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2010 Vol. 32, No. 1
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2010, 32(1): 1-6.
doi: 10.3724/SP.J.1146.2008.01821
Abstract:
This paper focuses on the channel calibration for multi-channel Synthetic Aperture Radar (SAR) imagery. Incorporated with DBF processing, multi-channel SAR is promising in High-Resolution and Wide-Swath (HRWS) imaging. It coherently combines recorded multi-channel signals to overcome the spectrum ambiguity. However, the mismatch between channels and baseline errors should be compensated before the processing. In this paper, a novel calibration is proposed for multi-channel SAR HRWS imagery by making use of the orthogonality between signal subspace and noise subspace. The calibration is incorporated with the post-Doppler beam forming processing, which estimates the synthetic element error caused by nonideal factors. The real data experiment demonstrates the good performance of Doppler ambiguity suppression after our calibration. The results confirm the validity of the approach.
This paper focuses on the channel calibration for multi-channel Synthetic Aperture Radar (SAR) imagery. Incorporated with DBF processing, multi-channel SAR is promising in High-Resolution and Wide-Swath (HRWS) imaging. It coherently combines recorded multi-channel signals to overcome the spectrum ambiguity. However, the mismatch between channels and baseline errors should be compensated before the processing. In this paper, a novel calibration is proposed for multi-channel SAR HRWS imagery by making use of the orthogonality between signal subspace and noise subspace. The calibration is incorporated with the post-Doppler beam forming processing, which estimates the synthetic element error caused by nonideal factors. The real data experiment demonstrates the good performance of Doppler ambiguity suppression after our calibration. The results confirm the validity of the approach.
2010, 32(1): 7-11.
doi: 10.3724/SP.J.1146.2008.01809
Abstract:
MIMO radar with transmit diversity has the potential of high-resolution imaging, but the imaging results suffer from huge sidelobes. In order to analyze the imaging performance of MIMO radar, this paper establishes an imaging model firstly. The high-resolution ability of diversity is demonstrated from spatial spectral coverage, and the sidelobe performance of diversity image is analyzed in particular. Based on spectral extrapolation, a fusion imaging method for MIMO radar with transmit diversity is proposed. This method can achieve high-resolution images with good sidelobe performance. Finally, simulations are performed in order to validate the effectiveness of the proposed method.
MIMO radar with transmit diversity has the potential of high-resolution imaging, but the imaging results suffer from huge sidelobes. In order to analyze the imaging performance of MIMO radar, this paper establishes an imaging model firstly. The high-resolution ability of diversity is demonstrated from spatial spectral coverage, and the sidelobe performance of diversity image is analyzed in particular. Based on spectral extrapolation, a fusion imaging method for MIMO radar with transmit diversity is proposed. This method can achieve high-resolution images with good sidelobe performance. Finally, simulations are performed in order to validate the effectiveness of the proposed method.
2010, 32(1): 12-16.
doi: DOI: 10.3724/SP.J.1146.2009.00040
Abstract:
Considering the sparse structure of actual target space in GPR application, a novel 3D imaging method based on random aperture compressive sensing is proposed in this paper, which capable of reconstructing the target space from a few compressive sensing data obtained by random aperture measurements, and the imaging performance versus noise level and the effects of different measurement matrices are analyzed. The computer simulation results indicate that the proposed algorithm allow much fewer data, much shorter measurement time. And due to it is fully utilization of the sparse structure of interested target space, the method show much more robust and sparse image than time-domain standard back-projection method.
Considering the sparse structure of actual target space in GPR application, a novel 3D imaging method based on random aperture compressive sensing is proposed in this paper, which capable of reconstructing the target space from a few compressive sensing data obtained by random aperture measurements, and the imaging performance versus noise level and the effects of different measurement matrices are analyzed. The computer simulation results indicate that the proposed algorithm allow much fewer data, much shorter measurement time. And due to it is fully utilization of the sparse structure of interested target space, the method show much more robust and sparse image than time-domain standard back-projection method.
2010, 32(1): 17-21.
doi: 10.3724/SP.J.1146.2008.01509
Abstract:
Extraction of transmitted waveforms is an important step for MIMO radar. Based on Minimum Mean Square Error (MMSE) formulation, this paper presents a efficient approach for adaptive pulse compression filter of MIMO radar, in which weight coefficients of the filter for each individual range cell is adaptively estimated from the received signal in order to extract the transmitted waveforms better. Compared with the standard mached filter, the proposed method can suppress range sidelobe level of a transmitted waveform, and lower correlated level between different waveforms, and the algorithms tolerance to Doppler frequency is also determined. The computer simulation proves the efficiency of the algorithm.
Extraction of transmitted waveforms is an important step for MIMO radar. Based on Minimum Mean Square Error (MMSE) formulation, this paper presents a efficient approach for adaptive pulse compression filter of MIMO radar, in which weight coefficients of the filter for each individual range cell is adaptively estimated from the received signal in order to extract the transmitted waveforms better. Compared with the standard mached filter, the proposed method can suppress range sidelobe level of a transmitted waveform, and lower correlated level between different waveforms, and the algorithms tolerance to Doppler frequency is also determined. The computer simulation proves the efficiency of the algorithm.
2010, 32(1): 22-27.
doi: DOI: 10.3724/SP.J.1146.2008.01780
Abstract:
for the problem of electromechanical in the optimization design of reflector antennas with truss support structures, microscopic distortion of reflector surface is introduced in the formula of antennas far field patterns by phase difference, and the coupling formula of reflector antennas far field patterns is given. Results of verification experiment show that the coupling formula is accurate and efficient. By the coupling formula, electrical parameter could be included in the antenna structure optimization design. A mechatronic optimization design model of reflector antennas with truss support structures is developed ,which adopts antenna weight or gain as the optimization objective, and the structure strength and various electrical parameters as constraint conditions. So the main electrical parameters(include gain, side lobe, beam width and pointing accuracy) could be considered during structure optimization design, and the limitation of estimate gain only by surface precision is conquered. Finally the proposed optimization model is applied to an 8 meters antenna with good results.
for the problem of electromechanical in the optimization design of reflector antennas with truss support structures, microscopic distortion of reflector surface is introduced in the formula of antennas far field patterns by phase difference, and the coupling formula of reflector antennas far field patterns is given. Results of verification experiment show that the coupling formula is accurate and efficient. By the coupling formula, electrical parameter could be included in the antenna structure optimization design. A mechatronic optimization design model of reflector antennas with truss support structures is developed ,which adopts antenna weight or gain as the optimization objective, and the structure strength and various electrical parameters as constraint conditions. So the main electrical parameters(include gain, side lobe, beam width and pointing accuracy) could be considered during structure optimization design, and the limitation of estimate gain only by surface precision is conquered. Finally the proposed optimization model is applied to an 8 meters antenna with good results.
2010, 32(1): 28-31.
doi: 10.3724/SP.J.1146.2009.00500
Abstract:
This paper describes an airship borne SAR developed at the Institute of Electronics, Chinese Academy of Sciences. The airship borne SAR system features high resolution imaging capability of ground targets in the limited area. The function and architecture of the SAR are described in detail. An effective motion compensation method integrated IMU, DGPS and autofocus algorithm is proposed for the low speed airship platform. High quality images formed in the flight tests demonstrate the precision microwave imaging and measurement capacity provided by the airship borne SAR.
