A passive implantable biopotential measurement sensor with an inductive coupled readout circuit

To measure biopotentials, a measurement method with a passive LC filtering is presented. The measuring system consists of two sections: an implantable sensor section and an inductive coupled readout circuit. The proposed sensor section consists of an inductor that receives power from outside of the body and a LC filter with which the received signal is filtered. This filter consists of an inductor that acts as a transmitter, too. So, the filtered signals could be sent outside of the body. The capacitive component of the LC filter is a varactor that its capacitance varies with the amplitude of the biopotential signal. This induces a change in the resonance frequency of the filter which can be measured over the inductive link. The overal system works like a spectrum analyzer.