| With the rapid development of modern military technology,single target detection method is difficult to meet the ever-changing battlefield needs.Using self-developed BeiDou Navigation Satellite System as a radiation source for non-cooperative exploration of large sea targets enhances the military value of the Beidou navigation system,which is also important to supplement the defense technology of coastal defense in China.By using Beidou GEO satellite as a third party radiation source,this thesis analyzes the research results of the existing related fields,studies key technologies of detecting the reflected waves from the sea surface,and discusses key technical problems.The main jobs and innovations of this thesis are as follows:(1)The basic principle of non-cooperative detection using Beidou satellite radiation source is studied.Based on the analysis of the characteristics of the Beidou radiation source,this thesis studies the performance and difference of three types of satellites in the Beidou system space.We choose the "Beidou II" GEO satellite,which is the most suitable for this topic,as a non-cooperative radiation source and establish a spatial geometric model.The Beidou B1 I signal of the open frequency band is studied,and its related characteristics are simulated.The LEO satellite is chosen as the receiver platform of this topic,and its characteristics are simulated and analyzed.The basic principle of non-cooperative exploration of sea targets is studied.What's more,the overall technical road map is put forward.(2)The performance of using the Beidou satellite radiation source to detect sea surface targets is analyzed.Aimed at the polarization characteristics of the Beidou B1 I signal and the polarization characteristics of the reflected wave,a dual antenna dual channel signal receiving method is proposed.The performance of the non-cooperative detection system is analyzed.The detection distance and the required signal processing gain are also calculated.Results of the simulation show that the Beidou B1 I signal is suitable as a non-cooperative detection of the radiation source signal.(3)A weak signal processing algorithm using the Envelope Replaced Differentially Coherent Integration algorithm is proposed.Firstly,the principle of Beidou weak signal acquisition is studied,and the correlation between Beidou distance code is analyzed,and the simulation experiment is done.Secondly,three frequently used Beidou signal acquisition methods are discussed,and the characteristics of each method are summarized.Then,three existing weak signal accumulation techniques are studied.Both their advantages and disadvantages are summarized.Finally,considering the practicality,an Envelope Replaced Differentially Coherent Integration algorithm is proposed based on the existing algorithms,its probabilities and false alarm probabilities are analyzed.The simulation results show that the new algorithm is superior to the original algorithm under low signal-to-noise ratio,and the new algorithm is less dependent on the hardware.It is more suitable for the onboard receiver than the traditional signal accumulation algorithm.(4)The direct channel assisted technique of Beidou satellite receiver is proposed.The two channel design of the receiver enables the acquisition of prior information from the direct channel in order to help acquiring the weak signal in the reflected channel when the reflected signal is captured.In this thesis,firstly,the basic flow of direct channel aided algorithm is proposed,its related parameters are analyzed and deduced.Secondly,this thesis analyzes the influence of the direct channel on the reflected signal is analyzed,and the reason for the increase of the acquisition sensitivity and the acquisition time.Finally,the effectiveness of the direct channel assistant algorithm is proved by simulation experiments,and the performance of the direct channel assistant algorithm is simulated under different SNR conditions. |
PDF Full Text Request