Automatic mode detection in a dual operating mode RFID tag
View Patent ↗A multi-mode, preferably dual mode, radio frequency identification (RFID) tag is adapted for automatic detection of whether a RFID reader located within communication range of the RFID tag is transmitting a continuous wave (CW) or modulated wave types of RF signal, and accordingly, mandating a response from the tag in read-only (RO) mode or read/write (R/W) mode, respectively. The tag includes means for designating one of the RO and R/W operating modes as a default mode of the tag, and for switching the tag from its default mode to its other operating mode, and vice versa, according to a rule for determining the frequency of occurrence of a selected event related to signal type of the reader. A device-implemented method of this automatic detection, and a method of fabricating the tag, are also disclosed.
1. A method for an RFID transponder to communicate with a first interrogator operating with a first interrogator communication protocol and with a second interrogator operating with a second interrogator communication protocol, wherein said first interrogator communication protocol is a read only protocol consisting of a read mode and wherein said second interrogator communication protocol is a read/write protocol consisting of a read mode and a write mode, wherein the transponder responds to one of said first and second interrogator communication protocols as a dominant protocol and the other of said protocols as interrogator communication a recessive protocol, said method comprising:
transmitting a first interrogation signal according to the interrogator communication protocol of the first interrogator or the second interrogator;
detecting said first interrogation signal by the transponder;
if the transponder detects said recessive protocol, switching automatically to said recessive protocol according to a reluctance rule based on the dominant protocol of the transponder and a first set of signal characteristics associated with said first interrogation signal detected by the transponder;
detecting a second interrogation signal by the transponder that is of a different protocol than said first interrogation signal;
if the transponder detects said dominant protocol, reverting automatically to the dominant protocol according to an acceptance rule based on the dominant protocol of the transponder and on a second set of signal characteristics associated with the second interrogation signal detected by the transponder;
wherein a first set of reluctance and acceptance rules for the first interrogator communication protocol and a second set of reluctance and acceptance rules for the second interrogator communication protocol are programmed into the transponder's hardware, the transponder responding according to said first set of reluctance and acceptance rules based on a programmed bit designating the first interrogator communication protocol as the dominant protocol or the transponder responding according to said second set of reluctance and acceptance rules based on said programmed bit designating the second interrogator communication protocol as the dominant protocol.
2. The method of claim 1 wherein said first acceptance rule is less stringent than said first reluctance rule and said second acceptance rule is less stringent than said second reluctance rule.
3. The method of claim 1 wherein said first and second sets of rules includes detecting a number of falling edges with a prescribed time of the detected signal.
4. The method of claim 3 wherein the first set of reluctance and acceptance rules includes detecting said number of falling edges of the detected signal within a first predetermined time period.
5. The method of claim 4 wherein the second set of reluctance and acceptance rules includes detecting said number of falling edges of the detected signal within second and third prescribed time period.
6. A method for an RFID transponder to communicate with a first interrogator operating with a first interrogator communication protocol and with a second interrogator operating with a second interrogator communication protocol, wherein said first interrogator communication protocol is a read only protocol consisting of a read mode and wherein said second interrogator communication protocol is a read/write protocol consisting of a read mode and a write mode, wherein the transponder responds to one of said first and second interrogator communication protocols as a dominant protocol and the other of said interrogator communication protocols as a recessive protocol, said method comprising:
transmitting a first interrogation signal according to the interrogator communication protocol of the first interrogator or the second interrogator;
detecting said first interrogation signal by the transponder;
if the transponder detects said recessive protocol, switching automatically to said recessive protocol according to a reluctance rule based on the dominant protocol of the transponder and a first set of signal characteristics associated with said first interrogation signal detected by the transponder;
detecting a second interrogation signal by the transponder that is of a different protocol than said first interrogation signal;
if the transponder detects said dominant protocol, reverting automatically to the dominant protocol according to an acceptance rule based on the dominant protocol of the transponder and on a second set of signal characteristics associated with the second interrogation signal detected by the transponder;
wherein a first set of reluctance and acceptance rules for the first interrogator communication protocol and a second set of reluctance and acceptance rules for the second interrogator communication protocol are programmed into the transponder's hardware, the transponder responding according to said first set of reluctance and acceptance rules based on a modifiable hardware status bit designating said first interrogator communication protocol as the dominant protocol or the transponder responding according to said second set of reluctance and acceptance rules based on said modifiable hardware status bit designating said second interrogator communication protocol as the dominant protocol.
7. The method of claim 6 wherein said first acceptance rule is less stringent than said first reluctance rule and said second acceptance rule is less stringent than said second reluctance rule.
8. The method of claim 6 wherein said first and second sets of rules includes detecting a number of falling edges with a prescribed time of the detected signal.
9. The method of claim 8 wherein the first set of reluctance and acceptance rules includes detecting said number of falling edges of the detected signal within a first predetermined time period.
10. The method of claim 9 wherein the second set of reluctance and acceptance rules includes detecting said number of falling edges of the detected signal within second and third prescribed time period.