Miniaturized Circularly Polarized Implantable Antenna for Leadless Pacemaker Devices

A circularly polarized implantable antenna working at 915 MHz industrial, scientific, and medical (ISM) band is presented. A meander line is used for miniaturization purposes, while a U-shaped structure is used not only to guarantee circular polarization performance but also to shift the band to lower frequencies. The designed antenna shows an impedance bandwidth of 20 % from 809.4 to 989.8 MHz and an axial ratio (AR) bandwidth of 27 % from 770 to 1010 MHz. The proposed antenna has a compact size of 5.2 mm x 5.6 mm. The proposed antenna achieves an acceptable gain value of -23 dBi. Furthermore, the geometry of the proposed antenna remains simple with a full ground plane and without using any via holes. Finally, the fabricated prototype has been experimentally tested inside minced pork, salmon fish, and beef meat, and the measured results show good agreement with the simulated one.