Design of a Circularly Polarized Ground Radiation Antenna for Biomedical Applications

A ground radiation antenna with circularly polarized (CP) properties is proposed and studied for biomedical applications. A square ground with a small clearance is implemented in the proposed antenna. Reactive components are included to realize the impedance matching, as well as those requirements for the generation of CP waves. Simulations are conducted within a single-layer tissue model to evaluate the antenna's performance. The proposed antenna exhibits a low profile, which is smaller than 1 mm even including two coating layers. The antenna also behaves good robustness to different implant depths and thicknesses of biocompatible coating, due to its wide axial ratio bandwidth ranging from 2.331 to 2.582 GHz. A prototype is fabricated and experimentally demonstrated in a solid skin-mimicking phantom. A measured impedance bandwidth of 621 MHz is achieved for the 2.4-2.48-GHz Industrial Scientific Medical band. Good agreement between simulation and measurement can be observed in the far-field measurement. The link budget is also evaluated, together with an exterior CP patch antenna.