Controllable Wireless Power Delivery for Biomedical Implants

We demonstrate a method, independent of coil geometry, orientation and separation, to measure inductive wireless power transfer to an implanted coil, without a bidirectional communication link. Load switching on the implantable coil at 1 kHz modulates the 13.56 MHz carrier signal. A lock-in amplifier detects current perturbation in the excitation coil at the switching frequency producing an output proportional to the induced current in the implantable coil. Measurements show good agreement with analytical values at different locations in a 5mm x 5mm grid for parallel and orthogonal coil orientations. Observed standard deviations are within 10% and 15% for parallel and orthogonal orientations.