Single-frequency microwave imaging with dynamic metasurface apertures

Sleasman, Timothy; Boyarsky, Michael; Imani, Mohammadreza F.; Fromentèze, Thomas; Gollub, Jonah N.; Smith, David R.

doi:10.1364/josab.34.001713

Cited by 71 publications

(40 citation statements)

References 77 publications

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“…Nowadays, three types of imaging systems are widely utilized, i.e. the real-aperture (RA) system [68], the synthetic-aperture (SA) system [69] and the aperture-coded computational imager [70][71][72][73][74][75][76][77][78][79][80][81][82][83]. The RA system is composed of massive antenna elements in a large aperture, which is more flexible in measurement modes but suffers from the big size, heavy weight, high power and high expense of hardware.…”

Section: Programmable Imagermentioning

confidence: 99%

Information metamaterials – from effective media to real-time information processing systems

Cui

2019

Nanophotonics

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Metamaterials have been characterized by effective medium parameters over the past decades due to the subwavelength nature of meta-atoms. Once the metamaterials are fabricated, their functions become fixed or tunable. Recently, the concept of digital metamaterials has been introduced, in which, for instance, the constitutive 1-bit meta-atom is digitalized as “0” or “1” corresponding to two opposite electromagnetic (EM) responses. The digital metamaterials set up a bridge between the physical world and the information world. More interestingly, when the digital meta-atom is programmable, a single metamaterial can be used to realize different functions when programmed with different coding sequences. Moreover, as the states of programmable meta-atoms can be quickly switched, it enables the wave-based information coding and processing on the physical level of metamaterials in real time. For these reasons, we prefer to call digital metamaterials with programmable meta-atoms as “information metamaterials.” In this review article, we introduce two basic principles for information metamaterials: Shannon entropy on metamaterials to measure the information capacity quantitatively and digital convolution on metamaterials to manipulate the beam steering. Afterwards, two proof-of-concept imaging systems based on information metamaterials, i.e. programmable hologram and programmable imager, are presented, showing more powerful abilities than the traditional counterparts. Furthermore, we discuss the time-modulated information metamaterial that enables efficient and accurate manipulations of spectral harmonic distributions and brings new physical phenomena such as frequency cloaking and velocity illusion. As a relevant application of time-modulated information metamaterials, we propose a novel architecture of wireless communication, which simplifies the modern wireless communication system. Finally, the future trends of information metamaterials are predicted.

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Section: Programmable Imagermentioning

confidence: 99%

Information metamaterials – from effective media to real-time information processing systems

Cui

2019

Nanophotonics

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“…Using the setup discussed in the subsection II-C, we examine two cases: 1) when a simple dipole antenna (an open-ended waveguide antenna) acts as the transmitter and 2) when a DMA is used as the transmitter. In the first case, we scanned a receiving antenna over an area of 0.4 m x 0.4 m (sampling resolution of 5 mm) with 801 uniform frequency points (19)(20)(21)(22)(23)(24). At each position and for each frequency point, we saved the scattering parameter between the transmitting and receiving antenna, S We have plotted examples of the scanned data for different frequency points (for the dipole antenna) and different masks (for the DMA) in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Using these DMAs, a variety of computational imaging scenarios have been reported in the literature [14], [15], [17]- [20]. A prominent example is [19] in which the multiplexing capabilities of the DMA allow for retrieving the scene information at a single frequency. In other words, the pattern diversity of the DMA was able to replace frequency or spatial diversity as is common in most computational imaging systems.…”

