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2001 Vol. 23, No. 6
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2001, 23(6): 521-527.
Abstract:
In this paper, a semi-blind closed-form co-channel signal separation method is proposed, which is based on two steps. The first is to estimate the zero space of multi-users signals. The second is to estimate them using LMS method and some short sequence, which is always known in digital communication system. Compared with non-blind ones, the new method needs very short sequence, the shortest length of which is equal to the number of co-channel users. At the same time it can overcome the shortcoming of blind ones in computational complexity and lack of global convergence. The computer simulation demonstrates that the. new method is suitable for co-channel signal separation in smart antenna systcin when mult,ipath exists.
In this paper, a semi-blind closed-form co-channel signal separation method is proposed, which is based on two steps. The first is to estimate the zero space of multi-users signals. The second is to estimate them using LMS method and some short sequence, which is always known in digital communication system. Compared with non-blind ones, the new method needs very short sequence, the shortest length of which is equal to the number of co-channel users. At the same time it can overcome the shortcoming of blind ones in computational complexity and lack of global convergence. The computer simulation demonstrates that the. new method is suitable for co-channel signal separation in smart antenna systcin when mult,ipath exists.
2001, 23(6): 528-532.
Abstract:
A novel discrete-time digital channel blind estimation algorithm is proposed, which reduces the complexity of the optimal estimation considerably by using the one-step branch transition rules of trellis. In this paper, the optimal estimation algorithm based on the maximum likelihood sequence estimation is introduced first. Then the idea of selecting trellises based on the one-step branch transition rules in a trellis is explained. Following the presentation of the novel channel blind estimation algorithm, the performance of this algorithm is studied with computer simulation.
A novel discrete-time digital channel blind estimation algorithm is proposed, which reduces the complexity of the optimal estimation considerably by using the one-step branch transition rules of trellis. In this paper, the optimal estimation algorithm based on the maximum likelihood sequence estimation is introduced first. Then the idea of selecting trellises based on the one-step branch transition rules in a trellis is explained. Following the presentation of the novel channel blind estimation algorithm, the performance of this algorithm is studied with computer simulation.
2001, 23(6): 533-539.
Abstract:
In this paper the relations between hash functions and authentication codes are discussed, and some special hash function classes are in particular researched. Some constructions of -AU and -ASU hash function classes are given, with which the simple and efficient authentication codes are constructed.
In this paper the relations between hash functions and authentication codes are discussed, and some special hash function classes are in particular researched. Some constructions of -AU and -ASU hash function classes are given, with which the simple and efficient authentication codes are constructed.
2001, 23(6): 540-544.
Abstract:
In this paper, a family of perfect reconstruction filter banks suitable for multi-scale edge extraction is constructed . Experimental result is given to show its correctness and effectiveness.
In this paper, a family of perfect reconstruction filter banks suitable for multi-scale edge extraction is constructed . Experimental result is given to show its correctness and effectiveness.
2001, 23(6): 545-551.
Abstract:
The passive location is a key in many applications. It is a difficult question to estimate trajectories of multiple moving sources with single moving station. This paper deals with the estimation of motion parameters of multiple sources in the passive array processing. It uses basically state-space model of the spatial-temporal data. The interpolation signal procedures play a fundamental role and link the spatial and temporal analysis. Using uniformity linear array and MDL and ESPRIT algorithms, the numbers, center frequencies of sources, spatial frequency and spatial frequency change speed can be estimated together. Further the trajectories (i.e., position and velocity) of every source can be estimated.
The passive location is a key in many applications. It is a difficult question to estimate trajectories of multiple moving sources with single moving station. This paper deals with the estimation of motion parameters of multiple sources in the passive array processing. It uses basically state-space model of the spatial-temporal data. The interpolation signal procedures play a fundamental role and link the spatial and temporal analysis. Using uniformity linear array and MDL and ESPRIT algorithms, the numbers, center frequencies of sources, spatial frequency and spatial frequency change speed can be estimated together. Further the trajectories (i.e., position and velocity) of every source can be estimated.
2001, 23(6): 552-558.
Abstract:
The paper describes the concepts of reconstruction of phase space, correlation dimension, Lyapunov exponent and power spectrum exponent. The calculations presented is based on experimental radar data which confirm the chaotic nature of sea clutter. In particular, the results of the calculations show that the first Lyapunov exponent of sea clutter is indeed positive. Such a result is an inherent characteristic of a chaotic process.
