A large-range autofocus microwave photonic radar based on adaptive spatial filtering along the range direction

A large-range autofocus microwave photonic radar based on adaptive spatial filtering along the range direction is proposed to achieve high-resolution imaging of the target at any distance. By firstly estimating the target distance and then adaptively adjusting the coverage of the spatial filter, the targets at any distance can be filtered out and their high-resolution images can be achieved. Besides, the sampling rate of the back-end ADC can be as low as hundreds of megahertz, leading to low computation load. Comparing to the present microwave photonic radars, new radar structure and work flow are proposed to achieve high-resolution imaging of the targets at any distance. The range window is not limited and the computation load is low, which is hard to realize by the present microwave photonic radars. Experimentally, a K-band (18-26 GHz) autofocus radar is established, the large-range autofocus ability is verified by autofocusing and high-resolution imaging for a static metallic plane at the equivalent distances of 790 m, 3.97 km and 8.11 km, respectively. Imaging for a flying UAV also indicates the system's high-resolution imaging ability for the moving target. The proposed system enhances the capabilities of microwave photonic radars and has the potential to be applied in non-cooperative target identification.