A 2-to-16GHz 204mW 3mm-resolution stepped-frequency radar for breast-cancer diagnostic imaging in 65nm CMOS

Radar imaging is gaining interest for medical, security, and industrial applications. Enabled by the advances in silicon technologies, a clear trend towards higher integration is observed [1-3]. Early-stage breast cancer detection is a promising application for radar imaging, as first clinical trials with patients have been carried out [4]. Commercial VNAs have been used in these experiments, but custom hardware is needed to improve the sensitivity, and to decrease the size and the cost of the setup [4]. Medical radar imaging sets great challenges. The radiation must be coupled into the body, while the skin acts as a shield. The waves that penetrate beyond the skin are heavily attenuated (>80dB for a few centimeters at 10GHz [4]). Tumor cells have different electrical properties than the healthy tissue, thus reflecting the waves and allowing for detection; this contrast is frequency dependent, decreasing at higher frequencies. These fundamental limits result in a radar requiring a dynamic range in excess to 100dB [4], and force operation in the lower-GHz range. In contrast, mm-Waves would be preferred to achieve higher resolution [1]. Ultra-wideband radars combine larger scattered energy collected at lower frequencies (thus higher SNR), and mm-range resolution, since the resolution is set by the overall bandwidth and the antenna array arrangement [2].