Detection Of Weak Echo Signals For Multiple Different System Satellites

The target detection system based on the external radiation source does not initiate the signal itself,but instead by the third party non-cooperative radiation source irradiating the target,and then detects the target reflection echo to detect or track the target.The mechanism of the target detection system based on the external radiation source determines that it has the characteristics of "radio silence",so it has the characteristics of anti-reconnaissance,anti-interference and survivability,which is different from the "active detection" mechanism for detecting the target signal.available civilian opportunities for exposure sources include FM radio,terrestrial digital TV signals,communication signals,satellite signals,and so on.Aiming at the low reliability of the target echo detection under single radiation source and the difficulty of weak echo signal detection,In this paper,GPS,DVB-S,INMARSAT are used as external radiation source,a joint detection of weak echo signals under different system satellite radiation sources is proposed.On account of direct wave signal for multiple different frequencies are mixed into the reference channel at the same time,resulting in the problem that suppressing effect of direct wave and multipath signal of the supervise channel is poor.The method first separates the direct wave signals of different frequencies in the reference channel,The direct wave signal is cascaded with the direct wave and multipath interference in the supervise channel by using the adaptive filtering method based on NLMS,which lays the foundation for the subsequent weak echo detection.And the direct wave signals which are separated is relevant to the echo signals respectively,then many differnet delay-Doppler spectrums are obtained.Its maximum value is taken as the detection quantity of each distributed multi-sensor,and the statistical analysis is carried out.And the adaptive detection threshold is designed.Finally,the test results are merged to achieve the purpose of adaptive detection for weak echo.The simulation results show that the method can effectively detect the weak echo signal.Aiming at the problem that the traditional time-frequency two-dimensional coherent detection method is sensitive to the noise of the reference channel,the existing method achieves the purpose of weak echo detection by generalized likelihood ratio or Rao detection method.However,both of these methods are modeled and analyzed under a single radiation.In order to effectively detect the weak echoes in multiple satellites by generalized likelihood ratio method and Rao detection method,this paper firstly models the received signal of the supervise channel in the multi-satellite joint scenario.Then,the maximum likelihood estimation method is used to estimate the unknown parameters of the signal.The detectors based on the two detection algorithms are deduced by the maximum likelihood estimation of these unknown parameters,and the detection statistic is analyzed and the corresponding detection threshold is designed.The simulation results show that under the same conditions,the two detection algorithms have similar detection performance,and can effectively detect the weak echo signal that muiltpath and direct wave are not suppressed in the multi-satellite scene.