The paper describes the concepts of reconstruction of phase space, correlation dimension, Lyapunov exponent and power spectrum exponent. The calculations presented is based on experimental radar data which confirm the chaotic nature of sea clutter. In particular, the results of the calculations show that the first Lyapunov exponent of sea clutter is indeed positive. Such a result is an inherent characteristic of a chaotic process.
2001, 23(6): 559-568.
Abstract:
This paper analyzes the special characteristics of impulse signal S AR ,in the process of imaging. In condition of sending, receiving UWB signal with big accumulating angle, the formulation of azimuth resolution is deduced. Single cycle and double cycle signals used in impulse SAR imaging are analyzed and contrasted. Some conclusions are given. Finally, they are proved to be right by the simulation results.
This paper analyzes the special characteristics of impulse signal S AR ,in the process of imaging. In condition of sending, receiving UWB signal with big accumulating angle, the formulation of azimuth resolution is deduced. Single cycle and double cycle signals used in impulse SAR imaging are analyzed and contrasted. Some conclusions are given. Finally, they are proved to be right by the simulation results.
2001, 23(6): 569-576.
Abstract:
Radio Frequency Interference (RFI) plays an important role on the quality of Ultra-Wide Band Synthetic Aperture Radar (UWB-SAR) imaging. Being modeled as sinusoidal signals, the RFI can be greatly suppressed by the method of iterative Maximum Likelihood (ML) estimation. However, the problems of local minimum and separation of close frequencies exist. In this paper, the difficulty is considerably reduced by the use of eigenstructure analysis to give a better initial frequency estimation. The algorithm is further simplified using a binary hypothesis test, on the number of sinusoidal signals in one spectral peak. The excellent performance of the algorithm is demonstrated by experiments on simulated and real RFI data.
Radio Frequency Interference (RFI) plays an important role on the quality of Ultra-Wide Band Synthetic Aperture Radar (UWB-SAR) imaging. Being modeled as sinusoidal signals, the RFI can be greatly suppressed by the method of iterative Maximum Likelihood (ML) estimation. However, the problems of local minimum and separation of close frequencies exist. In this paper, the difficulty is considerably reduced by the use of eigenstructure analysis to give a better initial frequency estimation. The algorithm is further simplified using a binary hypothesis test, on the number of sinusoidal signals in one spectral peak. The excellent performance of the algorithm is demonstrated by experiments on simulated and real RFI data.
2001, 23(6): 577-582.
Abstract:
This paper explores a new method of the simultaneous scattering matrix measurement-dividing in frequency domain. In this method, two chirp signals with same slope but different central frequency are transmitted simultaneously through two antennas. One is a horizontal polarization antenna and another is a vertical polarization antenna. The dispersion of the two central frequencies is not smaller than the bandwidth of the chirp signals. The return signals are received through two antennas simultaneously. Each...
This paper explores a new method of the simultaneous scattering matrix measurement-dividing in frequency domain. In this method, two chirp signals with same slope but different central frequency are transmitted simultaneously through two antennas. One is a horizontal polarization antenna and another is a vertical polarization antenna. The dispersion of the two central frequencies is not smaller than the bandwidth of the chirp signals. The return signals are received through two antennas simultaneously. Each...
2001, 23(6): 583-588.
Abstract:
Based on unidirectionally coupling method, the synchronization through compound chaotic signal is studied. This method of synchronization is applied to Murali-Lakshmanan-Chua circuit, and a sufficient condition for synchronization in MLC circuit via Bellman-Gronwall inequality is given.
Based on unidirectionally coupling method, the synchronization through compound chaotic signal is studied. This method of synchronization is applied to Murali-Lakshmanan-Chua circuit, and a sufficient condition for synchronization in MLC circuit via Bellman-Gronwall inequality is given.
2001, 23(6): 589-596.
Abstract:
This paper deals with k-fault location of active networks with four controlled sources. It is verified by means of nullors, that the algorithm for active networks is identical to that for passive networks. Furthermore, the local testability and global testability are topologically discussed for active networks.
