A miniaturized spiral antenna for energy harvesting of implantable medical devices

In this paper, a wireless power transfer system for implantable medical devices using a miniaturized 3 mm diameter single arm circular spiral antenna is presented. The transmission characteristics, S 21 between the transmitting and receiving antennas with air and tissue as a medium between antennas are analyzed and measured. The receiver antenna receives almost 2 mW average power with power transfer efficiency of 53%. The power transfer efficiency could still reach to 4% with 274 µW average received power, with placement of 1.5 cm tissue and 1 cm air in between two antennas. With one PN diode rectifier, the total DC power from the receiver side is 489 nW.