A low-power ASK demodulator for inductively coupled implantable electronics

An amplitude shift keying (ASK) demodulator is presented which is suitable for implantable electronic devices that are powered through an inductive link. The demodulator has been tested with carrier frequencies in the range 1-15 MHz, covering most commonly used frequencies. Data rates up to several 100kbit/s are supported, suitable for complex implants such as stimulating electrode arrays or visual implants. The circuit is compatible with modulation depths in the range 10-100%. The low end of the range permits data transmission without significant reduction in power transfer, or the use of transmitter designs with limited modulation capability. The power consumption is 60 μW from a 3 V supply. The circuit has been implemented in a standard CMOS process.