Time-Domain Wideband Adaptive Beamforming for Radar Breast Imaging

A novel wideband microwave radar imaging method is presented to detect regions of significant dielectric contrast within the breast. Clutter reduction is paramount to any radar imaging algorithm, especially with clinical patient data where the tissue composition of the breast is inhomogeneous. Time-domain data-adaptive imaging methods have been previously applied in a narrowband manner for microwave radar breast imaging when the received signal spectral content was wideband. In this study, a wideband time-domain adaptive imaging approach is presented to perform data-adaptive focusing across the spectrum to reduce clutter. An equalization filter is adapted to compensate for the propagation distortion through tissue using a calculated estimate of the average dielectric properties of the breast. The effectiveness of the proposed wideband adaptive imaging approach is evaluated in conjunction with the delay-and-sum (DAS) method using numerical, experimental, and clinical data. Target scatterers are clearly detected while clutter levels are reduced significantly, between 4 and 6 dB, when compared to the DAS technique.