories to equilibrium point of such networks are obtained.
In this paper, the locally exponential stability of equilibrium point for a class of high order Hopfield type neural networks is studied by means of Lyapunov function. Some results about estimation of the attraction domain and exponential convergence rate of the network trajectories to equilibrium point of such networks are obtained.
2002, 24(5): 678-683.
Abstract:
Various versions of 2D-RAKE receivers in CDMA systems are studied and their performances are analyzed and compared. Numerical results are given at the end of this paper.
Various versions of 2D-RAKE receivers in CDMA systems are studied and their performances are analyzed and compared. Numerical results are given at the end of this paper.
2002, 24(5): 684-690.
Abstract:
An improved LMS blind space-time multiuser detection method based on the Rosens gradient projection to realize in multipath CDMA channels is presented. Comparison with the original method, the proposed method has advantages in complexity and requirement of the system. However, the results of simulation comparison illustrate that the detection performance of the proposed multiuser space-time processing method do not deteriorate, and prove that this method has advantage over the original method in the competition of market.
An improved LMS blind space-time multiuser detection method based on the Rosens gradient projection to realize in multipath CDMA channels is presented. Comparison with the original method, the proposed method has advantages in complexity and requirement of the system. However, the results of simulation comparison illustrate that the detection performance of the proposed multiuser space-time processing method do not deteriorate, and prove that this method has advantage over the original method in the competition of market.
2002, 24(5): 691-695.
Abstract:
A method of high Speed RS decoding which is propitious to parallel implementation is presented in this paper. The method is suitable for error correcting decoding with high speed data recording system of disk array and high speed data communicating system. It is successfully used in high speed data recording system of disk array.
A method of high Speed RS decoding which is propitious to parallel implementation is presented in this paper. The method is suitable for error correcting decoding with high speed data recording system of disk array and high speed data communicating system. It is successfully used in high speed data recording system of disk array.
2002, 24(5): 696-701.
Abstract:
Video streaming requires high quality of service (QoS) guarantee of transport system, but current Internet only provides best-effort service, and is not suit for real-time transform of video data. To address the issues of meeting delay-constrained video streaming over Internet, this paper presents and end-to-end adaptive transmission approach without any modification to the Internet infrastructure. The design emphasis is on trying to obtain the best quality of video reception possible in the absence of network QoS guarantees. According to the estimation of available bandwidth and network feedback information, the video steam sender could adjust the sending rate, and then achieve the best transmission efficiency. Two kinds of streaming services have been considered in proposed protocols: stored video and live video. Simulation results show the well performance of proposed system for Internet video streaming.
Video streaming requires high quality of service (QoS) guarantee of transport system, but current Internet only provides best-effort service, and is not suit for real-time transform of video data. To address the issues of meeting delay-constrained video streaming over Internet, this paper presents and end-to-end adaptive transmission approach without any modification to the Internet infrastructure. The design emphasis is on trying to obtain the best quality of video reception possible in the absence of network QoS guarantees. According to the estimation of available bandwidth and network feedback information, the video steam sender could adjust the sending rate, and then achieve the best transmission efficiency. Two kinds of streaming services have been considered in proposed protocols: stored video and live video. Simulation results show the well performance of proposed system for Internet video streaming.
2002, 24(5): 702-706.
Abstract:
The design method is given for the digital piecewise linear mapping system based on FPGA chip. In this method, the perturbation of m-sequence is used to overcome the short period of chaotic sequence caused by the finite precision effect. The piecewise linear chaotic generator is realized by means of VHDL and the simulations are made. The balance, the correlation and the linear complexity are compared between digital chaotic sequence and analogue chaotic sequence. A road is explored to apply the piecewise linear mapping system to a practical spreading spectrum system.
The design method is given for the digital piecewise linear mapping system based on FPGA chip. In this method, the perturbation of m-sequence is used to overcome the short period of chaotic sequence caused by the finite precision effect. The piecewise linear chaotic generator is realized by means of VHDL and the simulations are made. The balance, the correlation and the linear complexity are compared between digital chaotic sequence and analogue chaotic sequence. A road is explored to apply the piecewise linear mapping system to a practical spreading spectrum system.
2002, 24(5): 707-710.
Abstract:
STAP has been widely studied for airborne radar as an approach to adaptively detect small target competing with ground clutter. Non-homogeneous interference is currently an important aspect of STAP. The discrete non-homogenates due to strong interference or target separating from clutter ridge account for much of the degradation in urban and spiky clutter scenarios. The use of adaptive weights with the hybrid algorithm is widely application to discrete non-homogeneity problems, which is a hybridization of a two-dimensional non-statistical method with statistically based methods. This paper further considers a new direct data domain processor with a prefilter attenuating clutter to strengthen suppression for discrete non-homogeneous interference. By that, the desirable performance of STAP to discrete non-homogeneous interference is observed.
STAP has been widely studied for airborne radar as an approach to adaptively detect small target competing with ground clutter. Non-homogeneous interference is currently an important aspect of STAP. The discrete non-homogenates due to strong interference or target separating from clutter ridge account for much of the degradation in urban and spiky clutter scenarios. The use of adaptive weights with the hybrid algorithm is widely application to discrete non-homogeneity problems, which is a hybridization of a two-dimensional non-statistical method with statistically based methods. This paper further considers a new direct data domain processor with a prefilter attenuating clutter to strengthen suppression for discrete non-homogeneous interference. By that, the desirable performance of STAP to discrete non-homogeneous interference is observed.
2002, 24(5): 711-715.
Abstract:
This paper discusses the phase noise filtering problem for Synthetic Aperture Radar (SAR) interferometric phase images. A new noise filtering algorithm, which can adapt to the direction of fringes, is developed. This algorithm is useful especially for tightly packed fringes. The algorithm can be carried out easily. Using SIR-C/X-SAR repeat-pass generated interferograms, the effectiveness of this filter is tested.
This paper discusses the phase noise filtering problem for Synthetic Aperture Radar (SAR) interferometric phase images. A new noise filtering algorithm, which can adapt to the direction of fringes, is developed. This algorithm is useful especially for tightly packed fringes. The algorithm can be carried out easily. Using SIR-C/X-SAR repeat-pass generated interferograms, the effectiveness of this filter is tested.
2002, 24(5): 716-720.
Abstract:
The finite difference time-domain method is used to analyse the wide-hand impedance characteristics in UHF band of the tapered slot antenna in this paper. And the SWR of a, Vivaldi antenna is calculated, is in good agreement with the experimental results. The results show that the methods of modeling in this paper are correct and valid. The antenna SWR, changes a little within two octaves, so this antenna can work in wide-baud held.
The finite difference time-domain method is used to analyse the wide-hand impedance characteristics in UHF band of the tapered slot antenna in this paper. And the SWR of a, Vivaldi antenna is calculated, is in good agreement with the experimental results. The results show that the methods of modeling in this paper are correct and valid. The antenna SWR, changes a little within two octaves, so this antenna can work in wide-baud held.
