Optically frequency reconfigurable implantable antenna design for biotelemetry systems

Thanks to biotelemetry systems, early diagnosis and follow-up of various diseases can be made, the findings of physiological events such as blood sugar rate, pulse rate, body temperature, vascular pressure can be collected instantly and the patient's quality of life can be increased. The data obtained with the help of biotelemetry systems are transferred to the outside world through implantable microstrip antennas. This operation can be performed in frequency bands allocated by the FCC (Federal Communications Commission) such as MICS (402 − 405 MHz), MedRadio (401 − 406 MHz), ISM (433 − 435 MHz), ISM (902 − 928 MHz) and ISM (2.40 − 2.48 GHz). The radiation characteristics of the implant antennas, which perform in the surrounding tissue, change when the type of tissue they are placed in changes, leading to the inability to communicate. In this thesis, a compact structured implant antenna design suitable for use in biotelemetry applications, with a reconfigurable frequency, which can maintain the operating frequency band and change the operating frequency bands in the same tissue when the tissue type is changed by configuring the frequency by switching between the closed and open states of the used switching element, has been developed. The proposed antennas have square and circular geometry and both antennas are excited by coaxial feeding technique. In order to reduce the antenna size and keep the bandwidths at the best levels, split-ring (SR) and meander-line (ML) resonator structures were chosen as the main radiation elements. Convoluted structures contribute to miniaturization by increasing the length of the current paths on the resonator, while split-ring structures contribute to both improving the bandwidth and miniaturization due to intertwine. Frequency configuration feature is realized with a PIN-Photodiode added externally to the antenna. The photodiode is switched on with the help of an externally applied light and switching is performed. One of the designed antennas performs in three different tissues: skin, muscle and fat; The frequency can be adjusted by turning the photodiode to the closed position when the antenna is in the skin and muscle tissues, and on position when it is in the fat tissue. The other antenna designed performs only in muscle tissue, works in the ISM-2.4 GHz band when the photodiode is off, and works in the MICS, MedRadio, ISM-433 MHz, ISM-915 MHZ and ISM-2.4 GHz bands when it is on. Prototype production was carried out for the tests of the antenna, whose numerical design was carried out through CST Microwave Studio. The measurements of the produced antenna were carried out in a liquid phantom (In-vitro) showing the characteristics of human skin tissue at the relevant frequencies, in the pork minced meat supplied and in live pig (In-vivo) in accordance with ethical rules. When the return loss and radiation pattern characteristics of the antennas are compared according to the simulation and measurement results, it is observed that they are quite compatible. As a result, in this thesis study, considering the radiation characteristics, compact structure and reconfigurabilty of the originally developed frequency adjustable implant antennas in MICS and ISM bands used for biotelemetry applications, it is appropriate to use in these systems and by creating an output with a high impact factor in the literature, It is considered that it will shed light on the future studies.