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2010 Vol. 32, No. 2
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2010, 32(2): 255-260.
doi: 10.3724/SP.J.1146.2009.00136
Abstract:
Current stream scheduling algorithms have to compromise their performance in heterogeneous environments. A Reconfigurable Streaming Media Scheduling (RSMS) algorithm supporting user heterogeneity is proposed. The algorithm by using catching-up streams supports heterogeneous users reconfiguring catching-up streams at different transmission rates and achieves resources sharing ultimately through stream merging. The optimal multicast interval, the average server bandwidth and server bandwidth distribution for RSMS algorithm are all analyzed. The efficiency and scalability of RSMA algorithm are verified through simulation experiment.
Current stream scheduling algorithms have to compromise their performance in heterogeneous environments. A Reconfigurable Streaming Media Scheduling (RSMS) algorithm supporting user heterogeneity is proposed. The algorithm by using catching-up streams supports heterogeneous users reconfiguring catching-up streams at different transmission rates and achieves resources sharing ultimately through stream merging. The optimal multicast interval, the average server bandwidth and server bandwidth distribution for RSMS algorithm are all analyzed. The efficiency and scalability of RSMA algorithm are verified through simulation experiment.
2010, 32(2): 261-266.
doi: 10.3724/SP.J.1146.2009.00135
Abstract:
How to extract and select features from time series are two important topics in time series classification. In this paper, a MNOE (Mining Non-Overlap Episode) algorithm is presented to find non-overlap frequent patterns in time series and these non-overlap frequent patterns are considered as features of the time series. Based on these non-overlap episodes, an EGMAMC (Episode Generated Mixed memory Aggregation Markov Chain) model is presented to describe time series. According to the principle of likelihood ratio test, the connection between the support of episode and whether EGMAMC could describe the time series significantly is induced. Based on the definition of information gain, significant frequent patterns are selected as the features of time series for classification. The experiments on UCI (University of California Irvine) datasets and smart building datasets demonstrate that the classification model trained with selecting significant frequent patterns as features outperforms the one trained without selecting them on precision, recall and F-Measure. The time series classification models can be improved by efficiently extracting and effectively selecting non-overlap frequent patterns as features of time series.
How to extract and select features from time series are two important topics in time series classification. In this paper, a MNOE (Mining Non-Overlap Episode) algorithm is presented to find non-overlap frequent patterns in time series and these non-overlap frequent patterns are considered as features of the time series. Based on these non-overlap episodes, an EGMAMC (Episode Generated Mixed memory Aggregation Markov Chain) model is presented to describe time series. According to the principle of likelihood ratio test, the connection between the support of episode and whether EGMAMC could describe the time series significantly is induced. Based on the definition of information gain, significant frequent patterns are selected as the features of time series for classification. The experiments on UCI (University of California Irvine) datasets and smart building datasets demonstrate that the classification model trained with selecting significant frequent patterns as features outperforms the one trained without selecting them on precision, recall and F-Measure. The time series classification models can be improved by efficiently extracting and effectively selecting non-overlap frequent patterns as features of time series.
2010, 32(2): 267-271.
doi: 10.3724/SP.J.1146.2008.01827
Abstract:
This paper investigates the communication network flow control with strong distributed feature and hierarchical structure, a novel network flow control model is studied by using the multi-team game model, the utility function is built up on flow rate and delay to make user flow satisfy different flow proportional QoS requirement, thus the Min-Max fair flow control game model is constituted by multi-team game optimized model. The existence of the non-inferior Nash equilibrium of the proposed network flow control model is proved theoretically. The correctness of the proposed model is validated by numerical evaluation, simulation result validates the user flow utility value is Pareto optimal at the non-inferior Nash equilibrium point.
This paper investigates the communication network flow control with strong distributed feature and hierarchical structure, a novel network flow control model is studied by using the multi-team game model, the utility function is built up on flow rate and delay to make user flow satisfy different flow proportional QoS requirement, thus the Min-Max fair flow control game model is constituted by multi-team game optimized model. The existence of the non-inferior Nash equilibrium of the proposed network flow control model is proved theoretically. The correctness of the proposed model is validated by numerical evaluation, simulation result validates the user flow utility value is Pareto optimal at the non-inferior Nash equilibrium point.
2010, 32(2): 272-277.
doi: 10.3724/SP.J.1146.2009.00299
Abstract:
Current single-stage switch structure encounters its bottleneck in scalability. This paper proposes a novel central-stage buffered scalable multistage switch structure, and establishes its mathematical model by queuing theory. For the problem of cell disorder, this paper puts forward a new algorithm to maintaining packet order simply and effectively by controlling the point in input stage and central stage strictly. The results of academic analysis show that this structure could provide 100% throughput which costs less as well. The results of simulation show that this algorithm not only could provide perfect throughput performance, but also take on a better delay performance in heavy load.
Current single-stage switch structure encounters its bottleneck in scalability. This paper proposes a novel central-stage buffered scalable multistage switch structure, and establishes its mathematical model by queuing theory. For the problem of cell disorder, this paper puts forward a new algorithm to maintaining packet order simply and effectively by controlling the point in input stage and central stage strictly. The results of academic analysis show that this structure could provide 100% throughput which costs less as well. The results of simulation show that this algorithm not only could provide perfect throughput performance, but also take on a better delay performance in heavy load.
2010, 32(2): 278-283.
doi: 10.3724/SP.J.1146.2009.00071
Abstract:
In Mobile Ad hoc Networks (MANET), it is one of the dominant factors saving a nodes battery power and improving the efficiency of network bandwidth to reduce the routing overhead for a multicast routing protocol. The roles of some nodes near the paths in the maintenance of multicasting paths and the link connectivity are studied, a local flooding algorithm, namely k-constrained flooding algorithm, and a mixed flooding pattern are presented, and then a new multicast routing protocol, which is called the On-Demand Multicast Routing Protocol with Constrained Flooding (ODMRP-CF), is also proposed in this paper. In ODMRP-CF, only k-nodes near the paths can be selected to forward the control packets to enhance the flooding efficiency. Simulation results show that the ODMRP-CF can reduce significantly control overhead while keeping similar packet delivery ratio to ODMRP.
In Mobile Ad hoc Networks (MANET), it is one of the dominant factors saving a nodes battery power and improving the efficiency of network bandwidth to reduce the routing overhead for a multicast routing protocol. The roles of some nodes near the paths in the maintenance of multicasting paths and the link connectivity are studied, a local flooding algorithm, namely k-constrained flooding algorithm, and a mixed flooding pattern are presented, and then a new multicast routing protocol, which is called the On-Demand Multicast Routing Protocol with Constrained Flooding (ODMRP-CF), is also proposed in this paper. In ODMRP-CF, only k-nodes near the paths can be selected to forward the control packets to enhance the flooding efficiency. Simulation results show that the ODMRP-CF can reduce significantly control overhead while keeping similar packet delivery ratio to ODMRP.
2010, 32(2): 284-289.
doi: 10.3724/SP.J.1146.2009.00089
Abstract:
The high dynamic topology change is the main reason to cause the frequent breakages of routes of traditional on-demand routing protocols in mobile Ad hoc networks. Therefore it is significant to extend the traditional on-demand routing protocol by the link stability prediction which will improve route stability. Based on the received signal strength, the relative motions of neighbor nodes are classified into two categories: separate and near. Then in each category, the link mean duration which is used to predict the link stability is calculated on the basis of the distance between two neighbor nodes. In routing process, mid-nodes forward the received RREQ packets after a delay which is decided by the link mean duration predicted, and then with the forward rule which is proposed, a stable route can be found. Simulation results show that this extended traditional on-demand routing protocol can improve the route stability and the network performance.
