Fully Integrated Miniaturized Wireless Power Transfer Rectenna for Medical Applications Tested inside Biological Tissues

This work presents the results of the characterization of two 1 x 5 mm2 miniaturized rectennas developed for medical applications. They have been designed for relatively high voltage and high-power applications, given the size of the rectennas. Both rectennas were tested in open-air conditions and surrounded by pork fat and muscle tissues, whose properties are similar to those of the human body. The resonant frequencies of the rectennas were found, and the incident electric field on the rectennas tests was increased. The first chip showed a maximum output voltage of 5.29 V and a maximum output power of 0.056 mW, at 1.446 GHz, under an incident field on the rectenna of 340 V/m, and the second chip, 4.62 V and 4.27 mW, at 1.175 GHz, under 535 V/m. The second rectenna can provide an output power greater than 5 mW. The rectennas presented in this article are beyond the state of the art, as they can deliver about three times more power and voltage than those of similar dimensions reported in the literature. Based on the test results, the efficiency of the rectennas was analyzed at different locations of the human body, considering different thicknesses of tissues with high and low water content. Finally, potential applications are described in which the rectennas could power implantable medical devices or microsurgery tools, for example, pulmonary artery pressure monitors.