Research On Air Target Detection Based On GNSS-R Signal

In the detection process, the active radar emits detection signal, the hidden is poor and it is easy to be interfered and attacked. Thus, the passive detection technology will emerge as the times require. It uses the radiation source of the target itself or other non-cooperative radiation source as the target radiation source. By receiving the direct wave from the source and the target scattering echo, the Doppler frequency shift of the target echo, the arrival time difference and the angle of arrival are measured. With the development of the global navigation satellite system, and the deep research of the satellite reflected signal technology, a new passive detection method is provided for the air target detection. Satellite navigation is used as a real-time source. The direct signal and the reflected signal of the target are received by the ground receiving stations. After processing the received signals, the target detection, location and velocity are achieved.In this thesis, the research is focused on GNSS-R signal for air target detection and location, the main contributions are as follows:(1) This thesis detailed illustrates the four satellite systems of GNSS and signal structure of GPS, the electromagnetic wave polarization, GNSS direct signal strength, GNSS reflected signal strength, GNSS signal processing of coherent accumulation and non coherent accumulation. Thus, the principle of GNSS-R is deeply and comprehensively expounded.(2) The formulas of multi-source single base positioning model and single source multi-base positioning model for air target three-dimensional coordinates are gave. Time delay, satellite coordinates and receiver coordinates which affects the location accuracy are simulated. The simulation results show that the influence of different factors on the location accuracy is different, multi-source single base model and single source multi-base model have higher location accuracy.(3) The formulas of the Doppler frequency shift for the direct signal and the reflected signal are derived. The direct signal Doppler frequency shift and the reflected signal Doppler frequency shift of GPS satellites and the Beidou satellites are simulated. At the same time, a method is proposed to calculate the velocity of air target by Doppler frequency shift.(4) The software of air target detection based on GNSS-R signal is designed, which is composed of general interface, software description interface, GNSS information interface, target characteristic interface, ground receiving interface and detection analysis interface. The firm theoretical foundation is laid for the use of GNSS-R signal to detect, locate and calculate velocity of the air target.