Title

Low-power CMOS receiver for medical implant communication services

Date of Award

2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical Engineering and Computer Science

Advisor(s)

Numan S. Dogan

Second Advisor

Ercument Arvas

Keywords

CMOS, Medical implant communication services, MICS, Ultralow-power receivers

Subject Categories

Biomedical | Electrical and Computer Engineering | Engineering

Abstract

The emerging technology in the field of wireless sensor networks has brought many opportunities as well as many challenges to the design of radio links. Recently, the demand for low-cost ultra-low-power wireless transceivers with CMOS technology has increased significantly. These circuits are now utilized in numerous applications ranging from medical systems and home electronics to space applications and environmental systems. Among these applications, medical implant devices especially require ultra-low-power circuitry due to limited size and capacity of the batteries implanted in the human body.

This thesis does not only demonstrate the design and the implementation of an ultra-low-power fully-integrated UHF MICS (Medical Implant Communication Service) receiver in a 0.18 μm RF CMOS technology, but it also identifies the problems and challenges of designing sub-mW UHF receiver blocks under reduced supply voltage.

In order to mitigate the image rejection problem in low-IF architectures, the study has adopted a direct-conversion receiver architecture which is suitable for an ultra-low-power implementation. Furthermore, the design issues associated with low-voltage receiver blocks such as single-ended LNA, differential LNA, active mixer, pre-amplifier, tunable continuous-time low-pass filter and limiting amplifier are also discussed in details.

In this thesis, the receiver designed for medical implant communication service is equipped with an FSK demodulation scheme and tunable bandwidth suitable for different types of implant applications. The overall gain of this receiver is close to 150 dB which is high enough to clip the signal at the output. All of the circuits in this study have been designed to operate with 1 V reduced supply voltage. The power dissipation of the entire receiver is around 4 mW. After proper de-embedding of the parasitic effects introduced by the measurement instruments and the testboard, a good match between the simulated and the measured responses is observed. This successful match proves the robustness of the design and the viability of fully-integrated ultra-low-power medical implant receivers operating under the reduced supply voltage.

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