Miniaturized High Gain Flexible Spiral Antenna Tested in Human-Like Tissues

A miniaturized helical antenna is presented in this work. The antenna is flexible, it is 6100 μm long and it has a diameter of 352 μm. This antenna has such a small cross-section, that permits to be implanted in the human body with fine syringes and minimally invasive surgeries. The antenna can be used to receive power and/or send information in medical devices. The antenna is made of biocompatible materials: polytetrafluoroethylene (PFTE) and copper. The fundamental parameters of the antenna have been simulated and experimentally measured in animal human-like tissues, showing good agreement. The resonant frequency of the antenna is 4.7 GHz, with a reflection coefficient of −25.1 dB, and a gain of −4.7 dBi. As expected, the resonant frequency decreases inside biological tissues comparing to the free-space open-air measurement. Reducing the resonant frequency is an advantage because power signals can penetrate deeper into body tissues.