This paper describes an airship borne SAR developed at the Institute of Electronics, Chinese Academy of Sciences. The airship borne SAR system features high resolution imaging capability of ground targets in the limited area. The function and architecture of the SAR are described in detail. An effective motion compensation method integrated IMU, DGPS and autofocus algorithm is proposed for the low speed airship platform. High quality images formed in the flight tests demonstrate the precision microwave imaging and measurement capacity provided by the airship borne SAR.
2010, 32(1): 32-27.
doi: 10.3724/SP.J.1146.2008.01594
Abstract:
In this paper, based on the Dechirping technique, a new method of measuring relative delays among digital T/R modules for the wideband digital array utilizing wideband LFM pulses is proposed. To enhance radar systems flexibility and extensibility and reduce hardware costs, this method can be realized by software. By using the decimation and FFT algorithm, not only can the measurement method be easier to be implemented for computational efficiency and reduce data rate, but also good measurement precision and real-time performance are achieved, at the same time, all relative delays among multiple digital T/R modules are enabled to be acquired in one measurement process. The performance of the proposed method is analyzed from the theoretical angle and thus some optimal system parameters are determined. The simulation results show the effectiveness and efficiency of the proposed method.
In this paper, based on the Dechirping technique, a new method of measuring relative delays among digital T/R modules for the wideband digital array utilizing wideband LFM pulses is proposed. To enhance radar systems flexibility and extensibility and reduce hardware costs, this method can be realized by software. By using the decimation and FFT algorithm, not only can the measurement method be easier to be implemented for computational efficiency and reduce data rate, but also good measurement precision and real-time performance are achieved, at the same time, all relative delays among multiple digital T/R modules are enabled to be acquired in one measurement process. The performance of the proposed method is analyzed from the theoretical angle and thus some optimal system parameters are determined. The simulation results show the effectiveness and efficiency of the proposed method.
2010, 32(1): 38-42.
doi: 10.3724/SP.J.1146.2008.01536
Abstract:
Statistical properties of radar target echoes is researched on narrowband frequency diversity and spatial diversity MIMO radar, with a two-dimensional round shaped scatters model. The results show that target echo in any receiving channel follows a Gaussian distribution and the correlation coefficients between target echoes are functions of the Equivalent Frequency Interval (EFI) and the target size. Spatial diversity and frequency diversity radar are different in the definitions of EFI. Numerical experiment based on scatters model verifies the effectiveness of the correlation coefficients.
Statistical properties of radar target echoes is researched on narrowband frequency diversity and spatial diversity MIMO radar, with a two-dimensional round shaped scatters model. The results show that target echo in any receiving channel follows a Gaussian distribution and the correlation coefficients between target echoes are functions of the Equivalent Frequency Interval (EFI) and the target size. Spatial diversity and frequency diversity radar are different in the definitions of EFI. Numerical experiment based on scatters model verifies the effectiveness of the correlation coefficients.
2010, 32(1): 43-47.
doi: 10.3724/SP.J.1146.2009.00011
Abstract:
Based on the research of a differential filtering method retrieving composite shear from Doppler radar velocity data, considering the problems of this method, such as the number of edge detection points is too small, combined with the least squares advantage on Linear fitting and radar datas radial distribution character, this paper presents a method of least squares based on different fitting window. These two methods are compared and analyzed by using computing positioning accuracy method and so on. The method of least squares is better than the differential filtering method on positioning accuracy, identification ability, edge detection and so on. During the 2008 Beijing Olympic Games, by using the method of least squares, the radial velocity azimuth composite shear weather product provides some important information for the weather modification.
Based on the research of a differential filtering method retrieving composite shear from Doppler radar velocity data, considering the problems of this method, such as the number of edge detection points is too small, combined with the least squares advantage on Linear fitting and radar datas radial distribution character, this paper presents a method of least squares based on different fitting window. These two methods are compared and analyzed by using computing positioning accuracy method and so on. The method of least squares is better than the differential filtering method on positioning accuracy, identification ability, edge detection and so on. During the 2008 Beijing Olympic Games, by using the method of least squares, the radial velocity azimuth composite shear weather product provides some important information for the weather modification.
2010, 32(1): 48-53.
doi: 10.3724/SP.J.1146.2008.01470
Abstract:
The height measurement models considering earth curvature of INSAR mainly consist of two kinds- spaceborne interferometric SAR height measurement model and direct geocoding model. Spaceborne interferometric SAR height measurement model gets unambiguous interferometric phases through interferometric SAR, then calculates the terrain height by the spatial geometry considering earth curvature. Direct geocoding model obtains the three-dimensional coordinates using two slant range equations and one Doppler equation, based on the unambiguous interferometric phases. Because the methods getting the terrain height in the two models are different, it is difficult to compare the height measurement uncertainties of the models. Based on matrix theory, the explicit expressions of height uncertainty of direct gecoding model are presented. And it is proven that the height measurement uncertainty formulas of direct geocoding model are the same as that of spaceborne interferometric SAR height measurement model after introducing a new slane range plane coordinate system. Then it is proposed that these two models would lead to the same precision in height measurement. Finally, computer simulation is employed to validate the correctness of the theory analysis.
The height measurement models considering earth curvature of INSAR mainly consist of two kinds- spaceborne interferometric SAR height measurement model and direct geocoding model. Spaceborne interferometric SAR height measurement model gets unambiguous interferometric phases through interferometric SAR, then calculates the terrain height by the spatial geometry considering earth curvature. Direct geocoding model obtains the three-dimensional coordinates using two slant range equations and one Doppler equation, based on the unambiguous interferometric phases. Because the methods getting the terrain height in the two models are different, it is difficult to compare the height measurement uncertainties of the models. Based on matrix theory, the explicit expressions of height uncertainty of direct gecoding model are presented. And it is proven that the height measurement uncertainty formulas of direct geocoding model are the same as that of spaceborne interferometric SAR height measurement model after introducing a new slane range plane coordinate system. Then it is proposed that these two models would lead to the same precision in height measurement. Finally, computer simulation is employed to validate the correctness of the theory analysis.
2010, 32(1): 54-61.
doi: 10.3724/SP.J.1146.2008.00980
Abstract:
This paper studies the multifractal correlation characteristic of sea clutter and its application to the low-observable target detection within sea clutter. Multifractal correlation, which studies the spatial correlation of two points with different singularity intensity, is a generalization of multifractal single point statistic. First, the paper introduces the multifractal correlation theory and the computation of the multifractal correlation spectrum. Then the multifractal correlation spectrum is used as a character to analyze the similarity degree to match board. In fact, target detection can be regarded as binary-classification, therefore the SVM (Support Vector Machine) is adopted for target detection. Finally, real sea clutter in different bands, polarizations and resolutions is used to verify the method proposed. The results show that the method has good performance of low-observable target detection.
