A Flexible Circularly Polarized Millimeter-Wave Antenna for Breast Tumor Detection

This work reports the development and evaluation of a compact, flexible circularly polarized antenna intended for wearable breast tumor detection in the 30–40 GHz millimeter-wave band. The antenna occupies a physical size of 10 × 10 × 0.254 mm³ and is realized on a Rogers RT/Duroid 5880 substrate to achieve low dielectric loss and mechanical flexibility suitable for on-body use. The design provides an impedance bandwidth from 33.40 to 35.80 GHz and a 3-dB axial-ratio bandwidth of 34.20–35.90 GHz, centered at 34.75 GHz. A peak gain of 8.30 dBi and a radiation efficiency of approximately 90% are obtained, with antenna performance remaining stable under bending conditions. Tumor detection capability is investigated using S-parameter analysis on a multilayer hemispherical breast phantom, where variations in S-parameter caused by dielectric contrast indicate sensitivity to malignant tissue. In addition, specific absorption rate analysis confirms compliance with IEEE safety guidelines, with SAR values less than 1.6 W/kg. These findings show that the suggested antenna is appropriate for noninvasive millimeter-wave breast imaging intended for early cancer detection.