Microsystems for Wireless Sensor Networks with Biomedical Applications

Microsystems for Wireless Sensor Networks with Biomedical Applications

J. P. Carmo (University of Minho, Portugal), N. S. Dias (University of Minho, Portugal) and J. H. Correia (University of Minho, Portugal)
DOI: 10.4018/978-1-61520-670-4.ch002

Abstract

This chapter introduces the concept of wireless interface, followed by the discussion of the fundamental items, concerning the fabrication of microsystems comprising low-power devices. Using as example, a design of a RF transceiver the frequency of 2.4 GHz and fabricated using a UMC RF CMOS 0.18 µm process, it will be discussed the main issues in the design of RF transceivers for integration in wireless microsystems. Then, it will be presented two biomedical applications for wireless microsystems: the first is a wireless EEG acquisition system, where it is presented the concept of EEG electrode and the characterisation of iridium oxide electrodes. The other application, is a wireless electronic shirt to monitoring the cardio-respiratory function. The main goal of these applications, is to improve the medical diagnostics and therapy by using devices which reduces healthcare costs and facilitates the diagnostic while at the same time preserving the mobility and lifestyle of patients.
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1 Wireless Interfaces And Microsystems

1.1 Introduction

Wireless communication microsystems with high density of nodes and simple protocol are emerging for low-data-rate distributed sensor network applications such as those in home automation and industrial control. This type of wireless microsystem with sensors and electronics are becoming of interest for biomedical applications. Moreover, in order to implement an efficient power-consumption wireless sensor it is necessary to develop a low-power low-voltage RF CMOS transceiver. As is of common knowledge, the CMOS technology has reached its maturity. Therefore, design engineers used it for developing RF circuits. The advantages of CMOS technology are the higher integration, low-power consumption, low-voltage supply and low-cost compared with Bipolar technology. The use of CMOS process with low length for the channels of the MOSFETs is very important for high-frequency devices. As will be seen further in this chapter, this was one of the main reasons that were behind the choice of the UMC RF 0.18 μm CMOS process to design, optimise and fabricate, a radio-frequency (RF) transceiver for the operation in the frequency of 2.4 GHz.

Key Terms in this Chapter

RF Transceiver: Electronic system responsible to transmit and receive electrical signals in a reliable form;

Wireless EEG: EEG whose acquired signals are transmitted by radio frequency.

Biomedical Applications: Activities of science applied to the clinical medicine.

CMOS: Complementary metal oxide semiconductor.

Wireless Sensor Networks: A network comprising wireless nodes, whose principal function is to acquire physical measures and send them wirelessly towards a base station. Also, these nodes can work as relays to other nodes or directly to the base station, and it must possess the ability to temporarily store its acquired data and the data to be forwarded.

Microsystem: System comprising active and passive components of various technologies that were assembled in the same die, by a mounting process.

Cardio-Respiratory Function Monitoring: Monitoring of the breath rate at the same time, cardiovascular signals are being acquired.

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