Sofia Bakogianni

An Implantable Planar Dipole Antenna for Wireless MedRadio-Band Biotelemetry Devices

A novel implantable planar dipole antenna for operation in the Medical Device Radiocommunications Services band (401-406 MHz) is proposed. A basic skin-implantable antenna model is initially developed, and then a prototype is fabricated. The dipole antenna exhibits an extremely thin profile and a very small aperture size; antenna physical volume is approximately 18.1 mm 3. Effective size reduction is achieved by optimally canceling its inherent high capacitance through L-shaped reactive loading sections within the antenna structure. As demonstrated, the applied design methodology facilitates planar antenna miniaturization with adequate radiation response (gain, radiation pattern shape, and specific absorption rate). A liquid skin medium is employed to experimentally validate the antenna. Measured and simulated results are in good agreement.

Investigation of efficient wireless charging for deep implanted medical devices

A human tissue-implantable rectenna that is intended for wireless data telemetry and power transmission operation is considered. To that end, a compact-size planar inverted F-antenna (PIFA) that initially operates within the Medical Device Radiocommunications Service (MedRadio, 402-405 MHz) and the industrial, scientific and medical (ISM, 902.8-928 MHz) bands is considered in order to evaluate advantages and disadvantages of radiating versus inductive power harvesting at sub-GHz region. The inductive coupling is carried out in MHz region in order to employ very small (mm-diameter). The scenario considered focuses on implants embedded in depths higher than 10mm. The analysis is carried out inside the muscle tissue of a cylindrical three-layered phantom representing the human arm. The Specific Absorption Rate (SAR) performance of the implanted system is assessed. The RF-to-DC conversion efficiency is also taken into account.

Sub-1 GHz far-field powering of implantable medical devices: Design and safety considerations

Design and safety considerations for the development of wirelessly powered medical implants are discussed. Among others, we investigate the wireless transmission of adequate amount of power to the implanted device to ensure a reliable and long-term operation, and patient safety due to power absorption in biological tissues. Specifically, the power link performance between implantable and external dipole antennas in the sub-1GHz ISM (433.1-434.8, 868.0-868.6 and 902.8-928.0 MHz) frequency bands is evaluated in a generic level. Safety performance issues are, also, discussed. Finally, a radiofrequency energy harvesting system is developed with regard to the calculated wireless power link response.

On the Design of Miniature MedRadio Implantable Antennas

A design frame for developing miniature implant- able antennas at medical device radiocommunications band (401–406 MHz) is being sketched by addressing issues of resonance, efficiency, bandwidth (BW), and robustness. To that end, we visit fundamental design concepts of geometry, impedance matching, and quality factor Q and we show that a very small antenna insensitive to environmental variations and of optimum efficiency can be obtained. It is the first time, to our knowledge, that a Q calculation for miniature implanted antennas is conducted. In this paper, we consider a skin-tissue implantation scenario and planar dipoles with extremely thin profile and small aperture size. Notably, antennas’ physical volume does not exceed 25 mm3. Results indicate a strong dependence of resonance frequency on the antenna geometry for fixed physical size. In addition, external impedance matching proves to be inferior to integral matching via metallization in relation with antenna radiation performance (gain, efficiency, and quality of communication link). Finally, the quality factor Q of small fixed-size antennas highlights the influence of the design on the exhibited resonance and sensitivity response (impedance BW, tolerance to detuning, and gain stability). Simulations are accompanied by measurements with very good agreement underlying the importance of our approach.

Performance of an implantable printed folded dipole antenna for biomedical wireless communication

In this study, an implantable compact printed folded dipole antenna functioning in the Medical Implant Communication Service (MICS) frequency band (402 - 405 MHz) is proposed. The developed antenna, exhibiting dimensions of 19.6 * 2 * 0.254 mm3, is embedded into the skin and muscle tissues of a canonical head and trunk model, respectively. Antenna is easily tuned when implanted into the different phantoms. Resonance and radiation characteristics inside the tissue-simulating mediums are assessed and a communication link between the implanted antenna and an external module is established.

Temperature variations for adults and child human models inside elevator cabin

Electromagnetic absorption and temperature increase for adult man and woman as also as for a 5-year-old girl when they are using a mobile phone inside an elevator cabin are investigated. Numerically accurate models are utilized.

Fundamental design analysis of small implantable dipole antennas

Implantable devices for wireless biotelemetry applications in the Medical Implant Communication Service (MICS) band ask for miniature, low-profile, broadband and insensitive to environmental changes antennas. Fundamental design techniques, if applied properly, can lead to optimum results. In this work, we discuss the appropriate approach for designing extremely small planar dipole antennas. As demonstrated, modifications on antenna structure driven by current vector alignment and conductor coupling factors affect antenna effective dimensions. Also, metallization proves to offer greater antenna performance compared to impedance matching with lumped elements. Finally, the quality factor of two small dipole antennas is evaluated.