Patent ID: 7377445

Claim:
A radio frequency identification (RFID) transponder, comprising: an antenna to receive an interrogating RF signal and to receive a command for a state under a communication protocol, the communication protocol being a half duplex, reader talk first protocol; a memory to store data; a first circuit to demodulate the interrogating RF signal, the interrogating RF signal being amplitude modulated with a minimum of 90% modulation depth during a first portion of half duplex community; a second circuit to backscatter modulate the interrogating RF signal by changing a phase of the interrogating RF signal during a second portion of half duplex communication; logic to control the transponder in response to the command; and a state capacitor coupled to the logic and adapted to maintain the state despite a loss in power due to a lapse in receipt of the interrogating RF signal; wherein the state capacitor is adapted to maintain the state for at least 1 second despite the loss of power.