Low Altitude Environment Sensing Technology Based On SFR And Monitoring Software Development

With the further opening of China’s low-altitude environment, the number of the low-altitude aircrafts increased significantly and the flight environment at low altitude becomes more and more complex,the demand for low-altitude environment sensing technology gets increasingly urgent.For the sensing of stationary targets in the low-altitude environment,proceeding the research of obtaining HRRP using step frequency radar.The traditional way to obtain the HRRP requires cumbersome procedures to deal with the redundancy.To solve this problem,using the bandwidth synthesizing method to obtain the HRRP of the targets.The method requires a complete frame of echo,and the process is as follows:firstly, each single pulse should be upsampled;secondly, it is needed to perform pulse compression operation on each single pulse; thirdly, shifting the spectrum of each pulse; finally, synthesizing the shifted results to gain an equivalent large bandwidth signal. The processing results of simulation data prove that, under the low noise-signal-ratio circumstances,the bandwidth synthesizing method has obvious advantage over the accumulation method and the selection method.For the sensing of moving targets in the low-altitude environment,proposing the velocity searching method based on frame correlation.This method works in two procedures.The first procedure is as follows:firstly,it is needed to take correlation operation between frames;secondly,accumulating the correlation results within each frame;thirdly,selecting efficient samples based on 3 d B principle to construct the covariance matrix; fourthly, based on the eigenvalue decomposition of the covariance matrix,obtaining the velocity spectrum by using single snapshot method; finally,searching the velocity spectrum to obtain the first velocity estimation result.The second procedure is as follows: firstly, compensating the envelope and phase of the echo using the first velocity estimation result;secondly,performing pulse compression operation on the compensating results; thirdly,synthesizing the compression results within each frame; fourthly, performing an FFT on the synthesizing results to obtain an doppler-range image; finally, based on the doppler offset,obtaining the etimation of velocity residual,and then obtaining the second velocity estimation result.Duplicating the second procedure using the second velocity estimation result to obtain the final imaging result.Searching the final imaging result to obtain the initial location information.In order to avoid the influence of strong target,performing a projection processing on the correlation results of the echo using the speed orthogonal matrix which is constructed by the second velocity estimation to suppress the strong signal.This method has the advantage of higher velocity estimation accuracy over the time domain correlation method.In order to display the detection results of muti-sensors,developing the monitoring software. This software uses client-server model,in which the multi sensors are the clients and the ground base station is the server.To guarantee the security and order of the data,using the way for links to transmit.The programming platform is VC6.0,and the network communication programming uses the socket.To ensure that the data transmission do not affect the implementation of other tasks,using multi-thread programming method.This software implements the dynamic and parallel display of the multi-sensors’ detection results.