Patent ID: 8207887

Claim:
A method of processing radar data obtained from a platform which is subjected to non-uniform movement, the distance the platform travels during the formation of an image comprising an aperture; the method comprising: building up a predetermined number of average pulses; each representing a single point on the aperture; the building of each average pulse comprising: inputting radar data from a radar antenna; passing the radar signal through low noise amplifier to reduce impact of electronic noise from the radar system; down converting the signal with a mixer to obtain a lower frequency; filtering out harmonics from the higher frequency range; sampling the radar data using an analog to digital converter at at least the Nyquist down range frequency; based upon the IF of the radar; determining a scene center (center of SAR imagery) for the purpose of motion compensation; performing a two stage averaging scheme of the received signals with a variable window function; determining a window function based upon the velocity and acceleration of the platform and scene center; the window function comprising a first stage window; coherently averaging N pulses together to create an average pulse; compensating to the scene center by multiplying by a complex exponential based upon both the GPS and inertial navigational system; performing an inverse Fourier transform; phase correcting for quadratic errors depending on frequency; summing the average pulses using low pass filter; repeating the step of building up an average pulse for a first predetermined number of times for a time period that is less than the Nyquist sample time interval; performing a two dimensional inverse Fourier transform using the predetermined number of average pulses to obtain at least one SAR image.