The high dynamic topology change is the main reason to cause the frequent breakages of routes of traditional on-demand routing protocols in mobile Ad hoc networks. Therefore it is significant to extend the traditional on-demand routing protocol by the link stability prediction which will improve route stability. Based on the received signal strength, the relative motions of neighbor nodes are classified into two categories: separate and near. Then in each category, the link mean duration which is used to predict the link stability is calculated on the basis of the distance between two neighbor nodes. In routing process, mid-nodes forward the received RREQ packets after a delay which is decided by the link mean duration predicted, and then with the forward rule which is proposed, a stable route can be found. Simulation results show that this extended traditional on-demand routing protocol can improve the route stability and the network performance.
2010, 32(2): 290-295.
doi: 10.3724/SP.J.1146.2009.01020
Abstract:
Accessibility has enlarged the security threats in modern space communication network, various authentication and encryption solutions are to be considered and tested for possible adoption in the space context, based on widely used space link protocols. As adopted authentication mechanism andARQ characteristic of COP-1 are both error sensitive, most of the solutions proposed previously are designed oblivious of the protocol misbehavior distinguish between attack and normal interference in space channel. An innovative misbehavior detection algorithm is proposed for CCSDS TC systems, to address this problem with a hypothesis test approach based on the model of attackers behavior and space fading channel. The simulation results show the proposed algorithm can detect the attack behavior successfully and without false alarm, when facing malicious security attacks against TC transmissions towards the spacecraft.
Accessibility has enlarged the security threats in modern space communication network, various authentication and encryption solutions are to be considered and tested for possible adoption in the space context, based on widely used space link protocols. As adopted authentication mechanism andARQ characteristic of COP-1 are both error sensitive, most of the solutions proposed previously are designed oblivious of the protocol misbehavior distinguish between attack and normal interference in space channel. An innovative misbehavior detection algorithm is proposed for CCSDS TC systems, to address this problem with a hypothesis test approach based on the model of attackers behavior and space fading channel. The simulation results show the proposed algorithm can detect the attack behavior successfully and without false alarm, when facing malicious security attacks against TC transmissions towards the spacecraft.
2010, 32(2): 296-300.
doi: 10.3724/SP.J.1146.2008.01850
Abstract:
L2C is a new civilians signal, broadcast by the modernized GPS Block IIR-M satellites. In order to access acquisition performance of GPS L2C signal, the algorithm of L2C signal is discussed firstly in the paper. That is, after acquisition of CM code by using locally generated Return to Zero (RZ) CM code and FFT, the fixed relationships between CM code and CL code are used to realize acquisition of CL code. Simulation shows that this method can complete acquisition of L2C quickly and can be applied to L2C software receiver. Then the performance of this acquisition algorithm is analyzed by using statistical theory. A general method of anti-jamming capability determination is constructed that can be applied into the analysis of the anti-jamming tolerance of other GNSS signals.
L2C is a new civilians signal, broadcast by the modernized GPS Block IIR-M satellites. In order to access acquisition performance of GPS L2C signal, the algorithm of L2C signal is discussed firstly in the paper. That is, after acquisition of CM code by using locally generated Return to Zero (RZ) CM code and FFT, the fixed relationships between CM code and CL code are used to realize acquisition of CL code. Simulation shows that this method can complete acquisition of L2C quickly and can be applied to L2C software receiver. Then the performance of this acquisition algorithm is analyzed by using statistical theory. A general method of anti-jamming capability determination is constructed that can be applied into the analysis of the anti-jamming tolerance of other GNSS signals.
2010, 32(2): 301-306.
doi: 10.3724/SP.J.1146.2008.01420
Abstract:
This paper proposes an downlink cross-layer design procedure and algorithm for On-board switch scheme based on OFDM. The ultimate objective is to maximize the system downlink throughput subject to spot beam downlink transmit power constraint, downlink channel state information about each user, bit error ratio requirement of subcarrier after signal detection by users, and destination user and QoS of each service. The algorithm can adaptively allocate subcarriers and chose modulation scheme for every subcarrier among different users and services. Simulation results show that the proposed algorithm is able to guarantee consistent degree of QoS for the same service.
This paper proposes an downlink cross-layer design procedure and algorithm for On-board switch scheme based on OFDM. The ultimate objective is to maximize the system downlink throughput subject to spot beam downlink transmit power constraint, downlink channel state information about each user, bit error ratio requirement of subcarrier after signal detection by users, and destination user and QoS of each service. The algorithm can adaptively allocate subcarriers and chose modulation scheme for every subcarrier among different users and services. Simulation results show that the proposed algorithm is able to guarantee consistent degree of QoS for the same service.
2010, 32(2): 307-312.
doi: 10.3724/SP.J.1146.2008.01801
Abstract:
An optimal iterative receiver for MIMO system need exact calculation of extrinsic information in Soft-Input-Soft-Output (SISO) detector. This optimal receiver does not fit the system with large numbers of antennas and high modulation order, because its complexity increases exponentially with modulation order and antenna number. So in this paper, the estimation of extrinsic information is proved to be equal to a choice issue of a target collection, which will be obtained by Sequential Monte Carlo (SMC) sampling. But the research also indicates that the traditional sampling method can not draw a suited target collection, so a Revised SMC (R-SMC) method is proposed to approximate a finite element discrete probability space by drawn samples. Finally, an approximate computation of extrinsic information based on R-SMC sampling is applied in this new detection algorithm. By analyses, the proposed algorithms complexity is linearly proportional to the number of drawn samples. And simulation results prove that the near-optimal Bit-Error-Ratio (BER) performance can be obtained by a small number of samples.
An optimal iterative receiver for MIMO system need exact calculation of extrinsic information in Soft-Input-Soft-Output (SISO) detector. This optimal receiver does not fit the system with large numbers of antennas and high modulation order, because its complexity increases exponentially with modulation order and antenna number. So in this paper, the estimation of extrinsic information is proved to be equal to a choice issue of a target collection, which will be obtained by Sequential Monte Carlo (SMC) sampling. But the research also indicates that the traditional sampling method can not draw a suited target collection, so a Revised SMC (R-SMC) method is proposed to approximate a finite element discrete probability space by drawn samples. Finally, an approximate computation of extrinsic information based on R-SMC sampling is applied in this new detection algorithm. By analyses, the proposed algorithms complexity is linearly proportional to the number of drawn samples. And simulation results prove that the near-optimal Bit-Error-Ratio (BER) performance can be obtained by a small number of samples.
2010, 32(2): 313-317.
doi: 10.3724/SP.J.1146.2009.00140
Abstract:
For UWB positioning system based on time delay estimation, there must be multiple reference nodes which increase the cost of system. If the reference source node can estimate the Time Of Arrival (TOA) and Direction Of Arrival (DOA) together, the location of the target can be obtained with only one reference node. In this paper, a UWB positioning system based on joint TOA and DOA estimation is proposed. The algorithm of estimation is based on Matrix Pencil (MP), and then relative coordinates of the target can be obtained. The advantage of the approach with one receiver is low cost for system. Through simulations, it is proved that the accuracy of delay and angle estimation is good, and positioning accuracy can achieve centimeter-level. It is available and practical method of UWB positioning systems which is proposed in this paper.
For UWB positioning system based on time delay estimation, there must be multiple reference nodes which increase the cost of system. If the reference source node can estimate the Time Of Arrival (TOA) and Direction Of Arrival (DOA) together, the location of the target can be obtained with only one reference node. In this paper, a UWB positioning system based on joint TOA and DOA estimation is proposed. The algorithm of estimation is based on Matrix Pencil (MP), and then relative coordinates of the target can be obtained. The advantage of the approach with one receiver is low cost for system. Through simulations, it is proved that the accuracy of delay and angle estimation is good, and positioning accuracy can achieve centimeter-level. It is available and practical method of UWB positioning systems which is proposed in this paper.
