Recent advances in electrical engineering have let the realization of small size electrical systems for in-body applications. Today’s hybrid implantable systems combine radio frequency and biosensor technologies. The biosensors are intended for wireless medical monitoring of the physiological parameters such as glucose, pressure, temperature etc. Enabling wireless communication with these biosensors is vital to allow continuous monitoring of the patients over a distance via radio frequency (RF) technology. Because the implantable antennas provide communication between the implanted device and the external environment, their efficient design is vital for overall system reliability. However, antenna design for implantable RF systems is a quite challenging problem due to antenna miniaturization, biocompatibility with the body’s physiology, high losses in the tissue, impedance matching, and low-power requirements. This dissertation presents design and measurement techniques of implantable antennas for medical wireless telemetry. A robust stochastic evolutionary optimization method, particle swarm optimization (PSO), is combined with an in-house finite-element boundary-integral (FE-BI) electromagnetic simulation code to design optimum implantable antennas using topology optimization. The antenna geometric parameters are optimized by PSO, and a fitness function is computed by FE-BI simulations to evaluate the performance of each candidate solution. For validating the robustness of the algorithm, in-vitro and in-vivo measurement techniques are also introduced. To illustrate this design methodology, two implantable antennas for wireless telemetry applications are considered. First, a small-size dual medical implant communications service (MICS) (402 MHz – 405 MHz) and industrial, scientific, and medical (ISM) (2.4 GHz – 2.48 GHz) band implantable antenna for human body is designed, followed by a dual band implantable antenna operating also in MICS and ISM bands for animal studies. In order to test the designed antennas in-vitro, materials mimicking the electrical properties of human and rat skins are developed. The optimized antennas are fabricated and measured in the materials. Moreover, the second antenna is in-vivo tested to observe the effects of the live tissue on the antenna performance. Simulation and measurement results regarding antenna parameters of the designed antennas such as return loss and radiation pattern are given and discussed in detail. The development details of the tissue-mimicking materials are also presented.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-3621 |
| Date | 11 December 2009 |
| Creators | Karacolak, Tutku |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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