Patent ID: 8400274

Claim:
A method for counting Radio Frequency Identification (RFID) tags, comprising: sending no select commands to RFID tags in range of a reader for at least a known period of time for ensuring that all of the RFID tags in range of the reader are in an active state; interrogating each of the RFID tags in range of the reader; receiving a tag identifier from each RFID tag; instructing each tag to sleep upon receiving the tag identifier from the tag, wherein each tag remains in the sleep state for the known period of time, wherein the known period of time does not significantly vary regardless of whether the tag is powered or not, and generating a count of the tags, wherein the RFID tags each comprise a calibrated gate biasing circuit having a switched capacitor precision resistor and a voltage reference, wherein the voltage reference includes a matrix of forward biased diodes coupled to an outlet of the switched capacitor precision resistor.