A real‐time correlator has been developed that utilizes successive acousto‐optic interactions in two adjacent piezoelectric crystals (lithium niobate, LiNbO3, and bismuth germanium oxide, BGO) having surface‐acoustic‐wave (SAW) propagation velocities that differ by almost a factor of 2. Complex waveforms, such as FM chirps and Barker codes, have been correlated successfully. A large time‐bandwidth product (∼3000) was obtained, and a 40‐dB dynamic range was shown to be feasible. The use of this two‐crystal device to obtain either pulse expansion or time inversion of a signal also was demonstrated.