This paper studies the multifractal correlation characteristic of sea clutter and its application to the low-observable target detection within sea clutter. Multifractal correlation, which studies the spatial correlation of two points with different singularity intensity, is a generalization of multifractal single point statistic. First, the paper introduces the multifractal correlation theory and the computation of the multifractal correlation spectrum. Then the multifractal correlation spectrum is used as a character to analyze the similarity degree to match board. In fact, target detection can be regarded as binary-classification, therefore the SVM (Support Vector Machine) is adopted for target detection. Finally, real sea clutter in different bands, polarizations and resolutions is used to verify the method proposed. The results show that the method has good performance of low-observable target detection.
2010, 32(1): 62-68.
doi: 10.3724/SP.J.1146.2008.01561
Abstract:
A method of ground moving target detection based on subband and subaperture ATI image series is proposed. It exploits the wideband, large beamwidth and low frequency characteristics of UWB SAR to generate a series of subband and subaperture ATI images. These images corresponding to different centre frequencies and angle-views are combinded to detect a moving target and estimate its parameters. The proposed method in the paper has improvements over traditional ATI method. For detection, it removes blind velocity and can detect the moving target not only with range velocity, but also with azimuth velocity. Besides, it can estimate the unwrapped range velocity and azimuth velocity as well. The experiment based on UWB SAR half-real echo validates the method.
A method of ground moving target detection based on subband and subaperture ATI image series is proposed. It exploits the wideband, large beamwidth and low frequency characteristics of UWB SAR to generate a series of subband and subaperture ATI images. These images corresponding to different centre frequencies and angle-views are combinded to detect a moving target and estimate its parameters. The proposed method in the paper has improvements over traditional ATI method. For detection, it removes blind velocity and can detect the moving target not only with range velocity, but also with azimuth velocity. Besides, it can estimate the unwrapped range velocity and azimuth velocity as well. The experiment based on UWB SAR half-real echo validates the method.
2010, 32(1): 69-74.
doi: 10.3724/SP.J.1146.2008.01636
Abstract:
Repeater jamming is an effective means to Synthetic Aperture Radar(SAR). In this paper, the principle of the SAR repeater jamming is introduced, and the positions and imaging quality of the illusory targets are also discussed. Meanwhile, considering the signal processing time in the practical engineering, the feasibility of the received signals delay repeating is also studied. Simulation result confirms the conclusions derived from above, and a practical use of the repeater jamming is introduced at last.
Repeater jamming is an effective means to Synthetic Aperture Radar(SAR). In this paper, the principle of the SAR repeater jamming is introduced, and the positions and imaging quality of the illusory targets are also discussed. Meanwhile, considering the signal processing time in the practical engineering, the feasibility of the received signals delay repeating is also studied. Simulation result confirms the conclusions derived from above, and a practical use of the repeater jamming is introduced at last.
2010, 32(1): 75-79.
doi: 10.3724/SP.J.1146.2009.00121
Abstract:
Bi-SAR system is characterized by strong anti-interference capability, this paper analyzes the deceptive jamming to the Bi-SAR with non-precision positioning receiver. The model of deceptive jamming against Bi-SAR is given, then the defocus issue of deceptive jamming is studied. Through theoretical analysis, it can ascertain the scope of the permission settings and generate the deceptive jamming signals under the condition of tolerable focus. Simulation results verify the correctness of the theory analysis.
Bi-SAR system is characterized by strong anti-interference capability, this paper analyzes the deceptive jamming to the Bi-SAR with non-precision positioning receiver. The model of deceptive jamming against Bi-SAR is given, then the defocus issue of deceptive jamming is studied. Through theoretical analysis, it can ascertain the scope of the permission settings and generate the deceptive jamming signals under the condition of tolerable focus. Simulation results verify the correctness of the theory analysis.
2010, 32(1): 80-85.
doi: 10.3724/SP.J.1146.2009.00015
Abstract:
This paper presents a Time-Delay Recurrent Neural Network (TDRNN) for exo-atmospheric ballistic space infrared target discrimination. The TDRNN employs adaptive time delays and recurrences where the adaptive time delays make the network choose the optimal values of time delays for the temporal location of important information in the input sequence, and the recurrences enable the network to have dynamic discrimination function. The IR radiation data of space target considering the sensor effect is simulated, taking into account the synthetic factors of heat parameter and motion, the space environment radiation and the sensor effect. The target discrimination experiment is developed, based on dynamic IR radiation simulated data of four typical ballistic space target. The simulation results show that TDRNN have better discrimination ability.
This paper presents a Time-Delay Recurrent Neural Network (TDRNN) for exo-atmospheric ballistic space infrared target discrimination. The TDRNN employs adaptive time delays and recurrences where the adaptive time delays make the network choose the optimal values of time delays for the temporal location of important information in the input sequence, and the recurrences enable the network to have dynamic discrimination function. The IR radiation data of space target considering the sensor effect is simulated, taking into account the synthetic factors of heat parameter and motion, the space environment radiation and the sensor effect. The target discrimination experiment is developed, based on dynamic IR radiation simulated data of four typical ballistic space target. The simulation results show that TDRNN have better discrimination ability.
2010, 32(1): 86-91.
doi: 10.3724/SP.J.1146.2008.01774
Abstract:
Concerning the distortion, robustness and decoding error probability, this paper analyses the performance of Distortion-Compensated Quantization Index Modulation (DC-QIM) watermarking scheme with a scaling factor of step. On the assumption that quantization is high resolution, a formula of decoding error probability for DC-QIM watermarking scheme is derived under the Additive White Gaussian Noise (AWGN) channel, and a distortion-robustness function is defined as a criterion characterizing the tradeoff between distortion and the robustness. In the experiment, several audio sections are selected as the hosts and their third lever wavelet detail coefficients are quantified according to watermark bit series. In term of the distortion-robustness and decoding error probability, which of different DC-QIM schemes are compared, simulation result and experimental value are in accord with predictive one when step is on the small side.
Concerning the distortion, robustness and decoding error probability, this paper analyses the performance of Distortion-Compensated Quantization Index Modulation (DC-QIM) watermarking scheme with a scaling factor of step. On the assumption that quantization is high resolution, a formula of decoding error probability for DC-QIM watermarking scheme is derived under the Additive White Gaussian Noise (AWGN) channel, and a distortion-robustness function is defined as a criterion characterizing the tradeoff between distortion and the robustness. In the experiment, several audio sections are selected as the hosts and their third lever wavelet detail coefficients are quantified according to watermark bit series. In term of the distortion-robustness and decoding error probability, which of different DC-QIM schemes are compared, simulation result and experimental value are in accord with predictive one when step is on the small side.
2010, 32(1): 92-97.
doi: 10.3724/SP.J.1146.2008.01698
Abstract:
To deal with the problem of premature convergence of the traditional K-means algorithm, a novel K-means cluster method based on the enhanced Particle Swarm Optimization(PSO) algorithm is presented. In this approach, the stochastic mutation operation is introduced into the PSO evolution, which reinforces the exploitation of global optimum of the PSO algorithm. In order to avoid the premature convergence and speed up the convergence, traditional K-means algorithm is used to explore the local search space more efficiently dynamically according to the variation of the particle swarms fitness variance. Comparison of the performance of the proposed approach with the cluster method based on K-means, traditional PSO algorithm and other PSO-K-means algorithm is experimented. The experimental results show the proposed method can not only effectively solve the premature convergence problem, but also significantly speed up the convergence.
