A fast separable approach based on a cross array is presented, which has coarsegrained parallelism. Its computational load is far less than that of the two-dimensional (2-D) direct processing method and other existing...A fast separable approach based on a cross array is presented, which has coarsegrained parallelism. Its computational load is far less than that of the two-dimensional (2-D) direct processing method and other existing separable approaches. In order to compensate for the performance degradation due to separable processing, two postprocessing schemes are also proposed. Some computer simulation results are provided for illustration in the end.展开更多
Traditional approaches of spatial spectral estimation are usually based on the second-order statistics. The higher-order cumulants and the poly-spectrum contain more information and are capable of reducing the Gaussia...Traditional approaches of spatial spectral estimation are usually based on the second-order statistics. The higher-order cumulants and the poly-spectrum contain more information and are capable of reducing the Gaussian noise. In this paper, we present a new spectrum estimation method for direction-finding, the FOMUSIC algorithm, which is based on the eigen-structure analysis of the fourth-order cumulants. The derivation of the algorithm is given in detail and its performance is illustrated by both the computer simulations and the experiments of a direction-finding system. The obtained results demonstrate that the fourth-order cumulants based method outperforms the traditional methods, especially when the noise is an unknown colored one.展开更多
For the applications of Alpha very-low-frequency(VLF) systems consisting of multiple transmitters, determining the origin transmitter station of received signals is a crucial problem. Based on single-station observati...For the applications of Alpha very-low-frequency(VLF) systems consisting of multiple transmitters, determining the origin transmitter station of received signals is a crucial problem. Based on single-station observations, this study develops a directionfinding method to extract Russian Alpha transmitter signals. First, the amplitudes of Alpha signals received in Suizhou City,Hubei Province(31.57°N, 113.32°E) in the east-west(EW) and north-south(NS) directions are obtained by the power spectrum method. The amplitude ratios of signals in the two directions are subsequently adopted to estimate the propagation angles of the signals with respect to the NS direction of the VLF receiver station. Phase ambiguity in our system is eliminated by comparing Alpha signal waveform with that from the VTX transmitter in India(8.39°N, 77.75°E) as a reference station. Finally, we can determine the quadrant where the incoming wave signals are located relative to the receiver and eventually distinguish the exact Alpha transmitters. Based on the direction-finding results, the amplitudes of each Alpha signal are extracted, and their diurnal variation features are analyzed to verify the performance of our method. These results are of great significance for the further study of Alpha signals and VLF long-distance communication.展开更多
文摘A fast separable approach based on a cross array is presented, which has coarsegrained parallelism. Its computational load is far less than that of the two-dimensional (2-D) direct processing method and other existing separable approaches. In order to compensate for the performance degradation due to separable processing, two postprocessing schemes are also proposed. Some computer simulation results are provided for illustration in the end.
文摘Traditional approaches of spatial spectral estimation are usually based on the second-order statistics. The higher-order cumulants and the poly-spectrum contain more information and are capable of reducing the Gaussian noise. In this paper, we present a new spectrum estimation method for direction-finding, the FOMUSIC algorithm, which is based on the eigen-structure analysis of the fourth-order cumulants. The derivation of the algorithm is given in detail and its performance is illustrated by both the computer simulations and the experiments of a direction-finding system. The obtained results demonstrate that the fourth-order cumulants based method outperforms the traditional methods, especially when the noise is an unknown colored one.
基金supported by the pre-research projects on Civil Aerospace Technologies (Grant Nos. D020303,D020104,and D020308)the China National Space Administration by the B-type Strategic Priority Program of the Chinese Academy of Sciences (Grant No. XDB41000000)+1 种基金the Fundamental Research Funds for the Central Universities (Grant Nos. 2042021kf1045 and 2042021kf1056)the National Natural Science Foundation of China (Grant Nos. 42188101,42025404,41674163,41974186,41704162,41904144,and 41904143)。
文摘For the applications of Alpha very-low-frequency(VLF) systems consisting of multiple transmitters, determining the origin transmitter station of received signals is a crucial problem. Based on single-station observations, this study develops a directionfinding method to extract Russian Alpha transmitter signals. First, the amplitudes of Alpha signals received in Suizhou City,Hubei Province(31.57°N, 113.32°E) in the east-west(EW) and north-south(NS) directions are obtained by the power spectrum method. The amplitude ratios of signals in the two directions are subsequently adopted to estimate the propagation angles of the signals with respect to the NS direction of the VLF receiver station. Phase ambiguity in our system is eliminated by comparing Alpha signal waveform with that from the VTX transmitter in India(8.39°N, 77.75°E) as a reference station. Finally, we can determine the quadrant where the incoming wave signals are located relative to the receiver and eventually distinguish the exact Alpha transmitters. Based on the direction-finding results, the amplitudes of each Alpha signal are extracted, and their diurnal variation features are analyzed to verify the performance of our method. These results are of great significance for the further study of Alpha signals and VLF long-distance communication.
