  We present the design, fabrication, and experimental characterization of a
two-dimensional, dynamically tuned, metasurface aperture, emphasizing its
potential performance in computational imaging applications. The dynamic
metasurface aperture (DMA) consists of an irregular, planar cavity that feeds a
multitude of tunable metamaterial elements, all fabricated in a compact,
multilayer printed circuit board process. The design considerations for the
metamaterial element as a tunable radiator, the associated biasing circuitry,
as well as cavity parameters are examined and discussed. A sensing matrix can
be constructed from the measured transmit patterns, the singular value spectrum
of which provides insight into the information capacity of the apertures. We
investigate the singular value spectra of the sensing matrix over a variety of
operating parameters, such as the number of metamaterial elements, number of
masks, and number of radiating elements. After optimizing over these key
parameters, we demonstrate computational microwave imaging of simple test
objects.
