Low Power Frequency-Shift Keying Demodulators for Biomedical Implants

This Low power frequency-shift keying (FSK) demodulators are presented for the biomedical implants. Two FSK demodulators are designed with different concepts. The analog FSK (A-FSK) demodulator is composed of a single balance mixer, a square wave generator, a charge pump circuit, and a comparator to achieve the demodulation. The other digital FSK (D-FSK) demodulator employs only one block which the output signals for stimulating can be obtained simply and directly. Both demodulators are implemented by tsmc 1P6M CMOS process at IV supply voltage. A-FSK demodulator occupies chip area of 0.016 mm² . The data rate is 2.5Mbps while receiving 2.5MHz/5MHz FSK carrier signals. While receiving 5MHz/10MHz FSK carrier signals, the data rate of the D-FSK demodulator is up to be 5Mbps. The D-FSK demodulator occupies 0.004mm². The power consumption of the A-FSK and D-FSK demodulators are 0.47mW and 0.022mW, respectively.

I. Introduction

With the rapid development of the biomedical systems recently, many researchers are interested in designing the implantable bioelectronics devices such as cochlear implant, retinal prostheses, and muscular stimulation. Among the implantable bioelectronics devices, the demodulator block plays an important role to retrieve a serial bit stream along with a reference clock. Because of the implantationg consideration, all systems have external parts and internal parts in order to delivery the desired signals. The signals are designed to be modulated in the external parts.