A Wideband Circular Polarization Implantable Antenna for Health Monitor Microsystem

A compact implantable antenna is proposed for wireless health monitor microsystem, which is operated in frequency of the Industrial, Scientific, and Medical (ISM) band. A circular radiator is cut four L-shaped slots and loading a shortpin between the radiator and ground plane to implement the circular polarization. Two crossed rectangle slots are etched on the ground plane so that the impedance and axial ratio (AR) bandwidths have been expanded at the same time. In addition, to further verify the performance of the antenna for biomedical application, we simulate a microsystem that monitors human health; and establish the simulation environment of the human heart and head. Then, we evaluated the performance of the microsystem in the human tissue simulation environment. The maximum specific absorption rate value satisfies the IEEE standard safety guidelines. The experiment results indicate that the impedance and AR bandwidths of proposed antenna are 2.25–2.78 GHz and 2.32–2.63 GHz, respectively. The total dimensions of π × 4
²
 × 1.27 mm
³
are obtained, which is equivalent to π × 0.032
λ
₀
²
 × 0.0102
λ
₀
(
λ
₀
is the free-space wavelength at 2.4 GHz). This compact size is very suitable for the application in health monitoring microsystem.