Method for locating a backscatter-based transponder

Abstract

A method and apparatus for locating a transponder is provided. A carrier signal is transmitted by a base station and a transponder transmits a locating signal that is generated through phase modulation and backscattering of the carrier signal sent by the base station when the transponder is within a transmission range of the base station, whereby the transponder is located on the basis of the locating signal.

1 . A method for locating a transponder, the method comprising the steps of: 
 transmitting a carrier signal by a base station;    transmitting, by the transponder, a locating signal that is generated through phase modulation and backscattering of the carrier signal sent by the base station when the transponder is within a transmission range of the base station; and    locating the transponder on the basis of the locating signal.    
     
     
         2 . The method according to  claim 1 , wherein the base station transmits at least one command to the transponder while the transponder transmits the locating signal.  
     
     
         3 . The method according to  claim 1 , wherein the transponder is a passive transponder, and wherein the transponder transmits the location signal when an operating energy level of the carrier signal is sufficient for supplying the transponder.  
     
     
         4 . The method according to  claim 1 , wherein a selection process is performed by the base station when a plurality of transponders transmit a location signal and a transponder is to be selected from the plurality of transponders.  
     
     
         5 . The method according to  claim 1 , wherein the selection method is an ALOHA method, in particular a slotted ALOHA method.  
     
     
         6 . The method according to  claim 4 , wherein the selection process is a deterministic process, in particular a binary process.  
     
     
         7 . The method according to  claim 1 , wherein the locating signal is generated by modulation with a subcarrier of the carrier signal transmitted from the base station.  
     
     
         8 . The method according to  claim 1 , wherein a memory internal to the transponder contains one or more parameters for setting the locating signal.  
     
     
         9 . The method according to  claim 8 , wherein the one or more parameters are used to set a frequency and/or a duty cycle of a modulation signal with which the carrier signal is modulated.  
     
     
         10 . The method according to  claim 9 , wherein the frequency and/or the duty cycle are derived from an oscillator clock internal to the transponder.  
     
     
         11 . The method according to  claim 1 , wherein the transponder terminates the transmission of the locating signal when a predefinable maximum time has elapsed and/or the transponder receives a command.  
     
     
         12 . The method according to  claim 1 , wherein the transponder is located by an additional base station.  
     
     
         13 . The method according to  claim 1 , wherein a frequency of the carrier signal is in the UHF frequency range.  
     
     
         14 . A method for locating a backscatter-based transponder, the method comprising the steps of: 
 transmitting a locating command via a base station to the transponder;    receiving the locating command by the transponder;    transmitting, by the transponder, a locating signal that is generated by phase modulation and backscattering of a carrier signal transmitted from the base station; and    locating the transponder on the basis of the locating signal.    
     
     
         15 . The method according to  claim 14 , wherein, prior to transmitting the locating command to the transponder, the base station performs a selection process, whereby the transponder to be located is selected from a plurality of transponders.  
     
     
         16 . The method according to  claim 15 , wherein the selection process is an ALOHA method or a slot-based ALOHA method.  
     
     
         17 . The method according to  claim 15 , wherein the selection process is a deterministic method or a binary method.  
     
     
         18 . The method according to  claim 14 , wherein the transponder stops transmitting the locating signal when a predeterminable maximum time period has expired and/or the transponder receives a command.  
     
     
         19 . The method according to  claim 1 , wherein the transponder is a backscatter-based transponder, and wherein the carrier signal transmitted by the base station is an unmodulated carrier signal.  
     
     
         20 . An object location system comprising: 
 a base station for transmitting a carrier signal; and    a transponder being attached or integrated into the object, the transponder identifying the object, the transponder transmitting a locating signal that is generated through phase modulation and backscattering of the carrier signal transmitted by the base station when the transponder is within a transmission range of the base station, the object being located on the basis of the locating signal.