The Lippmann--Schwinger--Lanczos (LSL) algorithm has recently been shown to
provide an efficient tool for imaging and direct inversion of synthetic
aperture radar data in multi-scattering environments \cite{DrMoZa3}, where the
data set is limited to the monostatic, a.k.a. single input/single output (SISO)
measurements. The approach is based on constructing data-driven estimates of
internal fields via a reduced-order model (ROM) framework and then plugging
them into the Lippmann-Schwinger integral equation. However, the approximations
of the internal solutions may have more error due to missing the off diagonal
elements of the multiple input/multiple output (MIMO) matrix valued transfer
function. This, in turn, may result in multiple echoes in the image. Here we
present a ROM-based data completion algorithm to mitigate this problem. First,
we apply the LSL algorithm to the SISO data as in \cite{DrMoZa3} to obtain
approximate reconstructions as well as the estimate of internal field. Next, we
use these estimates to calculate a forward Lippmann-Schwinger integral to
populate the missing off-diagonal data (the lifting step). Finally, to update
the reconstructions, we solve the Lippmann-Schwinger equation using the
original SISO data, where the internal fields are constructed from the lifted
MIMO data. The steps of obtaining the approximate reconstructions and internal
fields and populating the missing MIMO data entries can be repeated for complex
models to improve the images even further. Efficiency of the proposed approach
is demonstrated on 2D and 2.5D numerical examples, where we see reconstructions
are improved substantially.
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Title
ROM inversion of monostatic data lifted to full MIMO