Design of Small Circular Polarized Antenna With Ring Descriptive Loading for Biomedical Applications

A small circular polarized antenna for biomedical applications is designed, which can be used for signal transmission of implantable medical devices or capsule endoscopes. By introducing the ring characteristic loading array, the high electromagnetic energy is aggregated, and the electrical size of the antenna is reduced effectively while the impedance bandwidth is widened. Under the same bandwidth requirement, the antenna size is reduced by about 18 %, and the antenna volume is 80.7 mm(3). The circular polarization performance of the antenna is generated and adjusted by adding annular slots between the outer ring and the ring descriptive loaded array to generate geometric perturbations. The sensitivity of the complete antenna model to implant in different parts of human body and ingestion of different digestive organs is studied. The biological compatibility, radiation characteristics and safety of the antenna are evaluated. The gain values are -16.8 dBi and -15.6 dBi. The performances of the antenna are tested in pork and simulated digestive tissue solutions. The impedance bandwidths are 24.7 % (2.23 similar to 2.86 GHz) and 20.2 % (2.25 similar to 2.76 GHz) respectively, and the effective communication distance is 11.8m in space. The designed antenna has wide working frequency band, small size, anti-interference and good electromagnetic compatibility, which can meet the working requirements of biological medical equipment after ingestion in digestive organs or implantation in human body.