Dynamic signal detection threshold

• US 8,774,710 B2
• Filed: 06/21/2011
• Issued: 07/08/2014
• Est. Priority Date: 07/01/2010
• Status: Active Grant

• Current Assignee: Zest Labs, Inc.
• Original Assignee: Intelleflex Corporation
• Inventors: Kawaguchi, Dean, Rao, Manu H. R.
• Primary Examiner(s): NGUYEN, TUAN HOANG
• Application Number:
  US13/165,754
• Publication Number:
  US 20120003938A1
• Time in Patent Office: 1,113 Days
• Field of Search: 455/39, 455/41.1, 455/41.2, 455/63.1, 455/67.13, 375/324
• US Class Current: 455/39
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: H04Q 2213/13095 PIN / Access code, authentication

Abstract

A method for setting a signal detection threshold according to one embodiment includes determining a measure of a noise floor in a signal derived from a radio frequency signal received by an antenna using a same circuit used to detect a subcarrier signal during transmitting and prior to sending a command to a transponder to respond; and setting a signal detection threshold above the noise floor. Such methodology may also be implemented as a system using logic for performing the various operations. Additional systems and methods are also presented.

Claims

1. A method for setting a signal detection threshold, the method comprising:

transmitting an outgoing signal;

determining a measure of a noise floor in a signal derived from a radio frequency signal received by an antenna during the transmitting and prior to sending a command to a transponder to respond, the determining being performed using a same circuit used to detect a subcarrier signal; and

setting a signal detection threshold above the noise floor.

2. The method of claim 1, wherein the determining and setting are performed continuously.

3. The method of claim 1, wherein the determining and setting are performed after each frequency hop.

4. The method of claim 1, further comprising performing carrier cancellation during sending the outgoing signal and prior to determining the measure of the noise floor.

5. The method of claim 1, wherein the determining is performed when no signal is received from the transponder.

6. The method of claim 1, wherein noise in the radio frequency signal received by an antenna is primarily reflections of the outgoing signal.

7. A method for setting a signal detection threshold, the method comprising:

determining a measure of a noise floor in a signal derived from a radio frequency signal received by an antenna using a same circuit used to detect a subcarrier signal during transmitting and prior to sending a command to a transponder to respond;

setting a signal detection threshold above the noise floor; and

detecting a subcarrier signal in the signal based on the signal detection threshold, and outputting a subcarrier power detect signal.

8. The method of claim 7, wherein the subcarrier signal is derived from a sideband portion of a backscattered signal.

9. The method of claim 7, wherein a subcarrier detect module detects the subcarrier signal and outputs the subcarrier power detect signal, wherein the subcarrier detect module includes:

a scaler module for scaling baseband signals;

a complex to magnitude module receiving output from the scaler;

a leaky integrator receiving output from the complex to magnitude module; and

a subcarrier power detect signal output coupled to the leaky integrator.

10. A system for setting a signal detection threshold, the system comprising:

logic configured to cause transmission of an outgoing signal;

logic configured to determine a measure of a noise floor in a signal derived from a radio frequency signal received by an antenna during transmitting the outgoing signal and prior to sending a command to a transponder to respond, the determining being performed using a same circuit used to detect a subcarrier signal; and

logic configured to set a signal detection threshold above the noise floor.

11. The system of claim 10, wherein the logic configured to determine and setting is adapted to operate continuously.

12. The system of claim 10, wherein the logic configured to set is adapted to set the signal detection threshold after each frequency hop.

13. The system of claim 10, further comprising logic configured to perform carrier cancellation prior to determining the measure of the noise floor.

14. The system of claim 10, further comprising at least one antenna for receiving the radio frequency signal.

15. The system of claim 10, wherein the logic configured to determine determines the measure of the noise floor when no signal is received from the transponder.

16. The system of claim 10, wherein noise in the radio frequency signal received by an antenna is primarily reflections of the outgoing signal.

17. A system for setting a signal detection threshold, the system comprising:

logic configured to determine a measure of a noise floor in a signal derived from a radio frequency signal received by an antenna using a same circuit used to detect a subcarrier signal during transmitting and prior to sending a command to a transponder to respond;

logic configured to set a signal detection threshold above the noise floor; and

logic configured to detect a subcarrier signal in the signal based on the signal detection threshold, and logic for outputting a subcarrier power detect signal.

18. The system of claim 17, wherein the subcarrier signal is derived from a sideband portion of a backscattered signal.

19. The system of claim 17, wherein a subcarrier detect module detects the subcarrier signal and outputs the subcarrier power detect signal, wherein the subcarrier detect module includes:

a scaler module for scaling baseband signals;

a complex to magnitude module receiving output from the scaler;

a leaky integrator receiving output from the complex to magnitude module; and

a subcarrier power detect signal output coupled to the leaky integrator.