A new discriminator for a low-power capacitor-less FSK demodulator for biomedical implants

Abstract

Many implantable micro-stimulator systems have been proposed in recent years. Communications between the implanted device and outside world is done through an inductive link, which is also used for delivering to the circuit the power required for its operation. Reducing the power consumption and chip area are the key issues in this field. This paper presents a new low power C-less (no capacitor) FSK demodulator which can be used in implantable biomedical devices. The demodulator circuit derives the serial data output and a constant frequency clock from the input FSK carrier. Demodulation procedure is based on the pulse-shrinking principle, in which the pulse width shrinks in successive stages. The circuit is designed and simulated using a commercial 0.18µm CMOS technology. The power consumption of the designed circuit is 42µw from a 1.8 volt power supply with a bit rate of 5Mbps.