Detection and classification of vulnerable road users (VRUs) such as pedestrians and cyclists is a key requirement for the realization of fully autonomous vehicles. Radar-based classification of VRUs can be achieved by exploiting differences in the micro-Doppler signatures associated with VRUs. Specifically, machine learning (ML) algorithms can be trained to classify VRUs using the spectral content of radar signals. The performance of these models depends on the quality and quantity of the data used during the training process. Currently, data collection is typically done through measurements or low fidelity physics, primitive-based simulations. The feasibility of carrying out measurements to collect training data is typically limited by the vast amounts of data required and practicality issues when using VRUs like animals. In this paper, we present a computationally efficient, high fidelity physics-based simulation workflow that can be used to obtain a large quantity of spectrograms from the micro-Doppler signatures of VRUs. The simulations are conducted on full-scale VRU models with a 77 GHz, frequency-modulated continuouswave (FMCW) radar sensor model. Here, we collect the spectrograms of 4 targets; car, pedestrian, cyclist and dog at different speeds and angles-of-arrival. This data is then used to train a 5-layer convolutional neural network (CNN) that achieves nearly 100% classification accuracy after 5 epochs. Studies are conducted to investigate the impact of training data size, velocity and observation time window size on the accuracy of the CNN. Results from this study demonstrate how an accuracy of 95% can be realized using spectrograms obtained over a 0.2 s time window.

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Experimental and theoretical approaches to verify the\ud validity of the incremental theory of diffraction (ITD) are considered.\ud After providing a simple recipe for the application of the ITD,\ud three geometries are examined for its validation. First, the ITD formulation\ud of the diffraction from a perfect electric conductor (PEC)\ud straight wedge is compared with the uniform theory of diffraction\ud (UTD) and with measurement results. Second, the ITD formulation\ud of the diffraction from a PEC disc is compared with measurement\ud results and with the exact solution of a boundary value problem\ud involving oblate spheroidal functions. Third, the ITD formulation\ud of the diffraction from a hole in a PEC plane is compared with the\ud exact solution of a boundary value problem involving oblate spheroidal\ud functions. In particular, this is the first time that ITD results\ud for diffraction from the disc and hole in a plane geometries are\ud validated using exact solutions computed at a caustic. In all cases\ud examined, very good agreement is found

An Incremental Fringe Formulation (IFF) for the scattering by large metallic objects illuminated by electromagnetic Complex Source Points (CSPs) is presented. This formulation has two main advantages. First, it improves the accuracy of Physical Optics (PO) computations by removing spurious scattered field contributions and, at the same time, substituting them with more accurate Incremental Theory of Diffraction field contributions. Second, it reduces the complexity of PO computations because it is applicable to arbitrary illuminating fields represented in terms of a CSP beam expansion. The advantage of using CSPs is mainly due to their beam-like properties: truncation of negligible beams lowers the computational burden in the determination of the solution. Explicit dyadic expressions of incremental fringe coefficients are derived for wedgeshaped configurations. Comparisons between the proposed method, PO and the Method of Moments (MoM) are provided.

[1] A semielliptical channel flush-mounted under a metal plane and slotted along the interfocal distance of its cross section is separated from the half-space above by a multilayer diaphragm. The cavity, the diaphragm, and the half-space are all isorefractive to each other. Both the cavity and the multilayer diaphragm are filled with materials isorefractive to the medium in the half-space above. This is a two-dimensional geometry where the source is invariant with respect to the axial variable. The resulting electromagnetic boundary-value problem is solved exactly in terms of Mathieu functions, when the excitation source is either a plane wave or a line source. For plane wave incidence, the polarization is with either the electric or the magnetic field parallel to the axis of the structure and the direction of incidence is arbitrary in a plane perpendicular to the axis. For line source excitation, the polarization is with either the electric or the magnetic field parallel to the axis of the structure and the source is arbitrarily located. Numerical results are also provided.Citation: Canta, S. M., and D. Erricolo (2008), Exact 2-D scattering from a slot in a ground plane backed by a semielliptical cavity and covered with a multilayer isorefractive diaphragm, Radio Sci., 43, RS6006,