A feasibility study of the synchronous and asynchronous operation of a SAW programmable correlator based on a SAW convolver

A feasibility study of using a SAW (surface acoustic waves) convolver as a programmable correlation is described. The transformation of the convolver with one of its inputs being time-inverted, into a correlator is discussed. This programmable SAW correlator can operate in two modes: (a) For the synchronous operation, the two inputs to be correlated can be unknown and the required time-inverted replica of one of the inputs is achieved by using SAW time-inversion system. Thus, the correlation between any, almost simultaneous, two inputs of limited time duration can be attained. (b) For the asynchronous operation, the reference input has to be time-inverted and periodic. A correlation between this reference and any input (of any time duration and at any arrival time) can be performed. The principles of operations of the programmable correlator are demonstrated throughout an experimental system using off-the-shelf devices. While the described experimental system exhibits a relatively modest performance (since we used devices with small time-bandwidth product), it can usefully demonstrate how such a correlator operates in both modes. Of course, using a state-of-the art SAW convolver together with RAC (reflective array compression) and chirp filters for the required time-inversion/scaling, the proposed programmable correlator can have a time-bandwidth product in the order of thousands.