6 research outputs found
Limits of WPT through the human body using Radio Frequency
Recently, the medical community has been devel oping new technologies to enhance medical treatments and diagnosis means, having in mind the patients’ comfort and safety. Implantable medical devices are an example of such solutions. Nonetheless, these devices present some disadvantages, namely need of batteries. Hence, these implants have a limited lifetime, and require periodical surgical interventions to change or to recharge. In order to solve this problem, systems based on Radio Frequency (RF) has been developed to transfer energy inside the organism. However, transmitting power to inside the human body must be performed carefully, since high power levels might be prejudicial to the subject. In this context, the goal of this work is to study the performance of the Wireless Power Transfer (WPT) to inside the human body, while respecting the Specific Absorption Rate (SAR) limits. Therefore, the levels of absorbed power in different body parts were verified by simulation, in order to reach conclusions about the user’s safety. More specifically, two biological models that represent the thigh and the arm were considered. The simulation results led us to conclude that it is possible to transmit approximately 140 mW on the limbs location, while respecting the SAR limits. In turn, it is possible to receive a power superior to 93 µW inside the human body. Additionally, real tests were also carried out in three subjects to verify the power attenuation related to each body structure.info:eu-repo/semantics/publishedVersio
Specific Absorption Rate-Aware Beamforming in MISO Downlink SWIPT Systems
This paper investigates the optimal transmit beamforming design of
simultaneous wireless information and power transfer (SWIPT) in the multiuser
multiple-input-single-output (MISO) downlink with specific absorption rate
(SAR) constraints. We consider the power splitting technique for SWIPT, where
each receiver divides the received signal into two parts: one for information
decoding and the other for energy harvesting with a practical non-linear
rectification model. The problem of interest is to maximize as much as possible
the received signal-to-interference-plus-noise ratio (SINR) and the energy
harvested for all receivers, while satisfying the transmit power and the SAR
constraints by optimizing the transmit beamforming at the transmitter and the
power splitting ratios at different receivers. The optimal beamforming and
power splitting solutions are obtained with the aid of semidefinite programming
and bisection search. Low-complexity fixed beamforming and hybrid beamforming
techniques are also studied. Furthermore, we study the effect of imperfect
channel information and radiation matrices, and design robust beamforming to
guarantee the worst-case performance. Simulation results demonstrate that our
proposed algorithms can effectively deal with the radio exposure constraints
and significantly outperform the conventional transmission scheme with power
backoff.Comment: to appear in TCO