Novel miniaturized antennas and arrays for implantable, ingestible and body-worn applications
- Publication Type:
- Thesis
- Issue Date:
- 2018
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Implantable medical devices (IMDs) introduced to monitor and transfer physiological information from inside the human body have superb potentials to provide major contributions to disease diagnosis, prevention and therapy. Moreover, minimally invasive biomedical devices helps to reduce the period of long-term hospitalization, so that enhancing the patients’ quality of life. Understanding and developing biotelemetry devices, recording/transmitting data from inside the body to the external base station, requires a multi-disciplinary approach. Such a challenging task merges applied solutions, concepts and models from various fields, including biology, electronics, electromagnetism and package/system engineering. Among the device components, the transmitter antenna plays a key role.
Antenna design for biotelemetry applications is extremely challenging due to the effect of the surroundings on the radiator, the essential requirement to miniaturize the antenna structure size, reduced antenna efficiency and the robust effect of multipath losses. More specifically, in this thesis, I design and fabricate several antennas to be integrated in ingestible and implantable devices useful for remote monitoring as well as data biotelemetry. This work also focuses on arrays of body-worn antennas for both wireless endoscope base stations and cancer treatment nearfield microwave systems. Here, my aim is to reduce the physical size of the implantable antennas at specified operating standards frequency bands, while maintaining the antenna electromagnetic performance satisfactory. To achieve this, I introduce and use valuable miniaturization techniques for implantable patch antennas for biotelemetry applications.
Additionally, I design and fabricate compact microwave systems for cancer treatment using electromagnetic (EM) energy. Non-Invasive Local Microwave Hyperthermia (NI-LMH), which is my interest in this thesis, is a heat treatment serves to enhance the effectiveness of chemotherapy or radiation therapy and leads to gain remarkable results. The system may directly apply heat to a fairly small specific area such as tumors to destroy the local cancer cells. To achieve this, the heat effect is developed in the target by the transmission of EM energy, using array of antennas, which is adjusted in frequency, time and strength in order to work together to form a focus in the target. This places high demands on the precision of the system.
In this thesis, I present different planar antenna array for non-invasive microwave hyperthermia applications. The new Near Field Focused (NFF) arrays operates at ISM 2.45 GHz band and consists of 5 to 25 miniaturized dual slot PIFAs, depends on the array geometry arrangement. The arrays immersed inside a coupling bolus occupies a very small volume of space results in an easy fitting to contoured patient anatomy. These arrays, which are low profile and lightweight, have both superficial and deep focusing properties. The novel NFF body worn arrays are capable to focus on a single target with a high level of accuracy to concentrate the EM energy only on the target. I employ optimized dual slot PIFAs as array elements to reduce the size of the focusing area so that destroying very small tumors and avoid heating up the surrounding healthy cells.
I have also introduced size reduced NFF array to simplify the feeding network of the applicator and reduce the system cost, this array configuration satisfies system requirements and can focus on small targets precisely while keep the penetration depth high enough to heat up the deep seated targets.
In addition, the performance of both fabricated narrowband and wideband single antennas and array of antennas verified using experimental tissue mimicking phantoms. To validate the dielectric properties of experimental phantoms, over different frequency bands, dielectric probe kit employed, furthermore, optical fibre thermometers employed to confirm specific absorption rate (SAR) values for implanted radiators.
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