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Microwave noncontact identification transponder using subharmonic interrogation and method of using the same

  • US 5,525,993 A
  • Filed: 05/12/1995
  • Issued: 06/11/1996
  • Est. Priority Date: 05/12/1995
  • Status: Expired due to Fees
First Claim
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1. An improvement in a contactless transponder having a modulation oscillator, a quasi-optical mixer having a first input coupled to said modulation oscillator and an antenna having an input coupled to an output of said mixer comprising:

  • an identification code generator coupled to a second input of said mixer, wherein said mixer modulates an interrogation signal received by said antenna having a frequency, fi, with a data carrier signal having a frequency, fd, generated by said modulation oscillator to transmit supressed-carrier double sideband response signals, wherein each sideband response signal is modulated by an identification code generated by said identification code generator, said data frequency, fd, being at a nonharmonic value of said interrogation frequency, fi,whereby false detection arising from reflections of transmitted harmonics of said interrogation signal is avoided.

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