Time of arrival delay cancellations

• US 20150061920A1
• Filed: 04/28/2014
• Published: 03/05/2015
• Est. Priority Date: 08/30/2013
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Pahlavan, Kourosh, Eskafi, Farokh Hassanzadeh
• Granted Patent: US 9,702,970 B2
• Time in Patent Office: Days
• US Class Current: 342/125
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236

Abstract

The invention relates to a ranging system for measuring the distance between an interrogator and a transponder. The transponder includes: a signal receiver for receiving a challenge signal from an interrogator; a signal processor for processing the challenge signal and generating a response signal in response to the challenge signal; a buffer for storing the response signal generated by the signal processor; and a signal transmitter for sending the response signal stored in the buffer when the signal processor receives a ranging signal from the interrogator, wherein a time interval between the challenge signal and the ranging signal is known to both transponder and the interrogator.

Claims

1. A transponder of a ranging system, comprising:

a signal receiver for receiving a challenge signal from an interrogator;

a signal processor for processing the challenge signal, generating a response signal in response to the challenge signal and storing the response signal; and

a signal transmitter for sending the response signal in response to a ranging signal from the interrogator,

wherein there is a time interval between the challenge signal and the ranging signal.

2. A transponder as recited in claim 1, wherein the time interval is known to both transponder and the interrogator.

3. A transponder as recited in claim 1, wherein the time interval is equal to or longer than a time interval required for the signal processor to process the challenge signal, generate the response signal and store the response signal.

4. A transponder as recited in claim 1, wherein the time interval is a secret between the transponder and the interrogator.

5. A transponder as recited in claim 1, wherein the ranging signal includes a secret between the transponder and the interrogator.

6. A transponder as recited in claim 1, wherein the signal transmitter is adapted to send a start-of-session signal to initiate a communication session with the interrogator.

7. A transponder as recited in claim 1, wherein the interrogator is included in a vehicle and the transponder is carried by an authorized user of the vehicle.

8. An interrogator of a ranging system, comprising:

a signal transmitter for sending a challenge signal and, after a time interval, sending a ranging signal to a transponder;

a signal receiver for receiving a response signal from the transponder; and

a signal processor for determining a time of flight based on the ranging and response signals to thereby calculate a distance between the interrogator and the transponder.

9. An interrogator as recited in claim 8, wherein the time interval is known to both transponder and the interrogator.

10. An interrogator as recited in claim 8, wherein the time interval is equal to or longer than a time interval required for the transponder to process the challenge signal and the response signal.

11. An interrogator as recited in claim 8, wherein the time interval is a function of the response signal.

12. An interrogator as recited in claim 8, wherein the interrogator is adapted to calculate an expected response signal and compare the expected response signal to the response signal received from the transponder.

13. An interrogator as recited in claim 8, wherein the time interval is a secret between the transponder and the interrogator.

14. An interrogator as recited in claim 8, wherein the ranging signal includes a secret between the transponder and the interrogator.

15. A ranging system, comprising:

an interrogator for sending a challenge signal and, after a time interval, sending a ranging signal; and

a transponder for receiving and processing the challenge signal, generating a response signal in response to the challenge signal, storing the response signal and, in response to the ranging signal, sending the response signal to the interrogator,

wherein the interrogator is adapted to determine a time of flight based on the ranging and response signals to thereby calculate a distance between the interrogator and the transponder.

16. A ranging system as recited in claim 15, wherein the time interval is known to both transponder and the interrogator.

17. A ranging system as recited in claim 15, wherein the time interval is a secret between the transponder and the interrogator.

18. A ranging system as recited in claim 15, wherein the time interval is equal to or longer than a time interval required for the transponder to process the challenge signal and the response signal.

19. A ranging system as recited in claim 15, wherein the interrogator is adapted to calculate an expected response signal.

20. A ranging system as recited in claim 15, wherein the interrogator is adapted to compare the expected response signal to the response signal sent by the transponder.

21. A ranging system as recited in claim 15, wherein the time interval is a function of the response signal.

22. A ranging system as recited in claim 15, wherein the ranging signal includes a secret between the transponder and the interrogator.

23. A ranging system as recited in claim 15, wherein the interrogator is included in a vehicle and the transponder is carried by an authorized user of the vehicle.

24. A method for operating a ranging system, comprising:

causing a transponder to receive a challenge signal from an interrogator, to generate a response signal in response to the challenge signal and store the response signal;

causing the transponder to receive a ranging signal from the interrogator upon lapse of a time interval from receipt of the challenge signal; and

causing the transponder to send the stored response signal to the interrogator in response to the ranging signal.

25. A method as recited in claim 24, wherein the time interval is known to both the transponder and the interrogator

26. A method as recited in claim 24, wherein the time interval is a secret between the transponder and the interrogator.

27. A method as recited in claim 24, wherein the time interval is equal to or longer than a time interval required for the transponder to process the challenge signal and the response signal.

28. A method as recited in claim 24, further comprising, prior to the step of receiving a challenge signal from an interrogator:

determining the time interval as a function of the response signal.

29. A method as recited in claim 24, further comprising:

causing the interrogator to calculate an expected response signal and to determine whether the expected response signal is same as the response signal from the transponder; and

causing the interrogator to determine a time of flight based on the challenge and response signals to thereby determine a distance between the interrogator and the transponder.

30. A method as recited in claim 24, further comprising:

causing the transponder to send a start-of-session signal to thereby initiate a communication session.

31. A method as recited in claim 24, wherein the ranging signal includes a secret between the transponder and the interrogator.