2010, 32(2): 318-322.
doi: 10.3724/SP.J.1146.2008.01575
Abstract:
By using word-oriented fault model and the technique of differential cryptanalysis, the security of SHACAL-2 against differential fault analysis is evaluated. Result shows that SHACAL-2 is not immune to such kind of attack. 8 faulty ciphertexts can recover a sub key of 32 bit on average and 128 faulty ciphertexts are needed to recover all the 512 bit keys.
By using word-oriented fault model and the technique of differential cryptanalysis, the security of SHACAL-2 against differential fault analysis is evaluated. Result shows that SHACAL-2 is not immune to such kind of attack. 8 faulty ciphertexts can recover a sub key of 32 bit on average and 128 faulty ciphertexts are needed to recover all the 512 bit keys.
2010, 32(2): 323-328.
doi: 10.3724/SP.J.1146.2008.01399
Abstract:
Steganography based on Quantization Index Modulation (QIM) is being increasingly threatened by steganalysis. This paper improves the existing steganographic methods embedding data in Non-uniform Discrete Cosine Transform (NDCT) domain instead of more commonly used Discrete Cosine Transform (DCT) domain, and proposes the NDCT-QIM image steganography which uses the parameters of NDCT as its secret key. Since the embedded signal disperses in the domain guessed by an attacker, the NDCT-QIM method makes steganalysis difficult to detect the characteristics of steganography. The analysis and experiments show that it improves the covertness of embedded signal, and is more resistant to the commonly used steganalysis methods, including those respectively based on testing gradient energy, histogram, wavelet characteristics, etc.
Steganography based on Quantization Index Modulation (QIM) is being increasingly threatened by steganalysis. This paper improves the existing steganographic methods embedding data in Non-uniform Discrete Cosine Transform (NDCT) domain instead of more commonly used Discrete Cosine Transform (DCT) domain, and proposes the NDCT-QIM image steganography which uses the parameters of NDCT as its secret key. Since the embedded signal disperses in the domain guessed by an attacker, the NDCT-QIM method makes steganalysis difficult to detect the characteristics of steganography. The analysis and experiments show that it improves the covertness of embedded signal, and is more resistant to the commonly used steganalysis methods, including those respectively based on testing gradient energy, histogram, wavelet characteristics, etc.
2010, 32(2): 329-334.
doi: 10.3724/SP.J.1146.2009.00094
Abstract:
This paper addresses new hop rate estimation schemes for hybrid DS/FH_BPSK signals which employ a novel channelized spectral enhancement preprocessor and time-frequency analysis. Good performance is achieved by following three stages. Firstly, a nonlinear process is used to produce the reference signal which has the same hop rate as the original signal and its frequencies could be estimated by the cyclic spectrum. Then a novel Externally-Linear-Internally-Nonlinear(ELIN) channelized spectral enhancement system is employed to realize interference-suppression and enhance noisy signal without losing detail information. Finally, based on the reliable signal enhancement results, SPWVD(Smooth-Pseudo-Wigner-Ville Distribution) is used to estimate the hop rate of the hybrid DS/FH spread spectrum signal. Since no prior information of signals are needed, the proposed method is easy to implement for the reconnaissance receiver. The simulation results show that the proposed method can operate effectively even under low SNR conditions.
This paper addresses new hop rate estimation schemes for hybrid DS/FH_BPSK signals which employ a novel channelized spectral enhancement preprocessor and time-frequency analysis. Good performance is achieved by following three stages. Firstly, a nonlinear process is used to produce the reference signal which has the same hop rate as the original signal and its frequencies could be estimated by the cyclic spectrum. Then a novel Externally-Linear-Internally-Nonlinear(ELIN) channelized spectral enhancement system is employed to realize interference-suppression and enhance noisy signal without losing detail information. Finally, based on the reliable signal enhancement results, SPWVD(Smooth-Pseudo-Wigner-Ville Distribution) is used to estimate the hop rate of the hybrid DS/FH spread spectrum signal. Since no prior information of signals are needed, the proposed method is easy to implement for the reconnaissance receiver. The simulation results show that the proposed method can operate effectively even under low SNR conditions.
2010, 32(2): 335-339.
doi: 10.3724/SP.J.1146.2009.00533
Abstract:
In this paper, an approach called generating function is proposed to construct Golay pair of length 2n and its mate based on conventional interleaving and concatenation method. Relationship between generating function of Golay pair and Sylvester Hadamard matrix is also investigated, which not only helps to calculate the total number of Golay pair of specific length, but also helps to apply Hadamard factorization to Golay pair generation. Based on generating function, lots of Golay pair can be produced conveniently for multi-target applications. Generating functions are expressed by binary vector, XOR and AND operations, which greatly facilitates the physical implementation of sequence generation.
In this paper, an approach called generating function is proposed to construct Golay pair of length 2n and its mate based on conventional interleaving and concatenation method. Relationship between generating function of Golay pair and Sylvester Hadamard matrix is also investigated, which not only helps to calculate the total number of Golay pair of specific length, but also helps to apply Hadamard factorization to Golay pair generation. Based on generating function, lots of Golay pair can be produced conveniently for multi-target applications. Generating functions are expressed by binary vector, XOR and AND operations, which greatly facilitates the physical implementation of sequence generation.
2010, 32(2): 340-344.
doi: 10.3724/SP.J.1146.2008.01287
Abstract:
A concatenated code model is proposed for high-order Low-Density Parity-Check (LDPC) coded- modulation scheme. This model is comprised of a serial concatenation of an outer LDPC encoder, an inner Binary-Decimal Conversion (BDC) encoder and a puncture device. A joint parity-check matrix is derived for the concatenated code, and the corresponding joint demodulation and decoding algorithm, named Concatenated-Code Belief Propagation (CCBP), is presented. Simulation results show that this LDPC coded modulation scheme with the CCBP algorithm provides effective improvements relative to the Bit Interleaved Coded Modulation (BICM) scheme for high-order modulations.
A concatenated code model is proposed for high-order Low-Density Parity-Check (LDPC) coded- modulation scheme. This model is comprised of a serial concatenation of an outer LDPC encoder, an inner Binary-Decimal Conversion (BDC) encoder and a puncture device. A joint parity-check matrix is derived for the concatenated code, and the corresponding joint demodulation and decoding algorithm, named Concatenated-Code Belief Propagation (CCBP), is presented. Simulation results show that this LDPC coded modulation scheme with the CCBP algorithm provides effective improvements relative to the Bit Interleaved Coded Modulation (BICM) scheme for high-order modulations.
2010, 32(2): 345-349.
doi: 10.3724/SP.J.1146.2008.01157
Abstract:
Burst detection plays a crucial role for burst-mode demodulation, which helps the acquisition and synchronization of data bursts. Most conventional Data-Aided (DA) burst detection approaches demands timing, and the performance degrades severely in the presence of frequency offset. This paper proposes a burst detection algorithm based on the Average-Likelihood-Ratio-Test (ALRT) for over-sampled modulated signals with timing uncompleted. The proposed algorithm outperforms the previously proposed algorithms and is robust to the frequency offset. Furthermore, the dependence of false alarm rate on SNR is slight.
Burst detection plays a crucial role for burst-mode demodulation, which helps the acquisition and synchronization of data bursts. Most conventional Data-Aided (DA) burst detection approaches demands timing, and the performance degrades severely in the presence of frequency offset. This paper proposes a burst detection algorithm based on the Average-Likelihood-Ratio-Test (ALRT) for over-sampled modulated signals with timing uncompleted. The proposed algorithm outperforms the previously proposed algorithms and is robust to the frequency offset. Furthermore, the dependence of false alarm rate on SNR is slight.
