A medical implant comprising a housing and an antenna member carried by
the housing. The antenna member is configured to be capacitively coupled
to body tissue in which the housing is implanted. This forms, together
with the impedance of the body tissue, part of a resonant circuit. A
reference electrode carried by the housing as a return for the antenna
member also forms a further part of the resonant circuit. Transceiver
circuitry is also provided and is operable as at least one of a source
and a load for the antenna member and forms yet a further part of the
series resonant circuit.