Window taper functions for subaperture processing. Page: 39 of 48
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2.6 Miscellaneous Comments
We now offer a number of comments concerning various aspects of subaperture
processing.
" The biggest issue with employing subapertures is that the output spectrum
generally exhibits undesirable grating lobes. These grating lobes are in fact
aliased mainlobe due to the decimation of the data rate inherent in the subaperture
offsets.
" The fine-resolution window taper function determines near-in sidelobe response,
whereas the coarse-resolution window taper function generally determines the
nature of the grating lobes insofar as how fast they fall off in amplitude with
distance from the mainlobe. The offset and overlap of the subapertures
determines the spacing of the grating lobes.
" In some circumstances, the proper choice of coarse-resolution window taper
function can substantially reduce the amplitude of the grating lobes by placing the
grating lobes into deep nulls with sufficient null-width. This is especially true for
the special case where the subapertures are processed to the final output bin
spacing.
" There is an inherent worsening of achievable resolution in the output spectrum by
a factor N/(M2A2). This is usually small, but very real. It can be compensated
by collecting a longer input data vector with this in mind.
" Not explored herein, but nevertheless not out of the question, is the possibility of
using different subaperture window taper functions for different subapertures. In
fact, no explicit requirement exists to even maintain the same subaperture size, or
a constant subaperture offset.
" The concept of subapertures was explored herein in the context of evaluating a
signal's frequency spectrum. These concepts are quite applicable to multi-phase-
center antennas as are commonly employed in high-performance Interferometric
radar systems. Furthermore, the concepts herein can be extended to multi-
dimensional apertures, including applications in image processing and in antenna
systems.- 39 -
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Doerry, Armin Walter. Window taper functions for subaperture processing., report, December 1, 2013; Albuquerque, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc869303/m1/39/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.