Patent ID: 7791478

Claim:
An apparatus, comprising a radio frequency identification (RFID) device capable of processing a radio frequency (RE) signal modulated with a first frequency and a second frequency, the two frequencies representing two-bit combinations in any of these four combinations: a) the first frequency present and the second frequency absent; b) the first frequency absent and the second frequency present; c) the first and second frequencies both present; d) the first and second frequencies both absent; and wherein the RFID device comprises: a first down converter to convert the RF signal to an intermediate frequency (IF) signal that may be modulated with the first and second frequencies; a second down converter coupled to the first down converter to convert the IF signal to first base band signal in which the first frequency is represented by a particular frequency at a first output; a third down converter coupled to the first down converter to convert the IF signal to second base band signal in which the second frequency is represented by the particular frequency at a second output; a first filter coupled to the second down converter and a first detector coupled to the first filter, the first filter and the first detector to detect a presence of the particular frequency at the first output; a second filter coupled to the third down converter and a second detector coupled to the second filter, the second filter and the second detector to detect a presence of the particular frequency at the second output.