A research is done for multipath effects of low-angle tracking in meter-wave radar, and the theory of multi-scattering centers of complex target is discussed as well as the character of reflected echoes. This points o...A research is done for multipath effects of low-angle tracking in meter-wave radar, and the theory of multi-scattering centers of complex target is discussed as well as the character of reflected echoes. This points out that the distribution and scattering properties of scattering centers are the prime reasons which cause the variation of muhipath effects, and all the changes of position, motion and attitude of the target can influence the muhipath effects. By building of muhipath model for multi-scattering centers for target, the analysis above is verified and a new method of elevation estimation for low-angle target is presented. The new method uses canceling vectors obtained by searching to cancel reflected waves in echoes and reduce the influence of reflected com- ponents, which can improve the accuracy of elevation estimation of low-angle target and the performance of low- angle tracking in meter-wave radar. Experimental results verify the availability of the method.展开更多
Radio Frequency(RF) technology represents a high-precision relative navigation solution that has significant potential for application to earth-orbiting satellites. In precision applications, multipath errors dominate...Radio Frequency(RF) technology represents a high-precision relative navigation solution that has significant potential for application to earth-orbiting satellites. In precision applications, multipath errors dominate the total error because observables, which are used to estimate carrier-phase integer ambiguity, are not always subject to a Gaussian distribution when dualfrequency ambiguity estimation methods are used in the presence of multipath. As it has been shown that ranging observables obey a Gaussian mixture distribution, this study proposes improvements to the accuracy of estimation based on multipath mitigation founded on the Gaussian mixture model. To this end, such a model is created for integer ambiguity resolution in the presence of multipath, using which the theoretical error in dual-frequency ambiguity estimation is derived.Expectation Maximization(EM), which aids dual-frequency ambiguity estimation, is subsequently proposed to reduce the effect of multipath errors. Finally, two experimental scenarios are implemented to test the performance of the proposed method. The results show that EM-aided dualfrequency ambiguity estimation reduces the range error to approximately 20% in comparison with simple dual-frequency ambiguity estimation. Therefore the proposed technique is effective for multipath mitigation in RF relative measurement.展开更多
Home power outlets can be connected in various topologies： derivation, star, cascade. This paper firstly describes the intrinsic behavior of the transfer function of these basic topologies. Secondly, the channel capa...Home power outlets can be connected in various topologies： derivation, star, cascade. This paper firstly describes the intrinsic behavior of the transfer function of these basic topologies. Secondly, the channel capacities of the three topologies are compared to check if there is a more favorable topology. Many deterministic modeling methods have been developed to compute the transfer function of power line networks but the given examples in the studies correspond only to the derivation topology with branches connected to the direct path between transceivers. Thirdly, this paper evaluates the ability of common modeling methods （multipath and chain matrices） to compute accurately the transfer function of any topology. Modeling the derivation topology with ＂secondary＂ branches and the star topology is shown to be inappropriate with chain matrices based method. Indeed, this method is very sensitive to the uncertainty of the second parameters of the power cables and this induces considerable fading shifts for those topologies. Multipath modeling method produces results agreeing with measurements for any topology.展开更多
文摘A research is done for multipath effects of low-angle tracking in meter-wave radar, and the theory of multi-scattering centers of complex target is discussed as well as the character of reflected echoes. This points out that the distribution and scattering properties of scattering centers are the prime reasons which cause the variation of muhipath effects, and all the changes of position, motion and attitude of the target can influence the muhipath effects. By building of muhipath model for multi-scattering centers for target, the analysis above is verified and a new method of elevation estimation for low-angle target is presented. The new method uses canceling vectors obtained by searching to cancel reflected waves in echoes and reduce the influence of reflected com- ponents, which can improve the accuracy of elevation estimation of low-angle target and the performance of low- angle tracking in meter-wave radar. Experimental results verify the availability of the method.
基金supported by the National Natural Science Foundation of China(No.91438116)the Program for New Century Excellent Talents of China(No.NCET-12-0030)
文摘Radio Frequency(RF) technology represents a high-precision relative navigation solution that has significant potential for application to earth-orbiting satellites. In precision applications, multipath errors dominate the total error because observables, which are used to estimate carrier-phase integer ambiguity, are not always subject to a Gaussian distribution when dualfrequency ambiguity estimation methods are used in the presence of multipath. As it has been shown that ranging observables obey a Gaussian mixture distribution, this study proposes improvements to the accuracy of estimation based on multipath mitigation founded on the Gaussian mixture model. To this end, such a model is created for integer ambiguity resolution in the presence of multipath, using which the theoretical error in dual-frequency ambiguity estimation is derived.Expectation Maximization(EM), which aids dual-frequency ambiguity estimation, is subsequently proposed to reduce the effect of multipath errors. Finally, two experimental scenarios are implemented to test the performance of the proposed method. The results show that EM-aided dualfrequency ambiguity estimation reduces the range error to approximately 20% in comparison with simple dual-frequency ambiguity estimation. Therefore the proposed technique is effective for multipath mitigation in RF relative measurement.
文摘Home power outlets can be connected in various topologies： derivation, star, cascade. This paper firstly describes the intrinsic behavior of the transfer function of these basic topologies. Secondly, the channel capacities of the three topologies are compared to check if there is a more favorable topology. Many deterministic modeling methods have been developed to compute the transfer function of power line networks but the given examples in the studies correspond only to the derivation topology with branches connected to the direct path between transceivers. Thirdly, this paper evaluates the ability of common modeling methods （multipath and chain matrices） to compute accurately the transfer function of any topology. Modeling the derivation topology with ＂secondary＂ branches and the star topology is shown to be inappropriate with chain matrices based method. Indeed, this method is very sensitive to the uncertainty of the second parameters of the power cables and this induces considerable fading shifts for those topologies. Multipath modeling method produces results agreeing with measurements for any topology.
