Maximally flat frequency coded (mffc) passive wireless saw rfid tags and sensors

A surface acoustic wave device responsive to an interrogation signal for producing a return signal, the surface acoustic wave device comprising:

• an antenna for receiving the interrogation signal;
• a piezoelectric substrate;
• one or more frequency selective reflective arrays formed on the piezoelectric substrate;
• a first interdigital transducer responsive to the interrogation signal for launching a surface acoustic wave on the substrate responsive thereto, the surface acoustic wave propagating to the one or more frequency selective reflective arrays;
• a second interdigital transducer;
• a reflected surface acoustic wave reflected from each one of the frequency-selective reflective arrays to the second interdigital transducer;
• and
• the second interdigital transducer producing the return signal responsive to each reflected surface acoustic wave.

A surface acoustic wave system comprising a plurality of surface acoustic wave devices, each surface acoustic wave device comprising a

• an antenna for receiving the interrogation signal;
• a piezoelectric substrate;
• one or more frequency-selective reflective arrays disposed on the piezoelectric substrate;
• an interdigital transducer for launching a surface acoustic wave on the substrate, the surface acoustic wave propagating to the one or more frequency-selective reflective arrays;
• a reflected surface acoustic wave reflected from each one of the frequency-selective reflective arrays;
• the interdigital transducer receiving each of the reflected surface acoustic waves;
• the return signal, responsive to each reflected surface acoustic wave, formed at the interdigital transducer array;
• and
• wherein each one of the plurality of surface acoustic wave devices has an impulse response with a different delay path to a first reflective array of each one of the plurality of surface acoustic wave devices, thereby shifting an impulse response of each one of the plurality of surface acoustic wave devices by a different increment of time.