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Presented in this letter is an improved version of the point scatterer vector tracking (PSVT) method for noise estimation in microwave coherent Doppler tomography (CDT). This new process of multipeak PSVT (MP-PSVT) significantly improves the quality of the tomogram given a noisy dataset. Phase shifts caused by positional displacements between the microwave source and center of rotation are compared against multiple isotropic scatterers placed within an image plane. Correlation between a subset of estimated shifts is then used to formulate a singular noise function. This noise function is used to deembed the original dataset thereby compensating for all phase errors. The example performed in this letter leads to a 0.91 correlation coefficient in the linear regression model containing the estimated noise and the applied noise. This new MP-PSVT approach significantly outperforms the original PSVT method. [ABSTRACT FROM AUTHOR]

This article demonstrates a new method of determining depth in wideband coherent Doppler tomography (CDT) using only a monostatic arrangement. The method was developed to eliminate the smearing effects present when imaging a target wrapped around a conformal surface. All that is required is the addition of isotropic targets placed around the subject under test (SUT). Using only a single data set, two images containing differing reference planes are generated. The new algorithm locates the position of these points and correlates the dispersion of the peak spectral power for each one. It has appropriately been named the dual-layer peak matching (DLPM) technique. The DLPM technique will be performed in both the measured and simulated environments to consolidate the robustness of the results generated. For both examples, positional error falls within the range resolution for the measurement setup. All steps are demonstrated from the data acquisition to the final result, allowing the user to predict the depth (from here on referred to as the “ $\boldsymbol {\Delta z}$ ” location) of multiple scatterers in space. Finally, a tomographic image will be generated that encompasses the DLPM technique to eliminate smearing in the measured example. [ABSTRACT FROM AUTHOR]

Ultra-wideband coherent Doppler tomography (UWB-CDT) is a method whereby complex frequency data are evaluated and back-projected at uniform angles around a subject under test (SUT). In the presence of phase shifts brought upon by the unwanted motion in the test equipment, generating a focused image becomes complex due to the nature of the back-projection integration process. This article will demonstrate a vector-based correction algorithm, which can be implemented during the nondestructive evaluation (NDE) of a target to compensate for down-range phase errors (brought upon by the factors external to the ideal measurement setup). This new method will be known as point scatterer vector tracking (PSVT). A coherent image can be constructed by using the returned scattering information contained within a complex time-domain envelope. For the proposed method, multiple vectors based on the estimated peak locations are used to track, correct, and reconstruct the path of an ideal point scatter. The demonstration of the algorithm with measured tomographic data combined with a simulated additive noise component is presented, along with a step-by-step approach to reconstruct the desired data set. It will be shown that by using this proposed method, a coherent CDT image with an average correlation coefficient of 0.71 can be recovered from the data that have been corrupted by the unwanted phase shifts. [ABSTRACT FROM AUTHOR]