Analysis of Penetration Depth and Average SAR in Double-Ridge Open-Ended Waveguide Antennas for Skin Cancer Detection at Millimeter-Wave Regime

This paper presents the assessment of penetration depth and average specific absorption rate (SAR) in ultra-wideband double-ridge open-ended waveguide antennas (OE-WAs) for skin cancer detection at millimeter-wave (mm-wave) regime. Specifically, two double-ridge OEWAs with 15–40-GHz and 40–110-GHz bandwidths are designed and fabricated. Each antenna demonstrates |S
11
|<–10 dB and stable and symmetric radiation patterns across 15–40 GHz and 40–110 GHz with aperture sizes of 9.47×5.79 mm
²
and 3.78×2.27 mm
²
, respectively. To understand how the electric field affects the subcutaneous layers, a 3D realistic biological model consisting of skin, fat, and muscle is adopted. The findings suggest that the proposed antennas can detect early-stage skin cancer even in the worst-case situation of very thick skin, i.e., when cancer begins to grow at a depth of roughly 0.2mm, which corresponds to the bottom layer of epidermis. Additionally, the average SAR values are well within the Federal Communications Commission (FCC) safety standard.