2010, 32(2): 350-354.
doi: 10.3724/SP.J.1146.2009.00125
Abstract:
Detection of the number of spatial signals is one of the key issues in array signal processing community. Most of the existing methods for detection of the number of signal sources require the eigenvalues of the sample covariance matrix. In this paper, a Fast Detection Method via Modified Hung-Turner Projection (FDM-MHTP) is proposed to dectect the number of multiple emitters, where a threshold is derived exploiting the asymptotic distribution properties of the estimation errors of the sample covariance matrix. The threshold is utilized to detect the number of signal sources in conjunction with performing Gram-Schmidt(GS) orthogonalization. Without eigenvalue decomposition, the algorithm has good detection performance and low computation complexity. Computer simulation shows the correctness and efficiency of the algorithm.
Detection of the number of spatial signals is one of the key issues in array signal processing community. Most of the existing methods for detection of the number of signal sources require the eigenvalues of the sample covariance matrix. In this paper, a Fast Detection Method via Modified Hung-Turner Projection (FDM-MHTP) is proposed to dectect the number of multiple emitters, where a threshold is derived exploiting the asymptotic distribution properties of the estimation errors of the sample covariance matrix. The threshold is utilized to detect the number of signal sources in conjunction with performing Gram-Schmidt(GS) orthogonalization. Without eigenvalue decomposition, the algorithm has good detection performance and low computation complexity. Computer simulation shows the correctness and efficiency of the algorithm.
2010, 32(2): 355-359.
doi: 10.3724/SP.J.1146.2009.00072
Abstract:
Signals with sinusoid modulated phase is the general form of micro-Doppler signals in radar echoes from targets with micro-motions. This paper derives the cycle spectra of this signal using its cyclostationary character, and estimates the parameters of the signal from the cycle spectra. Compared with conventional spectra analysis methods, this parameter estimation method based on cyclostationary spectra can suppress stationary noise more effectively. Finally, the theoretic deduction and the error curves by simulations prove the validity of the process.
Signals with sinusoid modulated phase is the general form of micro-Doppler signals in radar echoes from targets with micro-motions. This paper derives the cycle spectra of this signal using its cyclostationary character, and estimates the parameters of the signal from the cycle spectra. Compared with conventional spectra analysis methods, this parameter estimation method based on cyclostationary spectra can suppress stationary noise more effectively. Finally, the theoretic deduction and the error curves by simulations prove the validity of the process.
2010, 32(2): 360-365.
doi: 10.3724/SP.J.1146.2008.01830
Abstract:
This paper presents a new image denoising scheme by combining the NonSubsampled Contourlet Transform (NSCT) and adaptive total variation model. The original image is first decomposed using NSCT and the image model is built based on Gaussian Scale Mixtures (GSM) model. Then the image noises are removed using Bayesian estimation, producing the preliminary denoised image after reconstruction. Then the preliminary primary denoised image is further filtered using the adaptive total variation model, producing the final denoised image. Experiments show that the proposed scheme can remove Gibbs-like artifacts and image noise effectively. Besides, it outperforms the existing schemes in regard of both the Peak-Signal-to-Noise-Ratio (PSNR) and the edge preservation ability.
This paper presents a new image denoising scheme by combining the NonSubsampled Contourlet Transform (NSCT) and adaptive total variation model. The original image is first decomposed using NSCT and the image model is built based on Gaussian Scale Mixtures (GSM) model. Then the image noises are removed using Bayesian estimation, producing the preliminary denoised image after reconstruction. Then the preliminary primary denoised image is further filtered using the adaptive total variation model, producing the final denoised image. Experiments show that the proposed scheme can remove Gibbs-like artifacts and image noise effectively. Besides, it outperforms the existing schemes in regard of both the Peak-Signal-to-Noise-Ratio (PSNR) and the edge preservation ability.
2010, 32(2): 366-370.
doi: 10.3724/SP.J.1146.2009.00044
Abstract:
The phased array radar with adaptive digital beamforming usually adopts subarray configuration. Subarray configuration has obvious influence on system performance, therefore the optimal subarray division has important significance in both theoretics and applications. Based on Multi-Objective Evolutionary Algorithm(MOEA), the subarray configuration is optimized to obtain anti-jamming performance and sidelobe level of patterns of sum and difference beam in case of mainlobe jamming as good as possible. The sidelobe level of adaptive pattern of sum beam, output SINR and sidelobe level of difference beam are taken as optimized objectives, and five objective functions are constructed. The encoding for subarray configuration used in MOEA are proposed. Simulation results of that an planar array is segmented into 64 subarrays by using MOEA based on Pareto rank sorting demonstrate that, a variety of performances of system are improved at the same time.
The phased array radar with adaptive digital beamforming usually adopts subarray configuration. Subarray configuration has obvious influence on system performance, therefore the optimal subarray division has important significance in both theoretics and applications. Based on Multi-Objective Evolutionary Algorithm(MOEA), the subarray configuration is optimized to obtain anti-jamming performance and sidelobe level of patterns of sum and difference beam in case of mainlobe jamming as good as possible. The sidelobe level of adaptive pattern of sum beam, output SINR and sidelobe level of difference beam are taken as optimized objectives, and five objective functions are constructed. The encoding for subarray configuration used in MOEA are proposed. Simulation results of that an planar array is segmented into 64 subarrays by using MOEA based on Pareto rank sorting demonstrate that, a variety of performances of system are improved at the same time.
2010, 32(2): 371-376.
doi: 10.3724/SP.J.1146.2009.00017
Abstract:
This paper mainly studies the application of the combination of Hurst exponent and variable step-size LMS algorithm in low-observable target detection in sea clutter. Up to now, fractal theory and statistic theory are applied to target detection respectively. In this paper, the fractal-based variable step-size Least Mean Square (LMS) algorithm is introduced and a novel low-observable target detection model is proposed based on the algorithm. And the combination of LMS algorithm and single fractal characteristic in target detection is elementarily realized. Finally, X-band real sea clutter is used for verification and the results indicate that the proposed model has a good performance of detecting low-observable target in sea clutter.
This paper mainly studies the application of the combination of Hurst exponent and variable step-size LMS algorithm in low-observable target detection in sea clutter. Up to now, fractal theory and statistic theory are applied to target detection respectively. In this paper, the fractal-based variable step-size Least Mean Square (LMS) algorithm is introduced and a novel low-observable target detection model is proposed based on the algorithm. And the combination of LMS algorithm and single fractal characteristic in target detection is elementarily realized. Finally, X-band real sea clutter is used for verification and the results indicate that the proposed model has a good performance of detecting low-observable target in sea clutter.
2010, 32(2): 377-382.
doi: 10.3724/SP.J.1146.2009.00024
Abstract:
Noise Frequency Modulated Continuous Wave (FMCW) radar has an ideal thumbtack ambiguity function, and unambiguous measurement of distance and velocity due to the nonperiodicity of its transmitting signal, so it is suitable for detecting high-speed and long-distance targets on orbit in principle. The high speed moving targets echo signals of Noise FMCW are generated by interpolation in this paper. An approach to improve the main-to-sidelobe ratio by utilizing Matched reference signal to correct the range migration in Noise FMCW and single frequency combined radar system is presented. The FFT-IFFT technique and Clean method are used to enlarge the dynamic range. Simulation results verify the effectiveness of this new method.
Noise Frequency Modulated Continuous Wave (FMCW) radar has an ideal thumbtack ambiguity function, and unambiguous measurement of distance and velocity due to the nonperiodicity of its transmitting signal, so it is suitable for detecting high-speed and long-distance targets on orbit in principle. The high speed moving targets echo signals of Noise FMCW are generated by interpolation in this paper. An approach to improve the main-to-sidelobe ratio by utilizing Matched reference signal to correct the range migration in Noise FMCW and single frequency combined radar system is presented. The FFT-IFFT technique and Clean method are used to enlarge the dynamic range. Simulation results verify the effectiveness of this new method.
