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In order to achieve fast and accurate passive location of the target radiation source, this paper puts forward a Virtual Time Reversal Method Based on Uniform Linear Array (ULA-VTR) passive location algorithm. This framework employs the passive time reversal focusing theory, which does not to require the physical transmission of time reversal signals and does not require pre-estimation of the channel to realize passive direction finding. The above principle is utilized to perform the target radiation source signal through a uniform linear sensor array for detection. The article provides the signal model of linear time reversal array and the virtual retransmission process in the first place. Then utilizes ULA-VTR to establish a dual-station passive location framework and derives the coordinate transformation equation to find its observation angle, in addition, establishes the observation equation system for obtaining the site of the target radiation source. Ultimately, the paper analyses the computational complexity of the ULA-VTR algorithm and adopts Geometric Dilution of Precision(GDOP) to discuss the positioning performance. The experimental results indicate that the technique presented in this paper has higher positioning accuracy under the low SNR compared with other techniques.

This paper presents a passive direction finding of a virtual time reversal method based on cross antenna array (CROSS-VTR), which aim is to solve the problem that the number of antenna elements of planar arrays is too large and the layout of circular arrays is complex which requires high hardware design. In order to verify the feasibility and accuracy of the algorithm, the mathematical model of the cross antenna array is first established. The search area of yaw angle and a pitch angle of the CROSS-VTR algorithm is determined according to the basic principle of passive time reversal focusing, and then, the time-reversed signal of each antenna element completes the time delay compensation at each scanning point in the search area. The compensated signals of each antenna element are added up to obtain the signal energy of each scanning point. The value of the yaw angle and pitch angle is obtained by searching the maximum energy among scanning points along the search route of yaw angle and pitch angle, respectively. Finally, the validity of the method is verified and compared with the music algorithm (multiple signal classification) based on the cross antenna array. The results show that the method has good direction finding accuracy at low signal-to-noise ratio.

The paper describes the principles and techniques used to detect signals propagating in the atmosphere in the infrasonic frequency range. Such signals can be generated by different sources: ground and atmospheric explosions, as well as objects moving in the atmosphere at supersonic speed (aircraft, rockets, bolides, fragments of spent stages of launch vehicles). Portable infrasound monitoring stations are described, each of which includes three spaced infrasonic microphones. Each such station makes it possible to determine three basic parameters of the detected infrasound signal, which are subsequently used to solve the direction- finding problem: the time of arrival of an infrasonic wave, the azimuth to the source in the horizontal plane, and the wave approach angle from the source of infrasonic waves to the Earth’s surface in the vertical plane. An acoustic detector used to extract useful signals against a noise background is described. The detector is based on an algorithm similar to the STA/LTA detection algorithm known in seismology. Examples of the operation of an acoustic detector with data obtained during real measurements are given. Passive infrasound direction-finding technology is described. It is based on mathematical modeling of the of infrasonic wave propagation in the atmosphere, which are generated by objects moving along possible trajectories; comparison of theoretical signals with real ones recorded by monitoring stations; and determination of the realized trajectories. The paper gives examples of experimental verification of the effectiveness of passive infrasound direction-finding technology for determining the impact points of the first and second stages of launch vehicles. It is shown that infrasound direction-finding systems makes it possible to reduce the estimated search area for launch vehicle fragments that fall to the Earth, significantly decrease the time and costs for their search and utilization, and mitigate the negative environmental impact of the rocket and space industry. [ABSTRACT FROM AUTHOR]