1. Frequency-Diverse Apertures for Computational Microwave Imaging
Frequency-diverse apertures are defined by their ability to generate spatially-distinct radiation patterns as a function of driving frequency. These complex waveforms can be used to illuminate an entire imaging domain and encode its spatial content into simple backscatter frequency measurements. The resulting signals are post-processed through computational techniques to obtain high-quality images of the scene. In this manner, frequency-diverse apertures can replace cumbersome and cost-prohibitive systems, such as systems based on mechanical raster scanning and electrical beamforming, while obtaining comparable image quality within a fraction of the acquisition time.
J. N. Gollub, O. Yurduseven, K. P. Trofatter, D. Arnitz, M. F. Imani , T. Sleasman, M. Boyarsky, A. Rose, A. Pedross-Engel, H. Odabasi, T. Zvolensky, G. Lipworth, D. Brady, D. L. Marks, M. S. Reynolds and D. R. Smith, , Large Metasurface Aperture for Millimeter Wave Computational Imaging at the Human-Scale , Sci. Rep. 7, 42650.
T. Sleasman, M. F. Imani , O. Yurduseven, K. P. Trofatter, V. Gowda, D. L. Marks, J. L. Gollub, D. R. Smith, Near Field Scan Alignment Procedure for Electrically-Large Apertures , in IEEE Transactions on Antennas and Propagation , vol.PP, no.99, pp.1-1.
M. F. Imani, T. Sleasman, J. N. Gollub, and D. R. Smith, Analytical modeling of printed metasurface cavities for computational imaging, in Journal of Applied Physics 120, 144903 (2016).
G. Lipworth, A. Rose, O. Yuduseven, V. R. Gowda, M. F. Imani, H. Odabasi, P. Trofatter, J. Gollub, and D. R. Smith, Comprehensive Simulation Platform for a Metamaterial Imaging System, Appl. Opt. 54, 9343-9353 (2015).
M. F. Imani*, T. Fromenteze*, O. Yurduseven*, J. Gollub*, C. Decroze, D. Carsenat, and D. R. Smith, Computational Imaging Using a Mode-mixing Cavity at Microwave Frequencies, Applied Physics Letters, Vol. 106 , 194104, 2015. (* These authors contributed equally to this work)
O. Yurduseven, M. F. Imani, H. Odabasi, J. Gollub, G. Lipworth, A. Rose, and D. R. Smith, Resolution of the frequency diverse metamaterial aperture imager, Progress In Electromagnetics Research, Vol. 150, 97-107, 2015.
2. Dynamic Metasurfaces for Microwave Imaging
Metasurfaces have shown great promise in sculpting electromagnetic waveforms. This capability can be much expanded by incorporating tuning mechanisms. In most dynamic metasurfaces reported in the literature, the same tuning signal is applied to the aperture, thus changing the aperture overall response. In this research thrust, we design metasurfaces such that we can address each individual element, enabling a much larger design space. Using this methodology, we have designed dynamic metasurfaces that can generate spatially-distinct radiation patterns as a function of stimuli signal. This device is an ideal platform for computational imaging which does not require large frequency bandwidth (inherent to frequency diverse apertures). Most recently, we have been able to modify range migration algorithm, commonly used in Synthesic Aperture Radar, to be utilized in systems based on dynamic metasurfaces. This is a vital step toward an imaging system which is simple and fast on both hardware and software aspects.
T. Sleasman, M. Boyarsky, M. F. Imani, T. Fromenteze, J. Gollub, and D. R. Smith, Single-frequency microwave imaging with dynamic metasurface apertures, Journal of Optical Society of America B, 34, 1713-1726, July 2017.
M. Boyarsky, T. Sleasman, L. Pulido-Mancer, T. Fromenteze, A. Pedross-Engel, C. M. Watts, M. F. Imani, M. Reynolds, and D. R. Smith, Synthetic Aperture Radar with Dynamic Metasurface Antennas: A Conceptual Development, Journal of Optical Society of America A, 34, A22-A36 March 2017.
I. Yoo, M. F. Imani, T. Sleasman, and D. R. Smith, Efficient complementary metamaterial element for waveguide-fed metasurface antennas, Optics Express Vol. 24, Issue 25, pp. 28686-28692 (2016).
M. F. Imani*, T. Sleasman*, J. N. Gollub, and D. R. Smith, Microwave Imaging Using a Disordered Cavity with a Dynamically Tunable Impedance Surface, Phys. Rev. Applied 6, 054019 – Published 29 November 2016. (* These authors contributed equally to this work)
L. Pulido-Mancera, T. Fromenteze, T. Sleasman, M. Boyarsky, M. F. Imani , M. Reynolds, and D. Smith, Application of range migration algorithms to imaging with a dynamic metasurface antenna, J. Opt. Soc. Am. B 33, Issue 10, pp. 2082-2092 (2016).
T. Sleasman, M. Boyarsky, M. F. Imani, J. N. Gollub, and D. R. Smith, Design considerations for a dynamic metamaterial aperture for computational imaging at microwave frequencies, J. Opt. Soc. Am. B 33, 1098-1111 (2016).
T. Sleasman, M. F. Imani, J. N. Gollub, and D. R. Smith, Dynamic metamaterial aperture for microwave imaging, Applied Physics Letters 107, no. 20 (2015): 204104.
T. Sleasman, M. F. Imani, W. Xu, J. Hunt, T. Driscoll, M. S. Reynolds, and D. R. Smith, Waveguide-Fed Tunable Metamaterial Element for Dynamic Apertures, in IEEE Antennas and Wireless Propagation Letters, vol. 15, no. , pp. 606-609, 2016.