Measurement of Wireless Link for Brain–Machine Interface Systems Using Human-Head Equivalent Liquid

In this letter, we analyze the wireless power transfer from an on-body transmit antenna to a millimeter-size antenna in a cortical implant. The studied wireless link provides power and data telemetry for a battery-free wireless brain-machine interface microelectronic system. We present a cubic 2 × 2 × 2 mm3 implant loop and analyze the effect of a magneto-dielectric core material on the performance of the antenna. We compare the wireless link performances to two different transmit antennas: solid and 2-segmented loops. Our simulation results show that the 2-segmented loop provides reduced near electric field, but maintains the link power efficiency. Finally, we validate the simulated link power efficiencies through measurements in air and in human-head equivalent liquid at 300 MHz.