Interrogator and interrogation system employing the same
An interrogator, methods of discerning the presence of an object, and interrogation systems employing the same. In one embodiment, the interrogation systems include multiple interrogators that communicate with a base command unit to track a location of an object. In another embodiment wherein the object is an RFID object (e.g., an object with an RFID tag), the interrogators employ signal processing techniques such as precharging the RFID object, and correlating a reference code with a reply code from the RFID object using selected techniques to increase a sensitivity of the interrogator, especially for adverse environments. In other embodiments, the interrogation systems include variations of metal instruments and sponges employed therewith. In yet another embodiment, the interrogation system includes metal interrogators capable of discerning the presence of a metal object, especially in a presence of another metal object.
1. An interrogator, comprising:
an antenna having a coil that defines an area;
a metal sensing subsystem configured to transmit a pulse to said coil and receive a response therefrom; and
a control and processing subsystem configured to estimate and subtract a background signal level from said response from said coil and provide a residual therefrom, thereby discerning a presence of a metal object in said area.
2. The interrogator as recited in claim 1 wherein said antenna is an antenna array and said coil is one of a plurality of overlapping coils of said antenna array.
3. The interrogator as recited in claim 1 wherein said background signal level comprises a background metal object proximate said metal object.
4. The interrogator as recited in claim 1 wherein said response is a decaying eddy current response.
5. The interrogator as recited in claim 1 wherein said metal sensing subsystem comprises a transmit pulse generator configured to transmit said pulse.
6. The interrogator as recited in claim 1 wherein said metal sensing subsystem comprises a receiver configured to receive said response and provide a sampled response to said control and processing subsystem, said control and processing subsystem configured to estimate and subtract said background signal level from said sampled response.
7. The interrogator as recited in claim 1 wherein said control and processing subsystem comprises a multi-sample noise reduction subsystem, an intra-sample noise reduction subsystem and a detection subsystem.
8. The interrogator as recited in claim 1 wherein said antenna is an antenna array having a plurality of coils and said control and processing subsystem is configured to estimate said background signal level for said coil by averaging responses from a plurality of coils.
9. The interrogator as recited in claim 1 wherein said control and processing subsystem is configured to subtract said background signal level point by point from said response.
10. The interrogator as recited in claim 1 wherein said control and processing subsystem is configured to normalize an integral value of said residual.
11. A method of operating an interrogator, comprising:
providing an antenna having a coil that defines an area;
transmitting a pulse to said coil and receiving a response therefrom; and
estimating and subtracting a background signal level from said response from said coil and providing a residual therefrom, thereby discerning a presence of a metal object in said area.
12. The method as recited in claim 11 wherein said antenna is an antenna array and said coil is one of a plurality of overlapping coils of said antenna array.
13. The method as recited in claim 11 wherein said background signal level comprises a background metal object proximate said metal object.
14. The method as recited in claim 11 wherein said response is a decaying eddy current response.
15. The method as recited in claim 11 wherein said transmitting is performed by a transmit pulse generator.
16. The method as recited in claim 11 further comprising providing a sampled response and said estimating and subtracting comprises estimating and subtracting said background signal level from said sampled response.
17. The method as recited in claim 11 wherein said estimating and subtracting is performed by a control and processing subsystem comprising a multi-sample noise reduction subsystem, an intra-sample noise reduction subsystem and a detection subsystem.
18. The method as recited in claim 11 wherein said antenna is an antenna array having a plurality of coils and said estimating comprises averaging responses from said plurality of coils.
19. The method as recited in claim 11 wherein said subtracting comprises subtracting said background signal level point by point from said response.
20. The method as recited in claim 11 further comprising normalizing an integral value of said residual.