Phaseless coherent and incoherent microwave ghost imaging with dynamic metasurface apertures

Phase information and spatially coherent illumination have usually been considered indispensable components of most microwave imaging systems. Dynamic metasurface apertures (DMAs)—with their ability to generate spatially incoherent illumination—have recently supplanted these assumptions in favor of simplified imaging hardware. In light of this development, we investigate the coherence of a phaseless imaging system based on metasurface apertures. In doing so, we propose and experimentally demonstrate coherent and incoherent computational microwave ghost imaging using DMAs. These apertures can generate a multitude of distinct speckle fields at a single frequency by modulating the electrical properties of radiating complementary metamaterial elements patterned into the surface of a waveguide. We show that a pair of dynamic apertures, one acting as transmit and the other as receive, can achieve two-dimensional, phaseless, coherent imaging. Further, by averaging the intensity measurements obtained in this manner over a random set or ensemble of receive aperture distributions, we demonstrate that an incoherent imaging system can be achieved in which single-port ensemble averaging by the electrically large DMA plays the role of spatial averaging in a bucket detector. We investigate the effects of these different imaging schemes on the resulting reconstructions and provide experimental demonstrations.