A new mode of operation for the surface-wave convolver

A new mode of operation for the surface-acoustic-wave convolver has been discovered. The features of this mode are as follows. 1) It is a degenerate mode, but is detected by an interdigital transducer whose periodicity bears no special relationship to the input transducers. 2) It operates only in an interaction region with bi-directional surface wave amplification. 3) It is more efficient than the usual nondegenerate mode which can operate on the same device. 4) It makes possible highly efficient surface wave convolution with significantly lower spurious response than the usual nondegenerate mode. This device consists of a substrate of YZ LiNbO3with a film overlay of CdSe in the interaction region. A dc bias field applied across the electrodes of the output structure provides the bidirectional surface-wave amplification. The device has been used to process PN codes with time-bandwidth products up to 280.