a non - coherent technique employs a zero padded fft for the fast acquisition of direct sequence spread spectrum signals in the presence of large doppler shifts . the application of a fft to code acquisition results in decreased acquisition time , and can improve the probability of detection . a set of partial correlators and a zero padded fft are used to reduce the search region for code acquisition while maintaining good frequency resolution for doppler offset . this approach will prove most pertinent in future reconfigurable terminals .