An accelerated chirp scaling algorithm for synthetic aperture imaging

The accelerated chirp scaling (ACS) algorithm is based on the chirp scaling (CS) algorithm, with the difference that the ACS algorithm processes pulse compressed data. To remove the range variant nature of the system impulse response, the ACS algorithm operates by chirp scaling the linear frequency modulated (LFM) signal that already exists in the range-Doppler domain of the pulse compressed data. This LFM signal is commonly compensated for in the CS algorithm and the range-Doppler algorithm by secondary range compression (SRC). Chirp scaling of the uncompensated SRC signal allows the ACS algorithm to operate on pulse compressed data, removing the overhead associated with the processing of data that still contains the LFM transmitted pulse (as is necessary in the CS algorithm). In cases where chirp scaling of the uncompensated SRC chirp does not yield adequate results, a range chirp with a chirp length on the order of the maximum differential range migration across the scene can be inserted into the data, and this new chirp can be scaled during processing.