2010, 32(2): 383-387.
doi: 10.3724/SP.J.1146.2009.00102
Abstract:
This paper firstly setups the geometric model of the tandem bistatic squint SAR and presents the mathematic expression of the radar echoes, then its two-dimensional frequency spectrum is derived and its characteristic is analyzed. In two-dimensional frequency domain, the point targets in the center of the observed scene is precisely imaged by using the focusing function, then the Chirp-Z transform is used to correct the range cell migration of the target echoes in both side of the center points. Finally, the radar images are obtained by the inverse Fourier transform on the azimuth direction. Since the algorithm uses the property of the Chirp-Z transform processing the nonlinear modulation frequency signal, the processing procedure is simplified and the imaging precision is greatly improved. The simulation tests validate this new algorithm based on the Chirp-Z transform to process the data of the tandem bistatic squint SAR.
This paper firstly setups the geometric model of the tandem bistatic squint SAR and presents the mathematic expression of the radar echoes, then its two-dimensional frequency spectrum is derived and its characteristic is analyzed. In two-dimensional frequency domain, the point targets in the center of the observed scene is precisely imaged by using the focusing function, then the Chirp-Z transform is used to correct the range cell migration of the target echoes in both side of the center points. Finally, the radar images are obtained by the inverse Fourier transform on the azimuth direction. Since the algorithm uses the property of the Chirp-Z transform processing the nonlinear modulation frequency signal, the processing procedure is simplified and the imaging precision is greatly improved. The simulation tests validate this new algorithm based on the Chirp-Z transform to process the data of the tandem bistatic squint SAR.
2010, 32(2): 388-393.
doi: 10.3724/SP.J.1146.2009.00095
Abstract:
In order to remove the fluctuant interference such as swaying branches，stochastic shaking of camera in complex environments when moving targets are detected in video sequences, A new algorithm of moving targets detection based on video windows partition and classification is proposed. First of all, the image sequences are divided into numbers of video windows at size rc. Then the simple statistical feature is extracted from the matrix of accumulated frame differences in the window. According to the feature, the video windows is divided into two categories in each frame，moving object windows and non-moving object windows including static background windows and fluctuant interference windows. Finally all moving object windows are merged into the moving targets. The advantage of this method is that no knowledge about the background model and object size or shape is necessary. The results show that the algorithm can rapidly and validly detect the moving objects in complex environments with the fluctuant interference such as swaying branches and stochastic shaking of camera.
In order to remove the fluctuant interference such as swaying branches，stochastic shaking of camera in complex environments when moving targets are detected in video sequences, A new algorithm of moving targets detection based on video windows partition and classification is proposed. First of all, the image sequences are divided into numbers of video windows at size rc. Then the simple statistical feature is extracted from the matrix of accumulated frame differences in the window. According to the feature, the video windows is divided into two categories in each frame，moving object windows and non-moving object windows including static background windows and fluctuant interference windows. Finally all moving object windows are merged into the moving targets. The advantage of this method is that no knowledge about the background model and object size or shape is necessary. The results show that the algorithm can rapidly and validly detect the moving objects in complex environments with the fluctuant interference such as swaying branches and stochastic shaking of camera.
2010, 32(2): 394-399.
doi: 10.3724/SP.J.1146.2009.00115
Abstract:
Compositing is the most common form of digital image forging. For a class of JPEG image forgery, a simple and effective detecting algorithm is proposed on the basis of inconsistencies of blocking artifacts between tampered region and non-tampered region. Firstly, a testing image is cropped and recompressed with the estimated primary quality factor. Secondly, blocking artifacts factor map is extracted via computing the distortion caused by recompression. Finally, automatic detection and location of tampered region is realized by using image segmentation. Experimental results demonstrate that the proposed approach is applicable to images of various qualities and lesser-tampered regions. When the difference of quality factors between double compression and single compression is greater than 15, the accuracy reaches above 93% with a less than 5% false positive rate.
Compositing is the most common form of digital image forging. For a class of JPEG image forgery, a simple and effective detecting algorithm is proposed on the basis of inconsistencies of blocking artifacts between tampered region and non-tampered region. Firstly, a testing image is cropped and recompressed with the estimated primary quality factor. Secondly, blocking artifacts factor map is extracted via computing the distortion caused by recompression. Finally, automatic detection and location of tampered region is realized by using image segmentation. Experimental results demonstrate that the proposed approach is applicable to images of various qualities and lesser-tampered regions. When the difference of quality factors between double compression and single compression is greater than 15, the accuracy reaches above 93% with a less than 5% false positive rate.
2010, 32(2): 400-404.
doi: 10.3724/SP.J.1146.2009.00068
Abstract:
For fluid motion image computation (PIV), a nonlinear filtering based PIV approach was proposed which can obtain reliable motion vector, div and curl fileds. As variational based PIV approaches the new approach is a nonlinear filtering process instead of an energy minimizing process, which can overcome the shortage of correlation based PIV approaches and avoid the restrictions of convexity and differentiability required by classical variational approaches. Experimental results from real particle image sequences demonstrated that the new method can help to suppress the computation noise and increase the reliability of fluid motion characteristic and structural descriptions.
For fluid motion image computation (PIV), a nonlinear filtering based PIV approach was proposed which can obtain reliable motion vector, div and curl fileds. As variational based PIV approaches the new approach is a nonlinear filtering process instead of an energy minimizing process, which can overcome the shortage of correlation based PIV approaches and avoid the restrictions of convexity and differentiability required by classical variational approaches. Experimental results from real particle image sequences demonstrated that the new method can help to suppress the computation noise and increase the reliability of fluid motion characteristic and structural descriptions.
2010, 32(2): 405-410.
doi: 10.3724/SP.J.1146.2009.00099
Abstract:
To address the lattice size exponential explosion problem in large scale data and rule mining, concept coverage density function and measurement model are introduced to reduce redundant concepts. The pruned lattice, named marked-concept lattice, has linear space complexity and can be obtained through direct or synchronous construction or node-extraction. Analysis and simulation tests show that this reduction model not only significantly reduces normal concept lattice size, but also significantly improves lattice building and rule mining efficiency. Furthermore, marked concept carries crucial information and physical meanings, thus can make benefits for Web service relationship mining.
To address the lattice size exponential explosion problem in large scale data and rule mining, concept coverage density function and measurement model are introduced to reduce redundant concepts. The pruned lattice, named marked-concept lattice, has linear space complexity and can be obtained through direct or synchronous construction or node-extraction. Analysis and simulation tests show that this reduction model not only significantly reduces normal concept lattice size, but also significantly improves lattice building and rule mining efficiency. Furthermore, marked concept carries crucial information and physical meanings, thus can make benefits for Web service relationship mining.
2010, 32(2): 411-415.
doi: 10.3724/SP.J.1146.2008.01740
Abstract:
Object tracking by using single color feature results in a poor performance in robustness. To solve this problem, an object tracking method based on multi-features fusion is presented. The proposed method uses the color and texture features extracted by Local Binary Pattern(LBP) to present the interested target, performs a feature fusion in mean-shift and particle filter algorithms, and efficiently avoids the unstable problems via using single color feature for representation. The two common used fusion rules are used,thus overcoming the degeneracy problem and resulting in low computational cost. Experimental results indicate the proposed method is more robust to present object and has good performance in complex scene.
