Interferometric aperture synthesis for next generation passive millimetre wave imagers

Salmon, NA, Wilkinson, P and Taylor, C (2012) Interferometric aperture synthesis for next generation passive millimetre wave imagers. [Conference or Workshop Item]

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Abstract

This paper discusses the phase effects in the near-field associated with aperture synthesis imaging. The results explain why in some regions of the near-field it is possible to use Fourier transform techniques on a visibility function to create images. However, to generate images deep inside the near-field alternative processing techniques such as the G-matrix method are required. Algorithms based on this technique are used to process imagery from a proof of concept 22 GHz aperture synthesis imager [1]. Techniques for generating synthetic cross-correlations for the aperture synthesis technique are introduced and these are then validated using the image creation algorithms and real data from the proof of concept imager. Using these data the phenomenon of aliasing is explored. The simulation code is then used to illustrate how the effects of aliasing may be minimised by randomising the locations of the antennas over the aperture. The simulation tool is used to show how in the near field the technique can provide a range resolution in 3D imaging of a couple of millimetres when operating with a wavelength of 13 mm. Moving to illustrate the quality of images generated by a next generation aperture synthesis imagers, the software is extended to systems with hundreds of receiver channels