Passive transponders using acoustic surface wave devices

• US 4,059,831 A
• Filed: 10/06/1975
• Issued: 11/22/1977
• Est. Priority Date: 10/06/1975
• Status: Expired due to Term

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Epstein, Max
• Primary Examiner(s): Tubbesing, T.H.
• Assistant Examiner(s): Blum, T. M.
• Application Number:
  US05/617,251
• Time in Patent Office: 778 Days
• Field of Search: 343/6.5 SS, 343/6.8 R, 333/30 R
• US Class Current: 342/44
• CPC Class Codes: G01S 13/755 using delay lines, e.g. acoustic delay lines

Abstract

A passive transponder sensitive to electromagnetic pulses received in the form of surface acoustic waves. The device utilizes a plurality of interdigital transponders each consisting of a metallic deposit on a piezoelectric substrate and serving as an electrode. Transponder deactivation and energy interruption means provide programability and coding.

Claims

1. A transponder for receiving and for retransmitting pulsed electromagnetic energy characterized by a frequency range of from about 10 meg. Hz to 1000 meg. Hz and comprising:

antenna means for receiving and for transmitting a signal of said pulsed electromagnetic energy,

peizoelectric substrate means remote from said antenna means,

electrode means carried as an array of electrodes on said peizoelectric substrate means to define therewith an acoustic surface wave device, said device including a plurality of interdigital transducers,

electrical energy conducting means interconnecting said antenna means with at least one of said interdigital transducers,

said transducers and said substrate means constituting means responsive to a signal received by said transducers from said antenna means to effect a finite time delay in the conductive travel of said signal along said piezoelectric substrate means, thereby to provide a time-delayed signal,

said transducers constituting means for transmitting the time-delayed signal to said antenna means,

said transducers including a circular input transducer propagating radially and an array of output taps disposed in cyclical succession about said transducer,

said output taps being disposed on a circumference of a circular pattern, and

means connecting at least one of said output taps to said antenna means,

whereby said transducers obviate bi-directional radiation and are compatible with each other.

2. A transponder for receiving and for retransmitting pulsed electromagnetic energy characterized by a frequency range of from about 10 meg. Hz to 1000 meg. Hz and comprising:

means for receiving and for transmitting a signal of said pulsed electromagnetic energy,

piezoelectric substrate means,

electrode means carried as an array of electrodes on said piezoelectric substrate means to define therewith an acoustic surface wave device, said device including a plurality of interdigital transducers, electrical energy conducting means interconnecting said means for receiving and transmitting a signal with at least one of said interdigital transducers.

said transducers and said substrate means constituting means responsive to a signal received by said transducers to effect a finite time delay in the conductive travel of said signal along said piezoelectric substrate means, thereby to provide a time-delayed signal,

said transducers constituting means for transmitting the time-delayed signal,

programming means to program said transducers, said programming means consisting essentially of means to inactivate selectively at least one of said transducers by preventing surface wave travel in a zone adjacent thereto,

said means to deactivate a transducer comprising pad means overlying said substrate means in a zone adjacent a transducer,

whereby pressure applied to said substrate means through said pad means renders said substrate means nonconductive to a surface acoustic wave.

3. The structure as set forth in claim 2 wherein said transducers include a tapped interdigital transducer consisting essentially of spaced taps defining a delay line, and wherein said spaced taps are separated mechanically from one another a distance at least equal to the length of an interrogating r.f. pulse applied thereto.

4. A transponder for receiving and for retransmitting pulsed electromagnetic energy characterized by a frequency range of from about 10 meg. Hz to 1000 meg. Hz and comprising:

means for receiving and for transmitting a signal of said pulsed electromagnetic energy,

piezoelectric substrate means,

electrode means carried as an array of electrodes

on said piezoelectric substrate means to define therewith an acoustic surface wave device, said device including a plurality of interdigital transducers,

said transducers and said substrate means constituting means responsive to a signal received by said transducers to effect a finite time delay in the conductive travel of said signal along said piezoelectric substrate means, thereby to provide a time-delayed signal,

said transducers constituting means for transmitting the time-delayed signal,

programming means to program said transducers,

said programming means consisting essentially of pressure means to inactivate selectively at least one of said transducers by preventing surface wave travel in a zone adjacent thereto.

said means to inactivate one of said transducers comprising means selective to connect and disconnect said transducers.