Object tracking by using single color feature results in a poor performance in robustness. To solve this problem, an object tracking method based on multi-features fusion is presented. The proposed method uses the color and texture features extracted by Local Binary Pattern(LBP) to present the interested target, performs a feature fusion in mean-shift and particle filter algorithms, and efficiently avoids the unstable problems via using single color feature for representation. The two common used fusion rules are used,thus overcoming the degeneracy problem and resulting in low computational cost. Experimental results indicate the proposed method is more robust to present object and has good performance in complex scene.
2010, 32(2): 416-421.
doi: 10.3724/SP.J.1146.2008.01461
Abstract:
It is important to locate the center of distorted pupil in eye tracking process. To tackle the issues induced by distortion and disturbance, a new Random Sample Consensus algorithm based on only 3 points, named RANSAC_3, is proposed in this paper. Ellipse model is adopted to match the distorted pupil, its parameters are calculated from the two randomly sampled points and one searched point. Only two randomly sampled points are needed to estimate the ellipse parameters in this method, so the probability of sampling disturbing points is reduced. The point derived by searching can be used to determine whether to calculate the ellipse parameters, so the efficiency of ellipse fitting and the accuracy of localization are improved. Experimental results show that the method has pretty good performance on the localization of distorted pupils, and is effective and robust to various disturbances, i.e. spectrum reflection, eyelash, hair, glasses and motion blur. Moreover, its high speed ensures that it can be used in a real-time eye tracking system.
It is important to locate the center of distorted pupil in eye tracking process. To tackle the issues induced by distortion and disturbance, a new Random Sample Consensus algorithm based on only 3 points, named RANSAC_3, is proposed in this paper. Ellipse model is adopted to match the distorted pupil, its parameters are calculated from the two randomly sampled points and one searched point. Only two randomly sampled points are needed to estimate the ellipse parameters in this method, so the probability of sampling disturbing points is reduced. The point derived by searching can be used to determine whether to calculate the ellipse parameters, so the efficiency of ellipse fitting and the accuracy of localization are improved. Experimental results show that the method has pretty good performance on the localization of distorted pupils, and is effective and robust to various disturbances, i.e. spectrum reflection, eyelash, hair, glasses and motion blur. Moreover, its high speed ensures that it can be used in a real-time eye tracking system.
2010, 32(2): 422-426.
doi: 10.3724/SP.J.1146.2008.01088
Abstract:
An image fusion algorithm in nonsubsampled Contourlet domain is presented based on Human Visual System (HVS) and source image characteristics. Moreover, the influence on fusion result of decomposition levels and directional decomposition numbers is discussed. Closed Loop Feedback (CLF) is introduced into low-pass subbands to obtain optimal fused weights adaptively. In high-pass subbands, Activity Measure (AM) is defined based on region energy to enhance contrast of fused images and protect detail information of source images. Experiment results show that the proposed fusion technique is robust and the fusion images have ideal clear and continue edges.
An image fusion algorithm in nonsubsampled Contourlet domain is presented based on Human Visual System (HVS) and source image characteristics. Moreover, the influence on fusion result of decomposition levels and directional decomposition numbers is discussed. Closed Loop Feedback (CLF) is introduced into low-pass subbands to obtain optimal fused weights adaptively. In high-pass subbands, Activity Measure (AM) is defined based on region energy to enhance contrast of fused images and protect detail information of source images. Experiment results show that the proposed fusion technique is robust and the fusion images have ideal clear and continue edges.
2010, 32(2): 427-432.
doi: 10.3724/SP.J.1146.2008.00983
Abstract:
To deal with the false and unstable corners, high computational complexity and incorrect matching, a new image registration algorithm is proposed based on corners which are well-distributed in image and with sub-pixel localization precision. Firstly corners in an image are detected by multi-scale Harris operator, which are taken as initial interest points. And then adaptive non-maximal suppression is used to limit the number of interest points, so the computational complexity is decreased and the efficiency of the algorithm is improved. At the mean time, the corners are made to be well-distributed in image. Since the location of initial Harris corners have offset and false corners have existed, sub-pixel localization technique is applied to determine the location of corners and eliminate the false and unstable corners in this process. Finally, RANSAC is used to estimate the parameters robustly based on initial matching. Experiments showed that the proposed algorithm has a good performance of efficiency, accuracy and robustness.
To deal with the false and unstable corners, high computational complexity and incorrect matching, a new image registration algorithm is proposed based on corners which are well-distributed in image and with sub-pixel localization precision. Firstly corners in an image are detected by multi-scale Harris operator, which are taken as initial interest points. And then adaptive non-maximal suppression is used to limit the number of interest points, so the computational complexity is decreased and the efficiency of the algorithm is improved. At the mean time, the corners are made to be well-distributed in image. Since the location of initial Harris corners have offset and false corners have existed, sub-pixel localization technique is applied to determine the location of corners and eliminate the false and unstable corners in this process. Finally, RANSAC is used to estimate the parameters robustly based on initial matching. Experiments showed that the proposed algorithm has a good performance of efficiency, accuracy and robustness.
2010, 32(2): 433-438.
doi: 10.3724/SP.J.1146.2009.00064
Abstract:
This paper is concerned with the problem of handwritten digits recognition in high dimensional feature space. The residual feature information may bring undesirable complexity to the underlying probability distribution of the concept label for learning algorithm to capture. The recognition accuracy and efficiency of the so trained learning model are usually depressed. According to this situation, an improved confusion-crossed support vector machine tree is proposed. A feature selection process based on the sensitivity of the margin to a feature is presented for the training step of each support vector machine embedded in each internal node. The experimental results on optical handwritten digits recognition problem in UCI database indicate that the proposed approach achieves competitive or even better recognition accuracy in the condensed feature space. Further, it also obtains lower structure complexity on internal nodes and the whole hybrid learning model than the compared approaches.
This paper is concerned with the problem of handwritten digits recognition in high dimensional feature space. The residual feature information may bring undesirable complexity to the underlying probability distribution of the concept label for learning algorithm to capture. The recognition accuracy and efficiency of the so trained learning model are usually depressed. According to this situation, an improved confusion-crossed support vector machine tree is proposed. A feature selection process based on the sensitivity of the margin to a feature is presented for the training step of each support vector machine embedded in each internal node. The experimental results on optical handwritten digits recognition problem in UCI database indicate that the proposed approach achieves competitive or even better recognition accuracy in the condensed feature space. Further, it also obtains lower structure complexity on internal nodes and the whole hybrid learning model than the compared approaches.
2010, 32(2): 439-443.
doi: 10.3724/SP.J.1146.2009.00142
Abstract:
This paper presents a universality method for measure of security in steganography. According to the definition of K-L divergence and the properties of security in steganography, some limitations in Cachins definition of security are shown in the beginning. Besides the divergence of probability distributions between stego and cover, the sample size and the cardinality of the state set of random variable have great effect on security in steganography. Based on K-L divergence and hypothesis testing, an amended measure of security and a useful illation are presented. The result of examination can prove that the new measure of security is reasonable.
This paper presents a universality method for measure of security in steganography. According to the definition of K-L divergence and the properties of security in steganography, some limitations in Cachins definition of security are shown in the beginning. Besides the divergence of probability distributions between stego and cover, the sample size and the cardinality of the state set of random variable have great effect on security in steganography. Based on K-L divergence and hypothesis testing, an amended measure of security and a useful illation are presented. The result of examination can prove that the new measure of security is reasonable.
2010, 32(2): 444-448.
doi: 10.3724/SP.J.1146.2009.00263
Abstract:
The existing fault-tolerant scheduling algorithms are mainly based on primary/backup copies technology and the utilization of processor decreases greatly with the number of faults increases. In this paper, a real-time fault-tolerant scheduling algorithm is proposed to schedule periodic and aperiodic tasks jointly and tolerate multiple processor faults. The DS (Deferrable Server) algorithm is extended to the multiprocessors system, and several deferrable servers can be set to schedule aperiodic tasks. The faults can be tolerated by tasks rollback executing on the other processors. The experimental results demonstrate that this algorithm can guarantee all accepted tasks deadlines and decreases the number of required processor significantly.
