A Compact Circularly Polarized Antenna for Wireless Medical Applications

Abstract

In this article, a compact broadband circularly polarized implantable antenna is produced, operating at the 2.45 GHz Industrial, Scientific, and Medical (ISM) band for wireless medical applications. A multi‐layer tissue model is established as the simulation environment, where the antenna is placed at a depth of 3.5 mm beneath the skin surface, without any via holes. The antenna configuration is extremely compact, with a radiator size of only 4 × 4 mm, and the impedance bandwidth of 2.21–2.86 GHz (26.7%) is simulated. By cutting slots of different shapes to increase the current path, the miniaturization and circular polarization characteristics of the antenna are realized, and the 3 dB Axial Ratio bandwidth is 2.35–2.53 GHz (7.36%). The maximum value of the gain is −19.5 dBi at 2.45 GHz. To analyze the distance of wireless communication, the link budget is calculated at data rates of 7 Kbps, 100 Kbps, and 1 Mbps respectively. In addition, the specific absorption rate (SAR) is also calculated to ensure human safety. By setting the proposed antenna in pig skin, the measured impedance bandwidth is as wide as 15.1%, showing that the required ISM frequency band can still be covered.