Abstract
The effect of using a superstrate dielectric layer on an on-head matched antenna for biomedical diagnosis applications is investigated. Two on-head matched antennas are considered with different length meandered lines ensuring operation around 0.9 GHz frequency. The first antenna’s conductive radiating structure is in direct contact with the head phantom, whereas the second one utilises a 0.5 mm thick superstrate layer on top of the conducting layer as a buffer. The lateral dimensions of both antennas are held constant at 30 × 30 mm2. The electric and magnetic field distribution is analysed and the power penetration, 50 mm inside the head phantom, is derived from the electromagnetic field surrounding the antennas. Both homogeneous and inhomogeneous head phantoms are considered while evaluating the antennas in terms of their reflection coefficient, current distribution, electric field, magnetic field, specific absorption rate (SAR) and power penetration inside the head. The antennas are fabricated and measured utilizing an inhomogeneous phantom to validate the proposed performance improvement using a superstrate. It is shown that the superstrate antenna achieves a ~8 dB increase in power penetration inside the head phantom along with a 0.0731 W/kg decrease in SAR compared to the antenna without a superstrate.
Highlights
The microwave regime has gained its popularity over the last decade for medical diagnosis applications due to its non-ionizing radiation, low-cost, and time efficient advantages
In this study we investigate the effectiveness of a superstrate layer on the performance of an on-head matched antenna, with regards to power penetration pattern and specific absorption rate (SAR)
Two antennas for on-head biomedical applications are designed with identical lateral dimension of 30 × 30 mm2, both operating at 0.9 GHz
Summary
The microwave regime has gained its popularity over the last decade for medical diagnosis applications due to its non-ionizing radiation, low-cost, and time efficient advantages. The top antenna conductor directly touches the human head surface to achieve impedance matching. Electronics 2020, 9, 1099 operation principle are reported in [10,11] for breast cancer detection application where the antenna conductor plane is in direct connection with the skin layer of the breast. Similar mechanisms to achieve antenna isolation from the human tissue are reported in [19,20,21] In all these proposed implantable antennas, a comparative characterization of the presence of a superstrate layer is omitted so the usefulness and impact of the superstrate cannot be determined. Inside a human head phantom are evaluated, considering both homogeneous and inhomogeneous lossy tissue models to establish the effect of a superstrate in antenna designs for biomedical applications
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