The existing fault-tolerant scheduling algorithms are mainly based on primary/backup copies technology and the utilization of processor decreases greatly with the number of faults increases. In this paper, a real-time fault-tolerant scheduling algorithm is proposed to schedule periodic and aperiodic tasks jointly and tolerate multiple processor faults. The DS (Deferrable Server) algorithm is extended to the multiprocessors system, and several deferrable servers can be set to schedule aperiodic tasks. The faults can be tolerated by tasks rollback executing on the other processors. The experimental results demonstrate that this algorithm can guarantee all accepted tasks deadlines and decreases the number of required processor significantly.
2010, 32(2): 449-453.
doi: 10.3724/SP.J.1146.2009.00096
Abstract:
The high-frequency method for solving the scattering from electrically large conductive targets in half space is presented in this paper. The High-frequency method is deduced by introducing the half-space Greens function into the conventional method of physical optics, method of equivalent currents. Combined with the graphical-electromagnetic computing method and ray tracing technique that account for shadowing, multiple scattering in half space, one may calculate the radar cross-section of a conductive targets object in a half space. The numerical results show that this method is efficient and accurate.
The high-frequency method for solving the scattering from electrically large conductive targets in half space is presented in this paper. The High-frequency method is deduced by introducing the half-space Greens function into the conventional method of physical optics, method of equivalent currents. Combined with the graphical-electromagnetic computing method and ray tracing technique that account for shadowing, multiple scattering in half space, one may calculate the radar cross-section of a conductive targets object in a half space. The numerical results show that this method is efficient and accurate.
2010, 32(2): 454-458.
doi: 10.3724/SP.J.1146.2009.00111
Abstract:
Photonic BandGap (PBG) is man-made periodic dielectric structure, which may control the propagation of electromagnetic waves in certain frequency range. And the Uniplanar Compact Photonic BandGap (UC-PBG) is a periodic photonic bandgap on a conductor-backed dielectric substrate. This paper introduces a waveguide using the UC-PBG structure, which replace the two bilateral sides of a rectangular waveguide. The simulations with Ansoft HFSS indicate that the TE10 mode can be converted to quasi-TEM mode in the range of 15.15 GHz-15.60 GHz with the UC-PBG structure.
Photonic BandGap (PBG) is man-made periodic dielectric structure, which may control the propagation of electromagnetic waves in certain frequency range. And the Uniplanar Compact Photonic BandGap (UC-PBG) is a periodic photonic bandgap on a conductor-backed dielectric substrate. This paper introduces a waveguide using the UC-PBG structure, which replace the two bilateral sides of a rectangular waveguide. The simulations with Ansoft HFSS indicate that the TE10 mode can be converted to quasi-TEM mode in the range of 15.15 GHz-15.60 GHz with the UC-PBG structure.
2010, 32(2): 459-463.
doi: 10.3724/SP.J.1146.2008.00233
Abstract:
Based on the linear theory of gyro-TWA, this paper is focused on the numerical simulations for the relations of the starting length and starting frequency with beam radius, voltage, velocity ratio, beam current and magnetic field for a gyro-BWO operating in the TE21 mode at fundamental or second harmonic and the corresponding physical mechanisms is explained. And the effect of distributed wall losses on the suppression of the TE21 mode gyro-BWO is discussed. The results in this paper are helpful for the design of gyro-TWA and gyro-BWOs.
Based on the linear theory of gyro-TWA, this paper is focused on the numerical simulations for the relations of the starting length and starting frequency with beam radius, voltage, velocity ratio, beam current and magnetic field for a gyro-BWO operating in the TE21 mode at fundamental or second harmonic and the corresponding physical mechanisms is explained. And the effect of distributed wall losses on the suppression of the TE21 mode gyro-BWO is discussed. The results in this paper are helpful for the design of gyro-TWA and gyro-BWOs.
2010, 32(2): 464-469.
doi: 10.3724/SP.J.1146.2009.00116
Abstract:
For audio signals with input frequency between 20 Hz and 24 kHz, a switch-capacitor feed-forward A/D modulator in 0.18m Logic technology is proposed in this paper, which gains 16 bit resolution with 1.2 V supply voltage. The modulator can achieve 102.2 dB signal-to-noise ratio (SNR) under 6MHz sample clock, and the total power dissipation is only 2.46 mW. In the modulator, a pseudo-two-stage Class-AB transconductance amplifier is used, which has high slew rate and open loop gain while without increasing power dissipation. What is more, full compensated depletion-mode capacitors are used as sample capacitors and integrating capacitors to enable the whole chip to be fabricated in standard digital technology, which is good to reduce chip cost and improve the modulators compatibility in technology. Compared with other low-power low-voltage A/D modulators reported, this design has better FOM (Figure Of Merit).
For audio signals with input frequency between 20 Hz and 24 kHz, a switch-capacitor feed-forward A/D modulator in 0.18m Logic technology is proposed in this paper, which gains 16 bit resolution with 1.2 V supply voltage. The modulator can achieve 102.2 dB signal-to-noise ratio (SNR) under 6MHz sample clock, and the total power dissipation is only 2.46 mW. In the modulator, a pseudo-two-stage Class-AB transconductance amplifier is used, which has high slew rate and open loop gain while without increasing power dissipation. What is more, full compensated depletion-mode capacitors are used as sample capacitors and integrating capacitors to enable the whole chip to be fabricated in standard digital technology, which is good to reduce chip cost and improve the modulators compatibility in technology. Compared with other low-power low-voltage A/D modulators reported, this design has better FOM (Figure Of Merit).
2010, 32(2): 476-480.
doi: 10.3724/SP.J.1146.2008.01819
Abstract:
The ocean backscatter simulation is an important work for the ocean radar remote sensing application research and the design of the radar system for the ocean surveillance. Most of the ocean backscatter simulation models are based on the composite surface model, which involves the ocean wave spectrum and relax rate model. The numerous ocean spectrum and relax rate models are quite different from each other due to the different experimental and data fix methods. The different ocean spectrum and relax rate often lead to different ocean backscatter simulation results. In this paper, some typical ocean spectrum and relax rate models are used for the backscatter simulation and the results are compared with the experimental ocean scattering data. The comparison shows that the Romeiser spectrum model is better than other ocean spectrum models under the L-Ku band and 2-20m/s wind velocity, and the simulation results using different relax rate models are almost equivalent.
The ocean backscatter simulation is an important work for the ocean radar remote sensing application research and the design of the radar system for the ocean surveillance. Most of the ocean backscatter simulation models are based on the composite surface model, which involves the ocean wave spectrum and relax rate model. The numerous ocean spectrum and relax rate models are quite different from each other due to the different experimental and data fix methods. The different ocean spectrum and relax rate often lead to different ocean backscatter simulation results. In this paper, some typical ocean spectrum and relax rate models are used for the backscatter simulation and the results are compared with the experimental ocean scattering data. The comparison shows that the Romeiser spectrum model is better than other ocean spectrum models under the L-Ku band and 2-20m/s wind velocity, and the simulation results using different relax rate models are almost equivalent.
2010, 32(2): 481-484.
doi: 10.3724/SP.J.1146.2009.00705
Abstract:
An idea that an arbitrary transmit beampattern can be equal to a sum of the most basic beams is proposed. Based on the idea and using the Chebyshev weighting technique, the most basic beams are constructed with low side-lobes for a Multiple Input Multiple Output (MIMO) radar system with colocated antennas. The ratios of these beams are fast obtained by solving an effective linear programming. Compared with the existing Semidefinite Quadratic Programming (SQP) method, the designed transmit beampattern can achieve lower spatial side-lobes and cross-correlation. Furthermore, it is faster to design the transmit beampattern.