To deal with the problem of premature convergence of the traditional K-means algorithm, a novel K-means cluster method based on the enhanced Particle Swarm Optimization(PSO) algorithm is presented. In this approach, the stochastic mutation operation is introduced into the PSO evolution, which reinforces the exploitation of global optimum of the PSO algorithm. In order to avoid the premature convergence and speed up the convergence, traditional K-means algorithm is used to explore the local search space more efficiently dynamically according to the variation of the particle swarms fitness variance. Comparison of the performance of the proposed approach with the cluster method based on K-means, traditional PSO algorithm and other PSO-K-means algorithm is experimented. The experimental results show the proposed method can not only effectively solve the premature convergence problem, but also significantly speed up the convergence.
2010, 32(1): 98-101.
doi: 10.3724/SP.J.1146.2008.00661
Abstract:
In this paper, a new DOA and angular spread estimation algorithm for incoherently distributed source is proposed. According to covariance matrixs structure character of the spatial frequency model of single incoherently distributed source, the covariance matrix can be separated into two matrixes rebuilt by phase information and amplitude information, respectively. Averaging over the main diagonal and sub-diagonals elements of the matrixes, two averaged vectors containing phase information and amplitude information could be obtained. Using least square fitting, the DOA could be estimated from the phase information, the angular spread could be estimated by substituting the estimated DOA into the amplitude information, and thus the decoupled estimation of DOA and angular spread are realized for incoherently distributed source. Numerical examples illustrate the performance of the method.
In this paper, a new DOA and angular spread estimation algorithm for incoherently distributed source is proposed. According to covariance matrixs structure character of the spatial frequency model of single incoherently distributed source, the covariance matrix can be separated into two matrixes rebuilt by phase information and amplitude information, respectively. Averaging over the main diagonal and sub-diagonals elements of the matrixes, two averaged vectors containing phase information and amplitude information could be obtained. Using least square fitting, the DOA could be estimated from the phase information, the angular spread could be estimated by substituting the estimated DOA into the amplitude information, and thus the decoupled estimation of DOA and angular spread are realized for incoherently distributed source. Numerical examples illustrate the performance of the method.
2010, 32(1): 102-106.
doi: 10.3724/SP.J.1146.2008.01769
Abstract:
SNR (Signal-to-Noise Ratio) is an important parameter in communication signal processing and many algorithms need this information to obtain optimal performance. Firstly, signal power is calculated by determining spectral domain of Intermediate Frequency (IF) communication signal. Then, SNR is estimated according to its definition. Therefore, a fast blind SNR estimation algorithm is put forward for IF communication signals without any prior knowledge. Computer simulations are performed for the commonly used linear modulated communication signals, such as BPSK, QPSK, and 16QAM. Simulation results indicate that the algorithm is robust with estimated bias and root mean square error almost within 0.5dB when data length is 4096 and true SNR varies in the range from -5dB to 25dB. Compared with eigenvalue decomposition method, the proposed algorithm can achieve accurate estimation with low computational complexity and wide dynamic range.
SNR (Signal-to-Noise Ratio) is an important parameter in communication signal processing and many algorithms need this information to obtain optimal performance. Firstly, signal power is calculated by determining spectral domain of Intermediate Frequency (IF) communication signal. Then, SNR is estimated according to its definition. Therefore, a fast blind SNR estimation algorithm is put forward for IF communication signals without any prior knowledge. Computer simulations are performed for the commonly used linear modulated communication signals, such as BPSK, QPSK, and 16QAM. Simulation results indicate that the algorithm is robust with estimated bias and root mean square error almost within 0.5dB when data length is 4096 and true SNR varies in the range from -5dB to 25dB. Compared with eigenvalue decomposition method, the proposed algorithm can achieve accurate estimation with low computational complexity and wide dynamic range.
2010, 32(1): 107-111.
doi: 10.3724/SP.J.1146.2008.01768
Abstract:
In actual environments the performance of speech recognition system may be degraded significantly because of the mismatch between the training and testing conditions. Model adaptation is an efficient approach that could reduce this mismatch, which adapts model parameters to new conditions by some adaptation data. In this paper, a new model adaptation using vector Taylor series is presented, which adapts the mean vector and covariance matrix of hidden Markov model. The experimental results show that the proposed algorithm is more effective than MLLR and the feature compensation algorithm based on vector Taylor series in various environments, especially in low signal-to-noise ratio environments.
In actual environments the performance of speech recognition system may be degraded significantly because of the mismatch between the training and testing conditions. Model adaptation is an efficient approach that could reduce this mismatch, which adapts model parameters to new conditions by some adaptation data. In this paper, a new model adaptation using vector Taylor series is presented, which adapts the mean vector and covariance matrix of hidden Markov model. The experimental results show that the proposed algorithm is more effective than MLLR and the feature compensation algorithm based on vector Taylor series in various environments, especially in low signal-to-noise ratio environments.
2010, 32(1): 112-116.
doi: 10.3724/SP.J.1146.2008.01810
Abstract:
In coding theory, it is important to study the distance distribution of codewords. The Homogeneous weight over ring R=F2+uF2++uk-1F2 is defined. Hamming distances and Homogeneous distances of (1+u)-constacyclic codes of length 2S over the ring R are studied. By means of the theory of finite rings, the structure of (1+u)-constacyclic codes of length 2S over R is also obtained. Especially, the structure and the size of cyclic self-dual codes over the ring are also given. Then, using the structure of such constacyclic codes, the distributions of the Hamming distances and Homogeneous distances of such constacyclic codes are determined.
In coding theory, it is important to study the distance distribution of codewords. The Homogeneous weight over ring R=F2+uF2++uk-1F2 is defined. Hamming distances and Homogeneous distances of (1+u)-constacyclic codes of length 2S over the ring R are studied. By means of the theory of finite rings, the structure of (1+u)-constacyclic codes of length 2S over R is also obtained. Especially, the structure and the size of cyclic self-dual codes over the ring are also given. Then, using the structure of such constacyclic codes, the distributions of the Hamming distances and Homogeneous distances of such constacyclic codes are determined.
2010, 32(1): 117-122.
doi: 10.3724/SP.J.1146.2008.01664
Abstract:
This paper addresses the video distortion of intra-frame coding in multigeneration, which is introduced by the current clip operation and intra-frame prediction. In order to implement the Re-Loss-Free (RLF) intra-frame coding in modified H.264, a novel optimal clipping algorithm based on Integer Linear Programming (ILP) and its improved algorithm are proposed. Furthermore, the cost function of intra-frame prediction is improved to guarantee later encoder the same prediction values with the former. Experimental results show that the ILP-based intra-frame coding method completely eliminates the video degradation and achieves superior performance in comparison with current intra-frame coding method in H.264.
