RESUMO
Most measurement devices for bioimpedance spectroscopy are coupled to the measured object (tissue) via electrodes. At frequencies > 500 kHz, they suffer from artifacts due to stray capacitances between electrode leads as well as between the ground and object. The noninvasive measurement of the brain conductivity is hardly possible with surface electrodes. These disadvantages can be obviated by inductive coupling. The aim of this work was the development of a wideband transceiver for inductive impedance spectroscopy. In order to define its specifications, a feasibility study has been carried out with a simulation model for three different coil systems above a homogeneous conducting plate. According to simulation results, all systems render it possible to resolve conductivity changes down to 10(-3) (omega m)-1 at frequencies > 50 kHz. The transceiver electronics must then provide a resolution of > or = 1 microV and an excitation current of up to 1 A. The realized receiver matches these specifications with an S/N ratio of 22 dB at 1 microV in the frequency range of 50 kHz to 5 MHz.