This paper deals with k-fault location of active networks with four controlled sources. It is verified by means of nullors, that the algorithm for active networks is identical to that for passive networks. Furthermore, the local testability and global testability are topologically discussed for active networks.
2001, 23(6): 597-602.
Abstract:
Considering the complexity of solution for the problem of electromagnetic shielding by using precise boundary conditions, in order to simplify analysis and calculation of the boundary-value problem of electromagnetic shielding, on the basis of averaged boundary conditions, a new method of solution for the boundary-value problem of the electromagnetic shielding on a moving thin conducting plate is presented. Compared with the solution obtained by using precise boundary conditions, the method presented in this paper is very simple and convenient, and in the applied limits of averaged boundary conditions, the distribution of electromagnetic fields in the free space outside the plate can be calculated with satisfactory accuracy.
Considering the complexity of solution for the problem of electromagnetic shielding by using precise boundary conditions, in order to simplify analysis and calculation of the boundary-value problem of electromagnetic shielding, on the basis of averaged boundary conditions, a new method of solution for the boundary-value problem of the electromagnetic shielding on a moving thin conducting plate is presented. Compared with the solution obtained by using precise boundary conditions, the method presented in this paper is very simple and convenient, and in the applied limits of averaged boundary conditions, the distribution of electromagnetic fields in the free space outside the plate can be calculated with satisfactory accuracy.
2001, 23(6): 603-610.
Abstract:
In this paper the scattering characteristics of dielectric periodic structures by an oblique incidence are analyzed by a method which combines the multimode network approach with rigorous mode matching method. The dependence of frequency selective characteristics of the 3-D frequency selective surface(FSS) structures on frequency and angle of the incident wave and the structure parameters is quantitatively studied. Therefore, some guidelines for design and application of the 3-D FSS structures are given.
In this paper the scattering characteristics of dielectric periodic structures by an oblique incidence are analyzed by a method which combines the multimode network approach with rigorous mode matching method. The dependence of frequency selective characteristics of the 3-D frequency selective surface(FSS) structures on frequency and angle of the incident wave and the structure parameters is quantitatively studied. Therefore, some guidelines for design and application of the 3-D FSS structures are given.
2001, 23(6): 617-621.
Abstract:
In this paper, a multi-mode signal generation system based on high speed ECL digital circuits is introduced. The method to design LFM and NLFM signal systems is also discussed. The implemented system working at clock frequency of 280MHz can output LFM and NLFM signals with different time duration and frequency bands within 70MHz. The measurement results of the system show that its performances of harmonic and spurious signals less than-55dB. It can meet the needs of practical engineering applications.
In this paper, a multi-mode signal generation system based on high speed ECL digital circuits is introduced. The method to design LFM and NLFM signal systems is also discussed. The implemented system working at clock frequency of 280MHz can output LFM and NLFM signals with different time duration and frequency bands within 70MHz. The measurement results of the system show that its performances of harmonic and spurious signals less than-55dB. It can meet the needs of practical engineering applications.
2001, 23(6): 622-624.
Abstract:
Using microwave plasma-assisted chemical vapor deposition system, the nitrogen dopeed amorphaus-carbon films are obtained on the deposited molybdenum films, which are deposited on ceramic (Al2O3). The scanning electron microscopy (SEM), optical microscopy, X-ray diffraction (XRD) and Raman spectrum are used to analyze the obtained. Experimental results show that, when increasing the nitrogen, the eaission current density increases and the turn-on field decreases.
Using microwave plasma-assisted chemical vapor deposition system, the nitrogen dopeed amorphaus-carbon films are obtained on the deposited molybdenum films, which are deposited on ceramic (Al2O3). The scanning electron microscopy (SEM), optical microscopy, X-ray diffraction (XRD) and Raman spectrum are used to analyze the obtained. Experimental results show that, when increasing the nitrogen, the eaission current density increases and the turn-on field decreases.
2001, 23(6): 611-616.
Abstract:
DCS mesh network is the main topology of telecommunication backbone network. In this paper, self-healing of SDH/ATM/WDM DCS mesh network and their relationships are discussed. Relationship of transport network self-healing and service network is also discussed.
DCS mesh network is the main topology of telecommunication backbone network. In this paper, self-healing of SDH/ATM/WDM DCS mesh network and their relationships are discussed. Relationship of transport network self-healing and service network is also discussed.
