Application of range migration algorithms to imaging with a dynamic metasurface antenna

Pulido-Mancera, Laura; Fromentèze, Thomas; Sleasman, Timothy; Boyarsky, Michael; Imani, Mohammadreza F.; Reynolds, Matthew S.; Smith, David R.

doi:10.1364/josab.33.002082

Cited by 61 publications

(87 citation statements)

References 35 publications

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“…The conventional range migration algorithm (RMA) assumes simple, dipolar antennas with well-defined phase centers-a condition not met by our dynamic metasurface aperture [73]. This issue has recently been addressed in [9] and a pre-processing technique was introduced in [47,48] to make the RMA and dynamic metasurfaces compatible. In the following, we will review this pre-processing step and then recap the salient portions of the RMA before adapting this method to the single frequency case used here.…”

Section: Image Reconstructionmentioning

confidence: 99%

“…Since GMRES acts on the total H matrix, the number of frequencies versus number of tuning states is irrelevant to its operation; thus it was the method of choice for comparing the misalignment simulations which had a variable number of frequencies (and thus a variable P). A more detailed study on the effects of SVD truncation and inversion can be found in [48].…”

Section: Gmres Vs Rma Reconstructionsmentioning

confidence: 99%

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Single-frequency microwave imaging with dynamic metasurface apertures

et al. 2017

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Conventional microwave imaging schemes, enabled by the ubiquity of coherent sources and detectors, have traditionally relied on frequency bandwidth to retrieve range information, while using mechanical or electronic beamsteering to obtain cross-range information. This approach has resulted in complex and expensive hardware when extended to large-scale systems with ultrawide bandwidth. Relying on bandwidth can create difficulties in calibration, alignment, and imaging of dispersive objects. We present an alternative approach using electrically-large, dynamically reconfigurable, metasurface antennas that generate spatially-distinct radiation patterns as a function of tuning state. The metasurface antenna consists of a waveguide feeding an array of metamaterial radiators, each with properties that can be modified by applying a voltage to diodes integrated into the element. By deploying two of these apertures, one as the transmitter and one as the receiver, we realize sufficient spatial diversity to alleviate the dependence on frequency bandwidth and obtain both range and cross-range information using measurements at a single frequency. We experimentally demonstrate this proposal by using two one-dimensional dynamic metasurface apertures and reconstructing various two-dimensional scenes (range and cross-range). Furthermore, we modify a conventional reconstruction method-the range migration algorithm-to be compatible with such configurations, resulting in an imaging system that is efficient in both software and hardware. The imaging scheme presented in this paper has broad application to radio frequency imaging, including security screening, through-wall imaging, biomedical diagnostics, and synthetic aperture radar.

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Section: Image Reconstructionmentioning

confidence: 99%

Section: Gmres Vs Rma Reconstructionsmentioning

confidence: 99%

Single-frequency microwave imaging with dynamic metasurface apertures

et al. 2017

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“…The waveguide-fed metasurface is an emerging concept for aperture antenna design that leverages resonant, subwavelength, radiating elements to generate desired radiation patterns for applications including beam forming for satellite communications [1][2][3][4], radio frequency (RF) imaging [5][6][7], wireless power transfer [8,9] and synthetic aperture imaging [10][11][12]. The use of subwavelength scattering or radiating elements over an aperture enables the effective electric and magnetic current distributions to be conceptualized as continuous, motivating a holographic design approach for the antenna as opposed to the discrete mathematics that would characterize phased arrays and electronically scanned antennas (ESAs) [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Analysis of a Waveguide-Fed Metasurface Antenna

et al. 2017

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The metasurface concept has emerged as an advantageous reconfigurable antenna architecture for beam forming and wavefront shaping, with applications that include satellite and terrestrial communications, radar, imaging, and wireless power transfer. The metasurface antenna consists of an array of metamaterial elements distributed over an electrically large structure, each subwavelength in dimension and with subwavelength separation between elements. In the antenna configuration we consider here, the metasurface is excited by the fields from an attached waveguide. Each metamaterial element can be modeled as a polarizable dipole that couples the waveguide mode to radiation modes. Distinct from the phased array and electronically scanned antenna (ESA) architectures, a dynamic metasurface antenna does not require active phase shifters and amplifiers, but rather achieves reconfigurability by shifting the resonance frequency of each individual metamaterial element. Here we derive the basic properties of a one-dimensional waveguide-fed metasurface antenna in the approximation that the metamaterial elements do not perturb the waveguide mode and are non-interacting. We derive analytical approximations for the array factors of the 1D antenna, including the effective polarizabilities needed for amplitude-only, phase-only, and binary constraints. Using full-wave numerical simulations, we confirm the analysis, modeling waveguides with slots or complementary metamaterial elements patterned into one of the surfaces.

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“…Used as coatings, metasurfaces can control the absorbance and emissivity of a surface, and thus have relevance to thermophotovoltaics [34], detectors and sources [35][36][37][38][39][40][41]. Given the capabilities of metasurfaces to control waves, but without many of the limitations of volumetric metamaterials, metasurfaces have proven a good match for commercialization efforts, with many serious applications now being pursued, including satellite communications [42][43][44], radar [45], and microwave imaging [46][47][48].…”

Section: Introductionmentioning

confidence: 99%

Polarizability extraction of complementary metamaterial elements in waveguides for aperture modeling

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We consider the design and modeling of metasurfaces that couple energy from guided waves to propagating wavefronts. This is a first step towards a comprehensive, multiscale modeling platform for metasurface antennas-large arrays of metamaterial elements embedded in a waveguide structure that radiates intro free-space-in which the detailed electromagnetic responses of metamaterial elements are replaced by polarizable dipoles. We present two methods to extract the effective polarizability of a metamaterial element embedded in a one-or two-dimensional waveguide. The first method invokes surface equivalence principles, averaging over the effective surface currents and charges within an element to obtain the effective dipole moments; the second method is based on computing the coefficients of the scattered waves within the waveguide, from which the effective polarizability can be inferred. We demonstrate these methods on several variants of waveguidefed metasurface elements, finding excellent agreement between the two, as well as with analytical expressions derived for irises with simpler geometries. Extending the polarizability extraction technique to higher order multipoles, we confirm the validity of the dipole approximation for common metamaterial elements. With the effective polarizabilities of the metamaterial elements accurately determined, the radiated fields generated by a metasurface antenna (inside and outside the antenna) can be found self-consistently by including the interactions between polarizable dipoles. The dipole description provides an alternative language and computational framework for engineering metasurface antennas, holograms, lenses, beam-forming arrays, and other electrically large, waveguide-fed metasurface structures.

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Application of range migration algorithms to imaging with a dynamic metasurface antenna

Cited by 61 publications

References 35 publications

Single-frequency microwave imaging with dynamic metasurface apertures

Single-frequency microwave imaging with dynamic metasurface apertures

Analysis of a Waveguide-Fed Metasurface Antenna

Polarizability extraction of complementary metamaterial elements in waveguides for aperture modeling

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