Design and Analysis of a Compact-Sized Multiband Spiral-Shaped Implantable Antenna for Scalp Implantable and Leadless Pacemaker Systems

In this communication, a multiband spiral-shaped implantable antenna for scalp implantation and leadless pacemaker systems is presented. The proposed antenna has the following operational bands: medical implanted communication service (MICS) (402-405 MHz), industrial, scientific, and medical (ISM) (433.1-434.8 MHz and 2400-2483.5 MHz), and midfield (1520-1693 MHz). The recommended antenna system consists of two implantable devices: a flat-type scalp implantable device and a capsule-type leadless pacemaker. In each device, the antenna is integrated with controlling electronic components and a battery. The proposed antenna has a compact size of 17.15 mm3 (7 mm x 6.5 mm x 0.377 mm). A significant size reduction for the antenna is achieved by using a spiral-shaped radiator with two symmetrical arms and introducing an open-end slot in the ground. The key features of the proposed antenna are its compact size, vialess ground plane, multibands, wide bandwidth, and satisfactory gain values compared to other implantable antennas. The maximum realized gain values of the proposed structure are -30.5, -30, -22.6, and -18.2 dBi at 402, 433, 1600, and 2450 MHz, respectively. The design and analysis of the antenna are carried out with simulators, based on the finite-element method (FEM) and the finite-difference time domain (FDTD). The performance of the antenna is experimentally validated using a saline solution and minced pork muscles. Moreover, the specific absorption rate (SAR) distributions at all frequencies induced by the implantable antenna are evaluated. In addition, a wireless communication link budget is calculated to specify the range for biotelemetry at data rates of 7 and 100 kb/s.