An identification protocol that includes multiple identification
methodologies is used to isolate and identify a radio frequency (RF)
transponder. In accordance with a preferred embodiment of the present
invention, the RF transponder includes a memory device, an RF front end,
a random number generator (RNG), a counter, and a signal processing
circuit connected thereto and programmed to operate in accordance with an
identification protocol (or portions thereof). If multiple RF
transponders are transmitting their ID numbers simultaneously, the radio
frequency identification (RFID) base station may chose to resolve these
conflicts later by transmitting the {a} Next_Cycle command, which moves
the transponders back to a ready state. Alternatively, the {a} Fail
command can be used to isolate and identify individual RF transponders.
Once the transponder is isolated, it can be acknowledged and/or move to a
20 data_exchange state by transmitting a Read_New, FAK, PAK or AAK
command, each one having unique characteristics.