Micro coils for improved power transfer in telemetry systems

To improve the transmission behaviour of a transponder system a new fabrication technique which enables the realisation of multiple layer micro coils by using single layer micro coils is presented. The single layer micro coils were realised by electroplating of 20 μm thick gold on a 9 μm thick polyimide film. Afterwards, the foil was folded together in such a way that the coils were adjusted one above the other. Using this technique double- and 4-layer coils with. different number of turns were fabricated. Compared to single layer coils the inductance of the coils increased by a factor of 3.3 for the double layer coils and by a factor of 12.4 for the 4-layer coils. In addition the obtained voltage drop across a 10 kΩ load resistance increased for both coil types (double and 4-layer coils) by more than 20% and across a 39 kΩ load resistance by more than 70%, respectively