This paper addresses the video distortion of intra-frame coding in multigeneration, which is introduced by the current clip operation and intra-frame prediction. In order to implement the Re-Loss-Free (RLF) intra-frame coding in modified H.264, a novel optimal clipping algorithm based on Integer Linear Programming (ILP) and its improved algorithm are proposed. Furthermore, the cost function of intra-frame prediction is improved to guarantee later encoder the same prediction values with the former. Experimental results show that the ILP-based intra-frame coding method completely eliminates the video degradation and achieves superior performance in comparison with current intra-frame coding method in H.264.
2010, 32(1): 123-128.
doi: 10.3724/SP.J.1146.2008.01667
Abstract:
Based on the Variational Bayes (VB) method, a novel low complexity semi-blind Bayesian iterative receiver with joint signal detection and channel tracking is proposed for MIMO-OFDM systems over time-varying multi-path channel. Using the VB Expectation-Maximization (VBEM) algorithm, a Recursive VBEM (RVBEM) channel tracking algorithm is derived for the newly proposed receiver. Since the RVBEM algorithm requires computation of matrix inversion, a Time domain and Frequency domain combined Low Complexity RVBEM (TF-LCRVBEM) algorithm is further proposed to reduce complexity. It is demonstrated that the TF-LCRVBEM algorithm completely avoids matrix inversion and obtains linear complexity by making some reasonable approximations. The simulation results show that the proposed receiver not only outperforms the conventional receiver, but also can achieve near optimal performance.
Based on the Variational Bayes (VB) method, a novel low complexity semi-blind Bayesian iterative receiver with joint signal detection and channel tracking is proposed for MIMO-OFDM systems over time-varying multi-path channel. Using the VB Expectation-Maximization (VBEM) algorithm, a Recursive VBEM (RVBEM) channel tracking algorithm is derived for the newly proposed receiver. Since the RVBEM algorithm requires computation of matrix inversion, a Time domain and Frequency domain combined Low Complexity RVBEM (TF-LCRVBEM) algorithm is further proposed to reduce complexity. It is demonstrated that the TF-LCRVBEM algorithm completely avoids matrix inversion and obtains linear complexity by making some reasonable approximations. The simulation results show that the proposed receiver not only outperforms the conventional receiver, but also can achieve near optimal performance.
2010, 32(1): 129-134.
doi: 10.3724/SP.J.1146.2009.00517
Abstract:
In this paper, the DET (Double Eigenvalue Threshold) cooperative spectrum sensing algorithm is proposed through analyzing maximum eigenvalue distribution of the covariance matrix of the received signals by means of random matrix theory. DET cooperative sensing algorithm needs neither the prior acknowledge of the signal transmitted from primary user, nor the noise power in advance. Simulation results show that the proposed scheme can gain higher sensing performance with a few of secondary users and is more robust to the noise uncertainty compared with the conventional sensing schemes.
In this paper, the DET (Double Eigenvalue Threshold) cooperative spectrum sensing algorithm is proposed through analyzing maximum eigenvalue distribution of the covariance matrix of the received signals by means of random matrix theory. DET cooperative sensing algorithm needs neither the prior acknowledge of the signal transmitted from primary user, nor the noise power in advance. Simulation results show that the proposed scheme can gain higher sensing performance with a few of secondary users and is more robust to the noise uncertainty compared with the conventional sensing schemes.
2010, 32(1): 135-140.
doi: 10.3724/SP.J.1146.2008.01576
Abstract:
Dynamic subchannel allocation based MIMO-OFDM beamforming system outperforms conventional MIMO-OFDM beamforming system with considerable gain. Unfortunately, the imperfect channel state information, which is due to processing or feedback time delay, will be used by the transmitter to transmit data symbols. The resulted inter-streams interference will degrade the system performance significantly. In this paper, an improved detection scheme is proposed to combat effectively with this interference according to the analysis of the effect due to delay. By constructing equivalent MIMO system model, the inter-streams interference is suppressed though MIMO detection algorithms. Furthermore, eigenvalue decomposition of equivalent MIMO channel is applied to whiten the noise so that equivalent Gaussian channel model can be obtained to compute the log-likelihood ratio of coded bits. Simulation results show the proposed detection scheme outperforms conventional scheme with a gain of 2.5~4 dB.
Dynamic subchannel allocation based MIMO-OFDM beamforming system outperforms conventional MIMO-OFDM beamforming system with considerable gain. Unfortunately, the imperfect channel state information, which is due to processing or feedback time delay, will be used by the transmitter to transmit data symbols. The resulted inter-streams interference will degrade the system performance significantly. In this paper, an improved detection scheme is proposed to combat effectively with this interference according to the analysis of the effect due to delay. By constructing equivalent MIMO system model, the inter-streams interference is suppressed though MIMO detection algorithms. Furthermore, eigenvalue decomposition of equivalent MIMO channel is applied to whiten the noise so that equivalent Gaussian channel model can be obtained to compute the log-likelihood ratio of coded bits. Simulation results show the proposed detection scheme outperforms conventional scheme with a gain of 2.5~4 dB.
2010, 32(1): 141-145.
doi: 10.3724/SP.J.1146.2008.01776
Abstract:
Considering the dynamic nature in Cognitive Radio (CR) system, differential game theory is adopted in power control for CR system and a novel model of noncooperative differential game for power control is presented. Then a distributed noncooperative power control algorithm based on differential game is proposed in this paper. The proposed algorithm achieves the distributed dynamic power control under the condition that the requirements, including the average power threshold and QoS of secondary users, are guaranteed. Furthermore, an analytical solution to feedback Nash equilibrium is obtained. Simulation results show that the proposed algorithm can regulate the transmitted power of secondary users effectively to enhance the total throughput, and the performance of CR system is thereby improved.
Considering the dynamic nature in Cognitive Radio (CR) system, differential game theory is adopted in power control for CR system and a novel model of noncooperative differential game for power control is presented. Then a distributed noncooperative power control algorithm based on differential game is proposed in this paper. The proposed algorithm achieves the distributed dynamic power control under the condition that the requirements, including the average power threshold and QoS of secondary users, are guaranteed. Furthermore, an analytical solution to feedback Nash equilibrium is obtained. Simulation results show that the proposed algorithm can regulate the transmitted power of secondary users effectively to enhance the total throughput, and the performance of CR system is thereby improved.
2010, 32(1): 146-150.
doi: 10.3724/SP.J.1146.2008.01815
Abstract:
The block-modulated based OFDM algorithm is presented in MIMO-OFDM system to reduce the cost that is taken up by the Cyclic Prefix (CP). At each transmitter antenna, P OFDM data blocks are modulated jointly and framed together to use one single CP, and after the received frame at each receiver antenna is decomposed, P received blocks are obtained without inter-block interference where the pth block is equal to the sum of the pth OFDM data block in each transmitter passing through the MIMO channel. While the transmission mode and performance of the scheme proposed are equivalent to that of conventional MIMO-OFDM system, the band efficiency is improved dramatically.
