Research On TDOA/FDOA Location Technology Of Search And Rescue Signal

In wireless communication network and satellite communication,passive positioning technology has played a very important role in the positioning of target radiation sources and interference sources.Compared with radar positioning technology,passive positioning technology adopts a passive positioning mode that does not need to emit electromagnetic waves by itself,thereby realizing silent radio positioning.Therefore,it has a wide range of application prospects in the fields of air disasters and maritime distress,and has great research value.This paper mainly studies the passive positioning technology based on Time Difference of Arrival(TDOA)and Frequency Difference of Arrival(FDOA)as position positioning elements.,three aspects of positioning methods have been studied,the specific contents are as follows:First,the Global Satellite Search and Rescue System is introduced,which is an important part of the Global Maritime Distress and Safety System implemented by Inmarsat.The low-earth orbit satellite search and rescue system,the medium-orbit satellite search and rescue system and the geostationary orbit satellite search and rescue system are introduced from the aspects of interoperability and performance indicators.Advantages of Orbital Satellite Search and Rescue Systems.Secondly,according to the principle of passive positioning,a dual-satellite TDOA/FDOA positioning model is established,and the positioning equation is derived.The Newton algorithm and the analytical algorithm in the binary star positioning solution method are studied.The simulation results show the availability of the two positioning solution methods.Then,the commonly used time-frequency difference joint estimation algorithm is introduced,and the TDOA/FDOA joint estimation formula based on mutual ambiguity function is deduced according to the principle of double-star positioning.The 406 MHz distress signal uses BPSK modulation as the transmit signal.The time difference and frequency difference calculated by mutual ambiguity are greatly affected by the channel noise.On this basis,a method based on time domain windowing to remove channel invalid information is proposed.,splicing together the received distress signals in the time domain.According to the theoretical simulation results,the more effective information for help is received,the more accurate the calculated time difference and frequency difference are,and the theoretical value is continuously approached.Finally,in the emergency distress scenario,the sender of the distress signal can only see one satellite under the condition of limited field of view.Here,a single-satellite time-frequency difference time measurement and positioning technology is proposed,which introduces the geometric dilution precision factor GDOP(Geometrical Dilution of Precision)and deduce the GDOP formula to analyze the relationship between the positioning effect and various error factors.The influence of time interval and frequency interval change rate on the positioning accuracy is analyzed through the actual measurement of search and rescue positioning.