Electronic quasi-passive identification system

Abstract

A quasi-passive identification system having an interrogator and a passiveransponder. The interrogator has a signal generator that generates radio-frequency energy under the control of a manual actuator. A preset encoder encodes the radio-frequency energy with an interrogation code to produce an interrogation signal that is radiated by an antenna. The transponder has an receiver for receiving the interrogation signal and separating it into received radio-frequency energy and a coded signal. A decoder decodes the coded signal and looks for a match between the coded signal and the interrogation code. A response transmitter, which is controlled by the decoder, encodes the received radio-frequency energy with the response code and radiates the response signal. When a receiver in the interrogator receives the response signal, the response signal is decoded and analyzed for a proper response. A response indicator is energized when a proper response is received.

What is claimed is: 
     
       1. A quasi-passive identification system comprising: an interrogator having a signal generator means for generating radio-frequency energy, an interrogation encoder means for encoding said radio-frequency energy with an interrogation code to produce an interrogation signal, an interrogation transmit means for radiating said interrogation signal, and a response receive means for receiving radio-frequency signals; and   a transponder having an interrogation receive means for receiving radio-frequency signals and separating said radio-frequency signals into received radio-frequency energy and a coded signal, an interrogation decoder means for decoding said coded signal, and a response transmit means controlled by said interrogation decoder means for encoding said received radio-frequency energy with a response code to produce said response signal and for radiating said response signal.   
     
     
       2. The system of claim 1 wherein said interrogator includes an actuate means for triggering said interrogator to radiate said interrogation signal. 
     
     
       3. The system of claim 2 wherein said actuate means is connected to said signal generator means for permitting manual actuation of said interrogator by energizing said signal generator means. 
     
     
       4. The system of claim 1 wherein said response receive means includes a response decoder means for decoding said received radio-frequency signals to detect the presence of said response code therein. 
     
     
       5. The system of claim 4 wherein said interrogator includes a preset means for inputting said interrogation code into said interrogation encoder means and for inputting said response code into said response decoder means. 
     
     
       6. The system of claim 5 wherein said interrogator further includes an indicator means responsive to said response decoder means for indicating the presence of said response code. 
     
     
       7. The system of claim 6 wherein said interrogator includes an actuate means for triggering said interrogator to radiate said interrogation signal. 
     
     
       8. The system of claim 7 wherein said actuate means is connected to said signal generator means for permitting manual actuation of said interrogator by energizing said signal generator means. 
     
     
       9. The system of claim 8 wherein said transponder includes an energy dissipation means, and said response transmit means includes a radio-frequency transmission switch means responsive to said interrogation decoder means for transmitting said received radio-frequency energy to said energy dissipation means when a predetermined interrogation signal is not detected by said interrogation decoder means. 
     
     
       10. The system of claim 9 wherein said response transmit means further includes a frequency shift means connected to said switch means for changing the frequency of said radio-frequency energy before encoding said received radio-frequency energy with a response code. 
     
     
       11. The system of claim 10 wherein said frequency shift means is a frequency doubler. 
     
     
       12. The system of claim 11 wherein said transponder includes a preset means for inputting said interrogation code into said interrogation decoder means and for inputting said response code into said response encoder means. 
     
     
       13. A passive transponder, for use in responding to a radio-frequency input signal modulated with a proper interrogation code, comprising: a receive means for receiving radio-frequency input signals and separating said input signals into radio-frequency energy and a coded signal;   a decoder means connected to said receive means for decoding said coded signal and producing an output if said coded signal matches said interrogation code; and   a transmit means responsive to said output of said decoder means for encoding said radio-frequency energy with a response code and for radiating said energy as a response signal.   
     
     
       14. The transponder of claim 13 further including an energy dissipation means, and wherein said transmit means includes a radio-frequency transmission switch means for transmitting said radio-frequency energy to said energy dissipation means when said coded signal does not match said interrogation code. 
     
     
       15. The transponder of claim 14 wherein said transmit means further includes a frequency shift means connected to said switch means for changing the frequency of said radio-frequency energy before encoding said received radio-frequency energy with a response code. 
     
     
       16. The transponder of claim 15 wherein said frequency shift means is a frequency doubler. 
     
     
       17. The transponder of claim 16 further including a preset means for inputting said interrogation code into said decoder means and for inputting said response code into said transmit means.