MICROWAVE IMAGING VIA SPACE-TIME BEAMFORMING FOR EARLY DETECTION OF BREAST CANCER: BEAMFORMER DESIGN IN THE FREQUENCY DOMAIN

Abstract

Microwave imaging via space-time beamforming has been proposed recently for early-stage breast cancer detection. In this paper we present an efficient frequency-domain approach to designing the beamformers. The low-power signal sequentially transmitted into the breast by each antenna in an array may be either an ultrawideband pulse or a sequence of sinusoidal signals with carrier frequencies corresponding to the discrete design frequencies. Backscattered waveforms collected at each transmitting antenna are processed in the frequency domain using beamformers designed to compensate for frequency-dependent propagation effects in normal breast tissue. Backscattered signal energy is computed and imaged as a function of location. We demonstrate the capability of this method to detect millimeter-sized tumors using representative backscattered waveforms computed from a two-dimensional anatomically realistic FDTD breast model. These simulation results show that localized regions of high energy levels in the images consistently correspond to small malignant tumors present in the breast.