AEL are involved in the development of time/ frequency algorithms for 2 and 3 dimensional radar imaging based on the construction of a synthetic aperture. These algorithms are all wave based in that the aperture is built by first decomposing the field into the wave components and then propagating the components to the observer where they are coherently combined to generate an image. Such wave based computations are well matched to the computational physics approach adopted throughout the company.
A key feature of AEL's involvements has been the development of imaging algorithms for time domain fast transient signals. These signals have no carrier frequency and hence the concept of Doppler shift, which is widely used in conventional SAR processing, is no longer relevant. However the wave based decomposition/propagation technique can be used for arbitrary bandwidth signals and hence transient imaging in 2 and 3 dimensions carried out.
As an example we show a 2-D image of 4 closely spaced dielectric cylinders. The return signal from such non-metallic objects is usually very small but with a transient imager the targets appear much brighter due to an internal wave focussing effect. In effect over a short sub-nanosecond time period the cylinders are acting as a "cats-eyes" reflector to the radar pulse.
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