Abstract-For microwave imaging systems that utilize antennas with spatially separated feeds and apertures, arrival time correction based on the antenna aperture location is one of the fundamental steps in radar data processing. The estimates of the antenna aperture time and the corresponding average velocity in the material in contact with the antenna are expected to have a significant impact on the quality of the reconstructed image. In this paper, we propose antenna aperture and average velocity estimation by least-squares regression analysis of the first-breaks. The results indicate that the proposed method is able to process either the reflection data or the transmission data measured by antennas with different structures. Compared to those readily identifiable characteristics in the signal, the first-break is less influenced by waveform distortion and is able to provide more consistent reference. Differences in the images of test objects are also noted.

Abstract-In medical microwave imaging applications, electromagnetic (EM) waves propagate through human tissues, which are inherently attenuative and dispersive. In the resulting image, these effects translate to a lack of resolution that increases with time/distance. To produce microwave images with high resolution, there is a strong need for a technique that is able to compensate for the energy loss and correct for the wavelet distortion. Gabor nonstationary deconvolution was developed in the field of Seismology to compensate for attenuation loss, correct phase dispersion, and produce images with high resolution. In this study, the Gabor algorithm is proposed to deal with the nonstationarity in EM wave propagation and attenuation. Gabor deconvolution is essentially based on the assumption that the anelastic attenuation of seismic waves can be described by a constant Q theory. We investigate the Q characterization of EM wave propagation, the frequency-dependency of EM Q, and the effectiveness of Gabor deconvolution to deal with high loss and dispersion. To accommodate for the EM application conditions, several adjustments are made to the proposed algorithm. Our test results indicate that Gabor nonstationary deconvolution is able to sufficiently compensate for attenuation loss and correct phase dispersion for EM waves that propagate through lossy and dispersive media.

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