Abstract
Biomedical implantable devices have appeared for more than fifty years. With more understandings of neuroscience, some diseases caused by neural abnormal discharge or disable may be cured or improved by neural stimulation techniques. Most of the wireless implantable devices transmit power and data into the no-battery implantable device by magnetic coupling. And the bidirectional data transmission, we can control and monitor the implantable system. This thesis presents the wireless power and bidirectional data transmission for biomedical implantable SoC. The chip contains power regulator, ASK (Amplitude Shift Keying) demodulator and FSK (Frequency Shift Keying) modulator, using the TSMC 0.18μm CMOS processing. The chip size is 0.031mm^2.(Without PAD) The transmission system utilizes coils electric magnetic field coupling the power and data into the chip, Power regulator produces the stability power for chip and other circuits. The ASK demodulator can decode the ASK signal and provide the clock signal. The FSK modulator can encode the implantable device data signal which wanted to transmit out, and transmitted through coil coupling. This study presents a novel ASK demodulator using the self-sampling structure for biomedical implantable devices. The modulation index and modulation rate are relative to power transmission efficiency. Results show that with a 2MHz carrier, the proposed ASK demodulator structure has a minimum modulation index down to 4.05% and a 50 % maximum modulation rate. The ASK demodulator also has a controllable modulation index and maintains a constant high-efficiency modulation rate for biomedical implantable systems.