Dynamic signal detection threshold
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.
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.