Design of an Ultra-Wide Bandwidth Circularly Polarized Implantable Antenna for Wireless Biological Telemetry Systems

This paper presents an ultra-wide bandwidth circularly polarized implantable antenna for wireless biological telemetry systems. The effective axial ratio bandwidth of this antenna covers the 2.4 GHz industrial, scientific, and medical frequency band and the 1.9 GHz mid-field band. Its size is 0.028λ₀×0.057λ₀×0.004λ₀ (whereλ₀ represents the wavelength of the lowest operating frequency in free space). Miniaturization is achieved by adding rectangular slots to the radiation patch to form a symmetrical rectangular meandering structure, and introducing shorting probes. By etching an orthogonal rectangular slot on the ground plane and optimizing the position of the shorting probes, this antenna ultimately obtained effective axial ratio bandwidths of 0.31 GHz at 1.9 GHz and 0.53 GHz at 2.45 GHz, along with gains of −27.3 dBi at 1.9 GHz and −23.1 dBi at 2.45 GHz. The simulation verified the specific absorption rate and link margin, and the designed antenna conformed to the IEEE safety standard (IEEE C95.1-1999) and the requirements for reliable communication. Finally, the influence of the antenna integrated in the implantable device is tested in the skin, arms, head, and minced pork. The study confirmed that this antenna can maintain stable performance at different implantation environments.