System and method for identifying objects

Abstract

A system and method for identifying objects. A preferred embodiment employs a radio transceiver on each object. Each article is identified by recording a condition of an interrogation signal at a time in which the respective transceiver exhibits a nonlinearity.

What is claimed is:  
     
         1 . In a system including a transmitter that transmits an interrogation signal, and a plurality of articles each having a respective circuit for transmitting a respective circuit signal responsive to the interrogation signal, the circuit signal having a nonlinearity, a method comprising the steps, performed for each circuit, of: 
 detecting the nonlinearity;    recording a condition of the interrogation signal, responsive to the previous step; and    using the recorded condition to access a record for the circuit.    
     
     
         2 . The method of claim I wherein the condition includes an amplitude.  
     
     
         3 . The method of claim I further including recording a plurality of digits in the record.  
     
     
         4 . The method of  claim 3  wherein each digit corresponds to a respective frequency.  
     
     
         5 . The method of claim I wherein detecting the nonlinearity includes causing an interrogation signal to have a first interrogation signal frequency at a first time, and the method further includes 
 detecting a plurality of digits includes by causing the interrogation signal to have other interrogation signal frequencies at a time different than the first time.    
     
     
         6 . An apparatus for a system including a transmitter that transmits an interrogation signal, and a plurality of articles each having a respective circuit for transmitting a respective circuit signal responsive to the interrogation signal, the circuit signal having a nonlinearity, the apparatus comprising: 
 a detector that detects, for each circuit, the nonlinearity;    a recorder that records a condition of the interrogation signal, in response to an output of the detector; and    an allocator that allocates a respective record for each circuit, the record being accessible by the recorded condition.    
     
     
         7 . The apparatus of  claim 6  further including logic that records a plurality of digits in the record.  
     
     
         8 . The apparatus of  claim 7  further including logic that detects the plurality of digits, by causing an interrogation signal to have a plurality of interrogation signal frequencies.  
     
     
         9 . An apparatus for a system including a transmitter that transmits an interrogation signal, and a plurality of articles each having a respective circuit for transmitting a respective circuit signal responsive to the interrogation signal, the circuit signal having a nonlinearity, the apparatus comprising: 
 means for detecting the nonlinearity;    means for recording a condition of the interrogation signal, responsive to the previous means; and    means for accessing a record for a circuit by using the recorded condition.    
     
     
         10 . The apparatus of  claim 9  further including an allocator that allocates a record responsive to an output of the means for detecting.  
     
     
         11 . The apparatus of  claim 9  further including logic that records a plurality of digits in the record.  
     
     
         12 . The apparatus of  claim 11  further including logic that detects the plurality of digits, by causing an interrogation signal to have a plurality of interrogation signal frequencies.