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Transponder in communication system

  • US 20050134434A1
  • Filed: 01/11/2005
  • Published: 06/23/2005
  • Est. Priority Date: 08/19/2002
  • Status: Active Grant
First Claim
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1. A transponder of a communication system wherein an interrogator transmits a main carrier, and the transponder receives said main carrier through an antenna, and effects a predetermined modulation of said main carrier by changing an impedance of a circuit connected to said antenna, as viewed from said antenna, to generate a reflected wave for responding to said interrogator, wherein an improvement comprises:

  • said circuit including a switching element operable to modulate said main carrier received by said antenna, and an impedance element connected to said switching element; and

    said impedance element having an impedance determined so as to provide a predetermined difference between a phase of a total impedance which is a sum of an input impedance of said antenna and an impedance of said circuit, at a frequency of said main carrier, when said switching element is in an on state, and that when the switching element is in an off state.

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