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The primary impediment to analyzing two-dimensional transient scattering phenomena using classical marching-on-in-time-based integral equation solvers is these schemes' high computational complexity that scales as O (N s 2 N t 2 , where N s and N t denote the number of spatial and temporal degrees of freedom of the current on the scatterer. Here, three schemes that reduce this cost by permitting the rapid evaluation of the temporal convolution of a bandlimited transient source signature with the two-dimensional wave equation Green function are studied; these three methods rely on (i) blocked fast Fourier transforms, (ii) truncated singular value decompositions, and (iii) multiresolution concepts. The computational cost of all three proposed algorithms scales as O(N s 2 N t log α N t ) with α ≤ 2. The three schemes are compared on their respective multiplicative constants inherent in this cost estimate, their memory requirements, and their ease of implementation. [ABSTRACT FROM AUTHOR]

A novel cavity-backed slot antenna is designed for ground-penetrating radars. When attached to the ground surface, this antenna is capable of coupling electromagnetic power into the ground with the maximum efficiency over wide frequency bands. A simulation tool is developed to precisely model the interaction between the antenna and ground media. Three fabricated antenna prototypes exhibit at least 25% input impedance bandwidth over a range of ground materials. Furthermore, a two-element antenna array is built, and bi-static radar measurement reveals that the impact of air-ground interface is successfully removed when the array is placed conformal to the sand surface. [ABSTRACT FROM AUTHOR]