The block-modulated based OFDM algorithm is presented in MIMO-OFDM system to reduce the cost that is taken up by the Cyclic Prefix (CP). At each transmitter antenna, P OFDM data blocks are modulated jointly and framed together to use one single CP, and after the received frame at each receiver antenna is decomposed, P received blocks are obtained without inter-block interference where the pth block is equal to the sum of the pth OFDM data block in each transmitter passing through the MIMO channel. While the transmission mode and performance of the scheme proposed are equivalent to that of conventional MIMO-OFDM system, the band efficiency is improved dramatically.
2010, 32(1): 151-156.
doi: 10.3724/SP.J.1146.2009.00050
Abstract:
In this paper, theoretical analysis and simulations are performed on the performance of synchronous shortwave Differential Frequency Hopping (DFH) systems in the Multiple-Access (MA) communications. Single-user detection and multi-user detection are both considered. For single-user detection, Bit Error Rate (BER) upperbounds are derived and verified via simulation, both in the noiseless case and noise case. Results show that when the number of users is 2, the BER is 10-6 for the noiseless case. Furthermore, MA performance can be significantly improved if exact Jammer State Information (JSI) is available. Therefore, an iterative multi-user detection algorithm is proposed. In the iteration process, JSI of each available frequency is estimated and used to perform maximum likelihood detection for each user. Simulation results show that significant performance improvement is obtained relative to single-user detection.
In this paper, theoretical analysis and simulations are performed on the performance of synchronous shortwave Differential Frequency Hopping (DFH) systems in the Multiple-Access (MA) communications. Single-user detection and multi-user detection are both considered. For single-user detection, Bit Error Rate (BER) upperbounds are derived and verified via simulation, both in the noiseless case and noise case. Results show that when the number of users is 2, the BER is 10-6 for the noiseless case. Furthermore, MA performance can be significantly improved if exact Jammer State Information (JSI) is available. Therefore, an iterative multi-user detection algorithm is proposed. In the iteration process, JSI of each available frequency is estimated and used to perform maximum likelihood detection for each user. Simulation results show that significant performance improvement is obtained relative to single-user detection.
2010, 32(1): 157-161.
doi: 10.3724/SP.J.1146.2008.01846
Abstract:
3D cipher is a new block cipher proposed in CANS 2008. It is different from all known block cipher as it uses the three dimension structure. According to the structure properties of 3D cipher, a new 5.25-round and a new 6.25-round square distinguishers are presented, and the square attacks on reduced- round 3D are improved. Attacking results demonstrate that 6-round attack is better than the known square attacks in data complexity and time complexity. Moreover, these two new distinguishers can be applied to 7/8/9-round 3D cipher.
3D cipher is a new block cipher proposed in CANS 2008. It is different from all known block cipher as it uses the three dimension structure. According to the structure properties of 3D cipher, a new 5.25-round and a new 6.25-round square distinguishers are presented, and the square attacks on reduced- round 3D are improved. Attacking results demonstrate that 6-round attack is better than the known square attacks in data complexity and time complexity. Moreover, these two new distinguishers can be applied to 7/8/9-round 3D cipher.
2010, 32(1): 162-165.
doi: 10.3724/SP.J.1146.2009.00030
Abstract:
Dividing the cover image into matrix blocks, using the pixels in the matrix blocks repeatedly, this paper constructs a new double-layered steganographic algorithm based on Hamming code and wet paper code. For each matrix block, the secret message is first embedded by using Hamming code in rows. Then according to whether the previous embedding result is influenced or whether 3 changes are needed when embedding message in columns, the notation of dry and wet is introduced. Finally wet paper code is used for second embedding. The proposed setganographic algorithm can obtain better performance than PPC and F5 algorithm for 0.1-0.8bpp of embedding rate.
Dividing the cover image into matrix blocks, using the pixels in the matrix blocks repeatedly, this paper constructs a new double-layered steganographic algorithm based on Hamming code and wet paper code. For each matrix block, the secret message is first embedded by using Hamming code in rows. Then according to whether the previous embedding result is influenced or whether 3 changes are needed when embedding message in columns, the notation of dry and wet is introduced. Finally wet paper code is used for second embedding. The proposed setganographic algorithm can obtain better performance than PPC and F5 algorithm for 0.1-0.8bpp of embedding rate.
2010, 32(1): 166-171.
doi: 10.3724/SP.J.1146.2008.01800
Abstract:
A multi-sensor feature fusion algorithm based on improved Local Discriminant Bases (LDB) and Binary Particle Swarm Optimization (BPSO) is proposed in this paper to satisfy the requirement of application on classification of ground targets in wireless sensor networks. LDB is improved by a new discriminant measure using relative differential entropy based on probability density estimation and used to extract the characteristic frequency band of signals. Then an improved and a new BPSO are used for feature fusion respectively. Based on real acoustic and seismic signals of ground targets, experiment results indicate that this method can decrease the classifier number needed, reduce the dimension of features, and improve the performance of classification at a certain extent, so it is practically valuable for application.
A multi-sensor feature fusion algorithm based on improved Local Discriminant Bases (LDB) and Binary Particle Swarm Optimization (BPSO) is proposed in this paper to satisfy the requirement of application on classification of ground targets in wireless sensor networks. LDB is improved by a new discriminant measure using relative differential entropy based on probability density estimation and used to extract the characteristic frequency band of signals. Then an improved and a new BPSO are used for feature fusion respectively. Based on real acoustic and seismic signals of ground targets, experiment results indicate that this method can decrease the classifier number needed, reduce the dimension of features, and improve the performance of classification at a certain extent, so it is practically valuable for application.
2010, 32(1): 172-177.
doi: 10.3724/SP.J.1146.2008.01783
Abstract:
This paper presents a new physical network topology discovery algorithm. The tree form is applied to describe the connections between switches. Based on this theory, the topology discovery is completed by using spanning tree set to deduce tree change, and the algorithm referring to a typical connection relationship between switches is derived. Theoretical analysis and practical application indicate that the proposed topology discovery algorithm is advanced in efficiency, accuracy and effectiveness.
This paper presents a new physical network topology discovery algorithm. The tree form is applied to describe the connections between switches. Based on this theory, the topology discovery is completed by using spanning tree set to deduce tree change, and the algorithm referring to a typical connection relationship between switches is derived. Theoretical analysis and practical application indicate that the proposed topology discovery algorithm is advanced in efficiency, accuracy and effectiveness.
2010, 32(1): 178-182.
doi: 10.3724/SP.J.1146.2008.01516
Abstract:
Due to heterogeneous network environment with the characteristics of uncertainty for unlicensed users, based on the theory of Partially Observable Markov Decision Process (POMDP) model, a novel multi-radio multi-channel channel state prediction algorithm is proposed using spectrum sensing techniques of cognitive radio. By the analysis of the channel state historical information, the initial distribution of the belief state and transition probability is derivated and the channel with optimal reward is selected for unlicensed user to improve the spectrum utilization. The simulation results demonstrate that the proposed algorithm has better performance than classical algorithms.
Due to heterogeneous network environment with the characteristics of uncertainty for unlicensed users, based on the theory of Partially Observable Markov Decision Process (POMDP) model, a novel multi-radio multi-channel channel state prediction algorithm is proposed using spectrum sensing techniques of cognitive radio. By the analysis of the channel state historical information, the initial distribution of the belief state and transition probability is derivated and the channel with optimal reward is selected for unlicensed user to improve the spectrum utilization. The simulation results demonstrate that the proposed algorithm has better performance than classical algorithms.
