Research On Key Technologies For Passive Radar At UAV Platform Based On GPS

With the development of electronic technologies,some inherent defects of traditional radars have been exposed clearly,such as easily being detected or jammed,and being helpless in detecting low altitude and small targets.Since civilian signals are adopted as radiation sources,passive radar systems are often considered to be good at survival and anti-interference.In addition,civilian signals are widely distributed at different altitude and frequency bands,it brings the potentialities in anti-stealth and low altitude detection.Therefore,the research of passive radar is getting more and more attention.However,passive radar also has some problems,such as weak echo from target and considerable influence from environmental clutter.Using GPS(Global Positioning System)as a third-part transmitter and using unmanned aerial vehicle(UAV)as receiving platform,we mainly study some key technical issues in passive radar includes:1.Having researched the signal processing flow of GPS signal as radiation source.In this part,the structural characteristics of GPS signal especially the C/A code were analyzed.And the feasibility of the GPS as a radiation source were discussed from the aspects of the ambiguity function and maximum detection range,etc.2.Aiming at the key processing flow of passive radar system,a direct wave purification method for multi-satellite data fusion using signal reconstruction was proposed.Combined with the actual situation in this paper,the clutter simulation is carried out on the airborne bistatic radar and has analyzed clutter characteristics.Adopting an algorithm combining orthogonal projection(OP)with angel-doppler compensation(ADC)as OP-ADC algorithm to compensate range dependence.The reduced-dimension space-time adaptive processing algorithms(STAP)has been used for clutter suppression.In addition to the weak signal of GPS,coordinate transformation is used to achieve signal fusion between multiple satellites to increase signal strength.3.Facing the weak characteristics of the echo signal,a long-term coherent accumulation was adopted to increase the signal-to-noise ratio.In view of the large amount of long-term coherent accumulated data,a block processing method was used to achieve coherent accumulated processing.Besides,it focuses on the research of range migration problem caused by long-term coherent accumulation and analyzes the causes of range migration.Aiming at the problem of range migration,three methods,sinc interpolation,DFT transform and Chirp-z transform were investigated to analyze the performance of range migration correction.4.The target localization method using time difference of arrival(TDOA)and the optimal station distribution of the target on the air receiving platform have been studied.geometric dilution of precision(GDOP)is adopted as the main measure.Also,the other factors that affecting location accuracy such as geometrical station placement and baseline length have been discussed.