Surface acoustic wave chirp filter

A method of synthesizing chirp signals in a surface acoustic wave (SAW) device having a piezoelectric substrate, and array of broadband, point-source, parallel input transducers and an array of output transducers, the method comprising the steps of:

• spacing the input transducers with respect to a first output transducer located at a primary focal point such that the differential distances of the transducers from the primary focal point changes linearly from transducer to adjacent transducer, at a rate corresponding to a first selected linear chirp rate;
• positioning a second output transducer on an arc through the primary focal point, such that the differential distances of the input transducers with respect to the second output transducer change linearly, from input transducer to input transducer, at a rate corresponding to a second selected chirp rate;
• positioning additional output transducers on the same arc through the primary focal point, such that the differential distances of the input transducers to respective additional output transducers change linearly, from input transducer to input transducer, at rates corresponding to additional selected chirp rates;
• applying a pulse signal to at least one of the output transducers;
• and
• obtaining from the input transducers at least one chirp signal at a desired chirp rate corresponding to the selected of output transducers for application of the pulse signal.

A surface acoustic wave (SAW) chirp signal processor, comprising:

• a piezoelectric substrate;
• an array of broadband, point-source input transducers connected in parallel, disposed on the substrate and connected to receive a chirp input signal having an unknown linear chirp rate;
• a first output transducer disposed on the substrate at a primary focal point to receive acoustic signals from the point-source input transducers, wherein the input transducers are positioned such that he differential distances of the input transducers with respect to the primary focal point increase linearly, from input transducer to input transducer, at a rate corresponding to a first selected linear chirp rate, and wherein the first output transducer produces an output pulse only when the unknown linear chirp rate is approximately equal to the selected chirp rate;
• a second output transducer, disposed on the substrate at a point displaced from the first output transducer, such that the differential distances of the input transducers with respect to the second output transducer increase linearly, from input transducer to input transducer, at a rate corresponding to a second selected linear chirp rate, and wherein the second output transducer produces an output pulse only when the unknown linear chirp rate is approximately equal to the second selected chirp rate;
• and
• additional output transducers, disposed on the substrate at points further displaced from the first output transducer, such that the differential distances of the input transducers from respective additional output transducers increase linearly, from input transducer to input transducer, at rates corresponding to additional selected chirp rates, and wherein each of the output transducers produces an output pulse only in response to in input chirp signal within a specific narrow range of chirp rates.