2010, 32(1): 189-194.
doi: 10.3724/SP.J.1146.2009.00694
Abstract:
The Heterogeneous Wireless Sensor Networks (HWSN), which is more univeral, shows a lack of the study for coverage force sections. Therefore a novel localized method for analyzing the distribution of coverage forcethe Coverage Force Algorithm (CFA) is presented. Depending on sensors own sensing abilities in HWSN, CFA can obtain the General Voronoi diagram and achieve section of coverage force for each node. Fortunately, simulations confirm that the CFA is able to solve the problem of analyzing coverage performance in HWSN. Compared to the traditional Voronoi diagram, the propsed algorithm shares the localized and general feature.
The Heterogeneous Wireless Sensor Networks (HWSN), which is more univeral, shows a lack of the study for coverage force sections. Therefore a novel localized method for analyzing the distribution of coverage forcethe Coverage Force Algorithm (CFA) is presented. Depending on sensors own sensing abilities in HWSN, CFA can obtain the General Voronoi diagram and achieve section of coverage force for each node. Fortunately, simulations confirm that the CFA is able to solve the problem of analyzing coverage performance in HWSN. Compared to the traditional Voronoi diagram, the propsed algorithm shares the localized and general feature.
2010, 32(1): 195-198.
doi: 10.3724/SP.J.1146.2008.01703
Abstract:
To reduce the faults caused by thickness resonance in the traditional numerical analysis method, and achieve the coexistence between the high analysis precision and the high efficiency of the Left-Hand Materials(LHMs), the neural network model based on the back propagation multi-layer forward feed neural network is built between electromagnetism characteristic parameters and the dielectric sensitive structural parameters, which is used to analyze the basic Left-Hand Materials structural. The experimental results show that the analysis time is 145.535648 seconds and the training mean square error is 0.00020679 while adopting the scaled conjugate gradient method. The results achieved in the paper are coincident with these ones by the full wave method, satisfying the engineering demand. It effectively overcomes the instability while extracting the parameters in re-forecasting process, and provides a method with rapid and precise for the structure of Left-Handed Materials.
To reduce the faults caused by thickness resonance in the traditional numerical analysis method, and achieve the coexistence between the high analysis precision and the high efficiency of the Left-Hand Materials(LHMs), the neural network model based on the back propagation multi-layer forward feed neural network is built between electromagnetism characteristic parameters and the dielectric sensitive structural parameters, which is used to analyze the basic Left-Hand Materials structural. The experimental results show that the analysis time is 145.535648 seconds and the training mean square error is 0.00020679 while adopting the scaled conjugate gradient method. The results achieved in the paper are coincident with these ones by the full wave method, satisfying the engineering demand. It effectively overcomes the instability while extracting the parameters in re-forecasting process, and provides a method with rapid and precise for the structure of Left-Handed Materials.
2010, 32(1): 199-202.
doi: 10.3724/SP.J.1146.2009.00046
Abstract:
A novel stop-band FSS structure which is used to reduce the RCS of antenna is presented in this paper. For incident waves, the proposed structure has narrow stopband and wide pass band. Hence, the conventional metallic ground plane can be replaced with the proposed FSS to reduce the RCS of antenna. Simulated and experimental results show that the RCS of antenna is reduced considerably with the proposed FSS ground plane.
A novel stop-band FSS structure which is used to reduce the RCS of antenna is presented in this paper. For incident waves, the proposed structure has narrow stopband and wide pass band. Hence, the conventional metallic ground plane can be replaced with the proposed FSS to reduce the RCS of antenna. Simulated and experimental results show that the RCS of antenna is reduced considerably with the proposed FSS ground plane.
2010, 32(1): 203-209.
doi: 10.3724/SP.J.1146.2008.01763
Abstract:
Readout circuit is a key factor determining the performance of MEMS gyroscope system, being at the forefront of the signal loop. This paper presents a low-noise readout circuit for a bulk micromachined tuning fork gyroscope. Using the chopper technique, the circuit can improve the resolution and dynamic range by canceling 1/f noise and offset of the amplifier, and mismatch between reference voltages. Theory predicting the resolution of the readout circuit is given which is based on noise charge transfer method. In order to simulate the response of the circuit with the vibrating gyroscope, a simplified time-varying capacitor model is also proposed. The chip measures 22.5 mm2 in a standard 0.35 m 2P4M CMOS process. Chip tests with the MEMS gyroscope prove the validity of the concepts proposed and show that the readout circuit achieves a resolution of 4 aF with 94 dB dynamic range from a single 5 V supply.
Readout circuit is a key factor determining the performance of MEMS gyroscope system, being at the forefront of the signal loop. This paper presents a low-noise readout circuit for a bulk micromachined tuning fork gyroscope. Using the chopper technique, the circuit can improve the resolution and dynamic range by canceling 1/f noise and offset of the amplifier, and mismatch between reference voltages. Theory predicting the resolution of the readout circuit is given which is based on noise charge transfer method. In order to simulate the response of the circuit with the vibrating gyroscope, a simplified time-varying capacitor model is also proposed. The chip measures 22.5 mm2 in a standard 0.35 m 2P4M CMOS process. Chip tests with the MEMS gyroscope prove the validity of the concepts proposed and show that the readout circuit achieves a resolution of 4 aF with 94 dB dynamic range from a single 5 V supply.
2010, 32(1): 210-213.
doi: 10.3724/SP.J.1146.2009.00042
Abstract:
This paper studies the signal crosstalk due to redundant object defect of adjacent copper interconnects. The models of coupling capacitance and mutual inductance between redundant defect and interconnects are presented, and it can be used to quantitatively calculate the influence of defect on crosstalk. In the experiment model, defect is regard as a separate section RLC circuit. Signal crosstalk is studied under the conditions that are various parameters of interconnect using the model. The far crosstalk and near crosstalk of the copper interconnects are studied. Finally, some advice improved signal crosstalk is put forward. Experiment results show that the presented model can be used actual circuit design, and can guide designer to design circuit for satisfying crosstalk requirements.
This paper studies the signal crosstalk due to redundant object defect of adjacent copper interconnects. The models of coupling capacitance and mutual inductance between redundant defect and interconnects are presented, and it can be used to quantitatively calculate the influence of defect on crosstalk. In the experiment model, defect is regard as a separate section RLC circuit. Signal crosstalk is studied under the conditions that are various parameters of interconnect using the model. The far crosstalk and near crosstalk of the copper interconnects are studied. Finally, some advice improved signal crosstalk is put forward. Experiment results show that the presented model can be used actual circuit design, and can guide designer to design circuit for satisfying crosstalk requirements.
2010, 32(1): 214-218.
doi: 10.3724/SP.J.1146.2008.01718
Abstract:
Through the study of the working principle and structure of Clocked Transmission Gate Adiabatic Logic (CTGAL) and digital comparator, a new design scheme of digital comparator which has the pre-computational function is proposed based on CTGAL. The scheme has the redundancy- restraining function, and it can attain energy saving of about 60% compared to the digital comparator based on PAL-2N. The PSPICE simulation results indicate that this digital comparator has correct logic function and the character of clearly low power.
