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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
First Claim
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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, andmeans 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.

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