Antennas for medical implants are being introduced continuously lately. Allowed to operate at 402–405MHz (Medical Implant Communication Services/MICS) they can be relatively large. Minimization of such antennas is not trivial and even when it is successful it can lead to very sensitive designs or with poor radiation characteristics. Further skin/air impedance causes efficiency issues and sets limits to maximum receiver/source distances. Added to that, Specific Absorption Rate (SAR) levels can be very high and maximum available power may be limited. In this work we will try to draw some basic conclusions about current designs and discuss limitations. To that end, several designs will be reviewed.
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