Section: Introductionmentioning

confidence: 99%

Generating Information-Diverse Microwave Speckle Patterns Inside a Room at a Single Frequency With a Dynamic Metasurface Aperture

et al. 2020

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We demonstrate that dynamic metasurface apertures (DMAs) are capable of generating a multitude of highly uncorrelated speckle patterns in a typical residential environment at a single frequency. We use a DMA implemented as an electrically-large cavity excited by a single port and loaded with many individually-addressable tunable metamaterial radiators. We placed such a DMA in one corner of a plywood-walled L-shape room transmitting microwave signals at 19 GHz as we changed the tuning states of the metamaterial radiators. In another corner, in the non-line-of-sight of the DMA, we conducted a scan of the field generated by the DMA. For comparison, we also performed a similar test where the DMA was replaced by a simple dipole antenna with fixed pattern but generating a signal that spanned 19 − 24 GHz. Using singular value decomposition of the scanned data, we demonstrate that the DMA can generate a multitude of highly uncorrelated speckle patterns at a single frequency. In contrast, a dipole antenna with a fixed pattern can only generate such a highly uncorrelated set of patterns when operating over a large bandwidth. The experimental results of this paper suggest that DMAs can be used to capture a diversity of information at a single frequency which can be used for single frequency computational imaging systems, NLOS motion detection, gesture recognition systems, and more. INDEX TERMS Antenna radiation patterns, radio frequency, sensors, antenna arrays, metamaterials.

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“…dispersive objects, may cause issues for image reconstruction using wideband devices, and hence single frequency data may be considered preferable. While single frequency microwave antennas are still being studied, there has been much progress in developing antennas that produce two dimensional data collection surfaces, in particular dynamic metasurface antennas [15,4]. These antennas are created to produce electrically large, linear transmit and receive apertures.…”

Section: (Communicated By Margaret Cheney)mentioning

confidence: 99%

A reproducing kernel Hilbert space framework for inverse scattering problems within the Born approximation

Muller¹

2019

Inverse Problems &Amp; Imaging

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In this work we develop a new reproducing kernel Hilbert space (RKHS) framework for inverse scattering problems using the Born approximation. We assume we have backscattered data of a field that is dependent on an unknown scattering potential. Our goal is to reconstruct or image this scattering potential. Assuming the scattering potential lies in a RKHS, we find that the imaging equation can be rewritten as the inner product of the desired unknown function with the adjoint of the forward operator applied to the kernel of the imaging operator. We therefore may choose the kernel of the imaging operator such that the adjoint applied to this kernel is precisely the reproducing kernel of the Hilbert space the reflectivity function lies in. In this way we are able to obtain an alternative definition of an ideal image. We will demonstrate this theory using synthetic aperture radar imaging as an example, though there are other applicable imaging modalities i.e. inverse diffraction and diffraction tomography [1,6]. We choose SAR as it was the motivating application for this work. We will compare the RKHS ideal imaging technique to the standard microlocal analytic ideal image from backprojection theory. Note this method requires a variation of the standard SAR data model with the assumption of a full two dimensional data collection surface as opposed to a one dimensional flight path, however we are able to perform imaging with a single frequency and avoid the approximations made in the backprojection imaging operator derivation.1. Introduction. In this paper we develop a new reproducing kernel Hilbert space framework for inverse scattering problems using the Born approximation. We assume we have backscattered data of some field that is dependent on an unknown scattering potential. Our goal is to reconstruct or image this scattering potential. We will use synthetic-aperture radar imaging as an example to demonstrate the theory developed in this work in terms of a real application.There are two main mathematical tasks to consider for imaging, first developing a forward model and then creating a method to invert that model to obtain information about the unknown function of interest. We will assume our collected data is in the form of a scattered field which is related to an unknown function to be reconstructed. We will therefore assume our field of interest satisfies the inhomogeneous scalar wave equation in the time domain and the inhomogeneous Helmholtz equation in the frequency domain. Thus we may use a Green's function

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Single-frequency microwave imaging with dynamic metasurface apertures

Cited by 71 publications

References 77 publications

Information metamaterials – from effective media to real-time information processing systems

Information metamaterials – from effective media to real-time information processing systems

Generating Information-Diverse Microwave Speckle Patterns Inside a Room at a Single Frequency With a Dynamic Metasurface Aperture

A reproducing kernel Hilbert space framework for inverse scattering problems within the Born approximation

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