Patent ID: 7692546

Claim:
An antenna for a backscatter-based RFID transponder comprising: an integrated receiving circuit having a capacitive input impedance for receiving a radio signal lying spectrally within an operating frequency range; and two antenna arms that extend outwardly in a spiral from a central area in which the antenna arms are connected to the integrated receiving circuit, wherein said antenna arms together exhibit a plurality of resonance frequencies including a first plurality of series resonance frequencies when a reactance of said antenna arms passes from a capacitive reactance to an inductive reactance and a second plurality of parallel resonance frequencies when said reactance passes from an inductive reactance to a capacitive reactance, wherein each antenna arm has an arm length along the arm, which is selected so that one of the series resonance frequencies of the antenna is below the operating frequency range and the next higher parallel resonance frequency of the antenna is above the operating frequency range.