Telemetry for Biosensor Systems

Excerpt

This chapter will provide an overview of radio frequency (RF) telemetry systems by examining the design requirements of two contrasting systems: a wireless system designed to support Fast Scan Cyclic Voltammetry (FSCV) and a wireless system designed to support selective biosensors. Traditionally, RF design and analog circuit design were very complicated endeavors. Component interactions and non-ideal behaviors made such designs as much art as science. Today however, there are a wide variety of analog integrated circuits with near ideal behavior, and self-contained RF modules with built-in standardized protocols are available. In short, it is now very possible for a neuroscientist, with little or no knowledge of telemetry, to design and construct robust wireless acquisition systems.

In addition, there are a wide variety of commercial implants available for identification and physiological monitoring in animals. Currently available wireless implants can measure activity, core temperature, blood pressure, heart rate, blood flow, pH, biopotentials Electrocardiography (ECG), Electroencephalography (EEG), Electromyography (EMG) and respiratory rate [1]. Major suppliers include Data Sciences International (www.datasci.com), Biomedic Data Systems (www.bmds.com), and Respironics (www.minimitter.com). Most of these systems use some form of inductive power and telemetry, very low power transmitters or both. That is, these devices normally use proprietary low power analog transmitters that can only communicate over short distances, and in some cases the power required to operate the device is derived from RF energy transmitted from the receiver (Reader) to the device. A wide and impressive variety of Application Specific Integrated Circuits (ASIC) has also been developed. Mohensi et al. provide an excellent overview of current systems [2].

The goal of this chapter is simply to provide an overview based on familiar examples in the hope that this will help the reader to make informed decisions, whether building or buying telemetry based systems. To that end, we will consider the design of a digital wireless FSCV system for the measurement of electroactive species such as dopamine, and a biosensor based digital wireless system.