Design And Imaging Of SAR System Based On Near-Space

Near-space is emerging as a research hotspot at present, to create the radar platform in Near-space is one of the focal points.Some analysis and discussion in details has been made about architecture and layout of Synthetic Aperture Radar(SAR), whiles some theoretical studies of imaging and motion compesation has been done and simulation has been achieved in this article.The main results and achievements are as below:1. The platform of SAR system based on Near-Space has been given. Pointed out that the radar systems need to have high frequency stability of the local oscillator reference frequency; the antenna subsystem is subject to the platform control system's real-time monitoring; a mechanism that data has been processed before transmission data-processing and transmission system has been established; a good communication mechanism should be established between platform control system and ground system.2. A preliminary analysis about Single-Static Bistatic and Muti-Static SAR in Near-Space has been made. Point out that Single-Static SAR in Near-Space has stronger anti-jamming compared to Airborne SAR, smaller transmit power and higher resolution compared to Satellite SAR; and put forward a proposal to establish a network model. Bistatic SAR in Near-Space has small echo attenuation compared to Single-Static, and a far operating distance, excellent ability of interception resistance, but need high synchronization and has complex motion compensation.In addition, point out the merit and demerit of the model of Bistatic SAR. Distributed Multi-Static can get high quality SAR images, has excellent ability of GMIT, and suitable for IFSAR.3. Detailed studies has been made focus on squint SAR imaging in Near-Space, pointing out that exact expression of synthetic aperture length should be considered under forward-squint mode. Starting from the echo signal itself, a detailed analysis has been derived. Established the algorithm that Range walk removal and Range compression at first, subsequent cubic phase filtering, SRC and RCMC by using NCS, completing azimuth compression and residual phase compensation at last.4. Detailed studies has been made focus on forward-squint SAR motion error in Near-Space. Pointing out that swing error is the main form of lateral error. Expression of error margin has been given of cross track error including constant disturbance velocity and cosine disturbance velocity, as well as lateral error. Analysis of motion compensation has been made. Pointed out that can use constant squint angle instead of instantaneous squint angle of track error, but cannot of lateral error. Finally, a algorithm with motion compensation has been given.