An Implantable Antenna With Broadside Radiation for a Brain–Machine Interface

The brain-machine interface (BMI) is a new area of research and it is still in the development stage. The key component for the brain-machine interface is internal and external antennas. In this paper, we propose an implantable antenna for wireless brain signal sensing and monitoring using an inhomogeneous multi-layer model of the human head. A model with seven layers composed of skin, bone, fat, dura, cerebro spinal fluid (CSF), grey matter, and white matter was adopted for our multi-layer model. The antenna was embedded below the bone and above the dura of the head phantom. Artificial tissue emulating (ATE) materials were fabricated in semi-solid form and measurement was carried out to check the permittivity and loss tangent of each semi-solid ATE. Implanted antennas for wireless brain signal monitoring data must be compact, lightweight, and biocompatible. The proposed antenna was designed with Taconic RF-35 as the substrate with an overall size of 10 mm x 10 mm x 0.5 mm
³
. The proposed antenna has a -10 dB reflection bandwidth of 2.42-2.50 GHz and a gain of -25 dBi at the broadside direction. The top and bottom insulators with a thickness of 0.5 mm each were also designed with a Taconic RF-35 substrate. A good agreement between simulated and measured results was achieved for the proposed antenna for both in free space and inside of head phantom.