Background object sensor

1. A system, comprising:

an RFID transmitter positioned about one side of a portal, wherein the RFID transmitter is configured to transmit a first radio frequency signal and a second radio frequency signal in a monitored region;

an RFID receiver positioned about another side of the portal, wherein the RFID receiver is configured to receive the first radio frequency signal and the second radio frequency signal, the first radio frequency signal reflecting off of a surface of an object to be monitored and the second radio frequency signal not reflecting off of the surface of the object to be monitored;

a comparator configured to compare the first radio frequency signal with the second radio frequency signal to provide a signal comparison; and

a processor configured to determine, based on the signal comparison, whether the object to be monitored has been positioned in the monitored region.

2. The system of claim 1 , wherein the processor is further configured to determine whether the object to be monitored is in motion in accordance with the signal comparison.

3. The system of claim 2 , wherein the processor is further configured to determine whether the object to be monitored is in motion in accordance with a continuous fluctuation of the second radio frequency signal.

4. The system of claim 3 , wherein the processor is further configured to determine whether the object to be monitored is no longer in motion in accordance with an ending of the continuous fluctuation of the second radio frequency signal.

5. The system of claim 1 , wherein at least one of the first and second radio frequency signals is a simulated electronic product code signal.

6. The system of claim 1 , wherein the comparator is further configured to compare received signal strengths.

7. The system of claim 6 , wherein a received signal strength of the first radio frequency signal comprises a first sum of signal strengths of a plurality of component signals received by the RFID receiver.

8. The system of claim 7 , wherein a received signal strength of the second radio frequency signal comprises a second sum of signal strengths equal to the first sum of signal strengths and at least one additional signal strength corresponding to a radio frequency signal reflected off the object to be monitored.

9. The system of claim 6 , wherein the comparator is further configured to compare a received signal strength of at least one of the first and second radio frequency signals in accordance with a plurality of time samples.

10. The system of claim 1 , wherein the comparator is further configured to compare signal phase information.

11. The system of claim 10 , wherein the processor is further configured to determine a signal phase of at least one of the first and second radio frequency signals in accordance with a plurality of time samples.

12. The system of claim 1 , further comprising a tag inventory performed by the RFID reader.

13. The system of claim 12 , wherein the first radio frequency signal comprises a signal with a power level of approximately 30 dBm and the second radio frequency signal comprises a signal with a power level less than approximately −5 dBm.

14. The system of claim 12 , further comprising an interleaving of the comparing and a plurality of tag inventories.

15. The system of claim 1 , wherein the processor is further configured to determine a distance to the object to be monitored in accordance with the signal comparison.

16. The system of claim 15 , wherein the processor is further configured to determine a threshold received signal strength and the distance to the object to be monitored in accordance with the threshold received signal strength.

17. A method, comprising:

positioning an RFID transmitter about one side of a portal;

transmitting, via the RFID transmitter, a first radio frequency signal and a second radio frequency signal in a monitoring region;

positioning an RFID receiver about another side of the portal;

receiving, via the RFID receiver, the first radio frequency signal and the second radio frequency signal, the first radio frequency signal reflecting off of a surface of an object to be monitored and the second radio frequency signal not reflecting off of the surface of the object to be monitored;

comparing the first radio frequency signal with the second radio frequency signal to provide a signal comparison; and

determining, based on the signal comparison, whether the object to be monitored has been positioned in the monitored region.

18. The method of claim 17 , further comprising determining whether the object to be monitored is in motion in accordance with the signal comparison.

19. A system, comprising:

an RFID transmitter positioned about one side of a portal, wherein the RFID transmitter is configured to transmit a first radio frequency signal and a second radio frequency signal in the monitored region;

an RFID receiver positioned about another side of the portal, wherein the RFID receiver is configured to receive the first radio frequency signal and the second radio frequency signal, the first radio frequency signal reflecting off of a surface of the object to be monitored and the second radio frequency signal not reflecting off of the surface of the object to be monitored; and

a processor configured to determine, based on a signal comparison of the first radio frequency signal and the second frequency signal, whether the object to be monitored is positioned in the monitored region.

20. The system of claim 19 , wherein the processor is further configured to determine whether the object to be monitored is in motion in accordance with the signal comparison.