A Circularly Polarized Omnidirectional Antenna for Wireless Capsule Endoscope System

This article presents the first report of a circularly polarized (CP) omnidirectional radiation antenna for wireless capsule endoscope (WCE) system applications. The proposed antenna incorporates an integrated design concept, and achieves operation at 0.915 GHz Industrial, Scientific, and Medical (ISM) band (0.902–0.928 GHz) with a compact size of
$\pi \times 5.5^{2} \times 22 \text {mm}^{3}$
. The simulation is performed in Ansys HFSS, with the antenna being placed in the center of a cylindrical homogeneous muscle tissue with a size of
$\pi \times 55^{2} \times 80\,\,\text {mm}^{3}$
. The simulated results show that the capsule antenna has an impedance bandwidth (BW) (
$\vert S_{11} \vert < -10$
dB) from 0.82 to 0.99 GHz and a CP BW (AR < 3 dB) from 0.84 to 1.09 GHz. Moreover, the omnidirectional CP radiation properties remain stable for a very wide
$\theta $
range (49°–144°) in the elevation plane. The robust CP performance and the integrated design concept make the proposed antenna suitable for advanced WCE systems.