Through the study of the working principle and structure of Clocked Transmission Gate Adiabatic Logic (CTGAL) and digital comparator, a new design scheme of digital comparator which has the pre-computational function is proposed based on CTGAL. The scheme has the redundancy- restraining function, and it can attain energy saving of about 60% compared to the digital comparator based on PAL-2N. The PSPICE simulation results indicate that this digital comparator has correct logic function and the character of clearly low power.
2010, 32(1): 227-230.
doi: 10.3724/SP.J.1146.2008.01588
Abstract:
A new design method is presented for designing FTFN(Four-Terminal Floating Nullor)-RC filter of arbitrary order with signal flow graph. A FTFN-RC configuration that can be used to realize arbitrary order transfer function is obtained by direct analysis of network function. The filter circuit which contains n active elements, n grounded capacitors and resistors can produce nth order low-pass, band-pass and high-pass filters without changing the internal structure of circuit. So the circuit is simplified and integrated conveniently. PSPICE simulation at the MOS transistor level is carried out and results show that the proposed circuit is feasible.
A new design method is presented for designing FTFN(Four-Terminal Floating Nullor)-RC filter of arbitrary order with signal flow graph. A FTFN-RC configuration that can be used to realize arbitrary order transfer function is obtained by direct analysis of network function. The filter circuit which contains n active elements, n grounded capacitors and resistors can produce nth order low-pass, band-pass and high-pass filters without changing the internal structure of circuit. So the circuit is simplified and integrated conveniently. PSPICE simulation at the MOS transistor level is carried out and results show that the proposed circuit is feasible.
2010, 32(1): 231-234.
doi: 10.3724/SP.J.1146.2009.00345
Abstract:
This paper studies the effect of the varying load on the transmission characteristics of a two-port network and defines the load insensitivity network as the minimum mismatch network. A fifth order minimum mismatch filter is designed by using of Monte Carlo method. The example shows the transmission characteristic of the designed minimum mismatch filter is better than those of the prototype filters, when load impedance is varying. The results demonstrate the minimum mismatch network exists and it can be realized, when a reasonable choice of technical specifications is given.
This paper studies the effect of the varying load on the transmission characteristics of a two-port network and defines the load insensitivity network as the minimum mismatch network. A fifth order minimum mismatch filter is designed by using of Monte Carlo method. The example shows the transmission characteristic of the designed minimum mismatch filter is better than those of the prototype filters, when load impedance is varying. The results demonstrate the minimum mismatch network exists and it can be realized, when a reasonable choice of technical specifications is given.
2010, 32(1): 235-239.
doi: 10.3724/SP.J.1146.2009.00117
Abstract:
The significant problem for the implementation of distributed space-time encoding and decoding in multi-user cooperative MIMO is the adaptive space-time equalization algorithm with low detection complexity and fast convergence property. Space-time Decision Feedback Equalization (DFE) at multi-antenna receiver in Distributed Vertical Bell Labs Layered Space-Time (D-VBLAST) system is studied. RLS-MIMO-DFE detection algorithm based on Least Square (LS) criterion is proposed. Compared with other D-VBLAST detection algorithms such as Maximum Likelihood (ML)、Zero Forcing Ordered Successive Interference Cancellation (ZF-OSIC), the proposed algorithm has the unique property such as the fast convergence and the lower detection complexity. Theoretical derivation and simulated results show that, in D-VBLAST 22 system, although the performance of RLS-MIMO-DFE is a bit inferior to ML detection, the proposed algorithm could compromise the detection performance and computation complexity efficiently, and adapt to channel variation simultaneously. Thus it could satisfy real-time requirements for cooperative nodes in downlink channel.
The significant problem for the implementation of distributed space-time encoding and decoding in multi-user cooperative MIMO is the adaptive space-time equalization algorithm with low detection complexity and fast convergence property. Space-time Decision Feedback Equalization (DFE) at multi-antenna receiver in Distributed Vertical Bell Labs Layered Space-Time (D-VBLAST) system is studied. RLS-MIMO-DFE detection algorithm based on Least Square (LS) criterion is proposed. Compared with other D-VBLAST detection algorithms such as Maximum Likelihood (ML)、Zero Forcing Ordered Successive Interference Cancellation (ZF-OSIC), the proposed algorithm has the unique property such as the fast convergence and the lower detection complexity. Theoretical derivation and simulated results show that, in D-VBLAST 22 system, although the performance of RLS-MIMO-DFE is a bit inferior to ML detection, the proposed algorithm could compromise the detection performance and computation complexity efficiently, and adapt to channel variation simultaneously. Thus it could satisfy real-time requirements for cooperative nodes in downlink channel.
2010, 32(1): 183-188.
doi: 10.3724/SP.J.1146.2009.00461
Abstract:
In order to resolve the problems of concentrating key management and over-consumption on certificate maintenance in space network, an identity-based distributed key management scheme is proposed. On the basis of the properties of space network, the method for constructing distributed private key generators is put forward. According to identity-based cryptography proposed by Boneh and Franklin, the scheme designs the methods of updating private key, updating host-key shares and negotiating session key. Analysis and simulation show that the scheme can meet the safety requirements and has good scalability.
In order to resolve the problems of concentrating key management and over-consumption on certificate maintenance in space network, an identity-based distributed key management scheme is proposed. On the basis of the properties of space network, the method for constructing distributed private key generators is put forward. According to identity-based cryptography proposed by Boneh and Franklin, the scheme designs the methods of updating private key, updating host-key shares and negotiating session key. Analysis and simulation show that the scheme can meet the safety requirements and has good scalability.
2010, 32(1): 219-226.
doi: 10.3724/SP.J.1146.2009.00091
Abstract:
Image Quality Assessment (IQA) is a hot research area in the field of image processing. In this paper, objective and subjective IQA methods are reviewed, and more attention is paid to the former. PSNR and MSE, which are commonly used to assess the quality, are analyzed in detail and their defects are given. The models based on error sensitivity and structure distortion of images are two critical methods in IQA, and the survey presents their key techniques and challenge problems. The reduced reference and no reference methods are also presented in this survey. Based on the number of view, IQA are classified into two major categories, namely, monoscopic image IQA and stereoscopic image IQA. This survey also makes an introduction of the stereoscopic image IQA. Finally, the survey lists several perspective sub-fields and topics in IQA progress.
Image Quality Assessment (IQA) is a hot research area in the field of image processing. In this paper, objective and subjective IQA methods are reviewed, and more attention is paid to the former. PSNR and MSE, which are commonly used to assess the quality, are analyzed in detail and their defects are given. The models based on error sensitivity and structure distortion of images are two critical methods in IQA, and the survey presents their key techniques and challenge problems. The reduced reference and no reference methods are also presented in this survey. Based on the number of view, IQA are classified into two major categories, namely, monoscopic image IQA and stereoscopic image IQA. This survey also makes an introduction of the stereoscopic image IQA. Finally, the survey lists several perspective sub-fields and topics in IQA progress.
