  The fusion of metasurface antennas and computational imaging facilitates the
design of microwave imaging systems which require no lenses, phase shifters or
moving parts. The technique involves the generation of appropriately designed
diverse measurement modes to encode the scene information into a small number
of measurements. We propose a novel boundary-tunable parallel plate
waveguide-based metasurface antenna for computational microwave imaging. The
proposed antenna leverages a switchable boundary of two layers of vias, to
efficiently change the waveguide modes supported by the antenna cavity, leading
to diverse measurement modes in the scene plane. The superiority of the
boundary tuning approach over the frequency diversity approach for the same
antenna is confirmed using the singular value decomposition. Synthetic imaging
is performed using a coupled dipole model, which quantitatively proves the
efficacy of the proposed antenna along with the robustness against noise down
to 15 dB SNR.