An idea that an arbitrary transmit beampattern can be equal to a sum of the most basic beams is proposed. Based on the idea and using the Chebyshev weighting technique, the most basic beams are constructed with low side-lobes for a Multiple Input Multiple Output (MIMO) radar system with colocated antennas. The ratios of these beams are fast obtained by solving an effective linear programming. Compared with the existing Semidefinite Quadratic Programming (SQP) method, the designed transmit beampattern can achieve lower spatial side-lobes and cross-correlation. Furthermore, it is faster to design the transmit beampattern.
2010, 32(2): 485-489.
doi: 10.3724/SP.J.1146.2008.01770
Abstract:
In the designation of the real-time imaging machine of Mini SAR, the radar return signal is sampled in the intermediate frequency, then Digital Down Converter(DDC) is used to realize quadrature demodulate, which can reduce system complexity and improve radars performance. The difficulty in the design of the DDC of Mini SAR is firstly given in this paper, i.e. the sampling frequency is as high as 2Gsps and the bandwidth is 900MHz, which leads large difficulty in real-time processing. The optimal architecture of DDC based on real design parameters is given in the next, with the emphasis on the difference of the parallel FIR filter and fast FIR filter. Then the implementation of the DDC module using parallel processing with optimized structure in FPGA is given, the resource usage, running speed and quantity noise influence are given. Finally, the result of Mini SAR is given, which confirms the validity of the design.
In the designation of the real-time imaging machine of Mini SAR, the radar return signal is sampled in the intermediate frequency, then Digital Down Converter(DDC) is used to realize quadrature demodulate, which can reduce system complexity and improve radars performance. The difficulty in the design of the DDC of Mini SAR is firstly given in this paper, i.e. the sampling frequency is as high as 2Gsps and the bandwidth is 900MHz, which leads large difficulty in real-time processing. The optimal architecture of DDC based on real design parameters is given in the next, with the emphasis on the difference of the parallel FIR filter and fast FIR filter. Then the implementation of the DDC module using parallel processing with optimized structure in FPGA is given, the resource usage, running speed and quantity noise influence are given. Finally, the result of Mini SAR is given, which confirms the validity of the design.
2010, 32(2): 490-494.
doi: 10.3724/SP.J.1146.2009.00025
Abstract:
Analog SAR echoes are usually sampled in both azimuth and range for digital processing, which will introduce error to point target peak measurements. This problem is analyzed in detail and the theoretical relationship between peak error and target location is given. For time-divided mode polarimetric SAR systems, azimuth sampling will also introduce relative error between different polarization data. A match-filtering method is proposed, which uses different time-delayed filtering functions for different polarization data, to produce the same effect of azimuth sampling on them. Simulation results prove its effectiveness in improving the magnitude and phase consistency.
Analog SAR echoes are usually sampled in both azimuth and range for digital processing, which will introduce error to point target peak measurements. This problem is analyzed in detail and the theoretical relationship between peak error and target location is given. For time-divided mode polarimetric SAR systems, azimuth sampling will also introduce relative error between different polarization data. A match-filtering method is proposed, which uses different time-delayed filtering functions for different polarization data, to produce the same effect of azimuth sampling on them. Simulation results prove its effectiveness in improving the magnitude and phase consistency.
2010, 32(2): 495-499.
doi: 10.3724/SP.J.1146.2009.00284
Abstract:
To solve the occlusion of multi touch, this paper presents a multi-touch locating method based on the collaboration of four cameras. It uses four cameras fixed at each corner of the frame to capture images synchronously, detects objects in each camera, builds lines directing the object according to epipolar geometry and 3D reconstruction, and finally calibrated with the four cameras to locate each object. The experiment result shows that this method can locate multi touch precisely even under occlusion and it is low cost, easy to install and transplant.
To solve the occlusion of multi touch, this paper presents a multi-touch locating method based on the collaboration of four cameras. It uses four cameras fixed at each corner of the frame to capture images synchronously, detects objects in each camera, builds lines directing the object according to epipolar geometry and 3D reconstruction, and finally calibrated with the four cameras to locate each object. The experiment result shows that this method can locate multi touch precisely even under occlusion and it is low cost, easy to install and transplant.
2010, 32(2): 500-503.
doi: 10.3724/SP.J.1146.2009.00070
Abstract:
MDS matrices and involution MDS matrices are widely used in block ciphers. This paper deals with those MDS matrices which are Hadamard matrices and Cauchy matrices simultaneously. Then the structure, the method of constructing and the count value of this kind of matrices are presented. By this, a new method for constructing MDS matrices is obtained. Additionally, this paper proves that a Cauchy-Hadamard type MDS matrix can be transformed into an involution Cauchy-Hadamard type MDS, and then proposes a new method to construct an involution Cauchy-Hadamard type MDS matrix from a Cauchy-Hadamard type MDS matrix.
MDS matrices and involution MDS matrices are widely used in block ciphers. This paper deals with those MDS matrices which are Hadamard matrices and Cauchy matrices simultaneously. Then the structure, the method of constructing and the count value of this kind of matrices are presented. By this, a new method for constructing MDS matrices is obtained. Additionally, this paper proves that a Cauchy-Hadamard type MDS matrix can be transformed into an involution Cauchy-Hadamard type MDS, and then proposes a new method to construct an involution Cauchy-Hadamard type MDS matrix from a Cauchy-Hadamard type MDS matrix.
2010, 32(2): 504-508.
doi: 10.3724/SP.J.1146.2009.00051
Abstract:
In this paper, an efficient hybrid sampling algorithm introducing the random walk method into the reversible jump Markov Chain Monte Carlo (RJMCMC) method is developed to jointly detect and estimate the wideband signals impinging on passive sensors, which combines the local sampling and the whole space sampling, and can get random number more obeying to target distribution in a shorter time. The method is proposed on the basis of Bayesian theory, and the statistical characteristic of the noise and signals. The accuracy and the validity of this method are well verified by the simulation.
In this paper, an efficient hybrid sampling algorithm introducing the random walk method into the reversible jump Markov Chain Monte Carlo (RJMCMC) method is developed to jointly detect and estimate the wideband signals impinging on passive sensors, which combines the local sampling and the whole space sampling, and can get random number more obeying to target distribution in a shorter time. The method is proposed on the basis of Bayesian theory, and the statistical characteristic of the noise and signals. The accuracy and the validity of this method are well verified by the simulation.
2010, 32(2): 470-475.
doi: 10.3724/SP.J.1146.2009.00497
Abstract:
The problems of how to reduce the sampling rate in the broadband analog signal digitization and how to compress effectively the large amount of data for storage are always concerned by researchers. The recent proposed Compressive Sampling or Compressive Sensing method to solve the said problems is introduced in this paper. The method, which employs non-adaptive linear projections that preserve the structure of the signal, can capture and represent the compressible signal at a rate significantly below Nyquist rate. This paper not only presents the key procedures of this theory but also lists a variety of applications and points out the questions to be studied.
The problems of how to reduce the sampling rate in the broadband analog signal digitization and how to compress effectively the large amount of data for storage are always concerned by researchers. The recent proposed Compressive Sampling or Compressive Sensing method to solve the said problems is introduced in this paper. The method, which employs non-adaptive linear projections that preserve the structure of the signal, can capture and represent the compressible signal at a rate significantly below Nyquist rate. This paper not only presents the key procedures of this theory but also lists a variety of applications and points out the questions to be studied.
