Near range MMW synthetic aperture radiometer 3D passive imaging

Millimeter wave synthetic aperture radiometer (MMW-SAR) technology can use phase information of electromagnetic wave radiating from target, and will be real-time imaging with less receiver elements. However MMW-SAR is limited to 2D imaging due to passive regime nowadays, lack of range information of target, which is very unfavorable for target detection and identification, thus this paper presents novel principle and algorithm for MMW-SAR 3D passive imaging under near range conditions. In near range, it is spherical wave radiation and wave front curvature of spherical wave is inversely proportional to propagation distance, synthetic aperture technology can get the curvature of the wave front. Thus there is quadratic phase factor in imaging formula primarily. Regarding the factor as LFM, the 3D imaging algorithm calculates the slope of LFM so as to get wave front curvature, then calculated range distribution. MMW-SAR 3D passive imaging can get both range distribution and brightness temperature distribution, which could effectively overcome fuzzy problem caused by defocus.