Patent ID: 8653975

Claim:
A radio-frequency identification device comprising: a single antenna having an impedance and behaving as a dipole antenna when the radio-frequency identification device is in free space, and behaving as a balanced-feed microstrip antenna when the radio-frequency identification device is placed near a conductive surface, wherein the antenna has a power transfer efficiency of at least approximately 95% when the radio-frequency identification device is operating in free space and at least approximately 5% when the radio-frequency identification device is placed near the conductive surface; and an integrated circuit connected to the antenna and having a conjugate impedance, wherein the impedance of the antenna approximately matches the conjugate impedance of the integrated circuit when the radio-frequency device is operating in free space, and is within at least approximately 25% of the conjugate impedance of the integrated circuit when the radio-frequency identification device is placed near the conductive surface.