Electromagnetic waves undergo multiple uncontrollable alterations as they propagate within a wireless environment. Free space path loss, signal absorption, as well as reflections, refractions, and diffractions caused by physical objects within the environment highly affect the performance of wireless communications. Currently, such effects are intractable to account for and are treated as probabilistic factors. This article proposes a radically different approach, enabling deterministic, programmable control over the behavior of wireless environments. The key enabler is the so-called HyperSurface tile, a novel class of planar meta-materials that can interact with impinging electromagnetic waves in a controlled manner. The HyperSurface tiles can effectively re-engineer electromagnetic waves, including steering toward any desired direction, full absorption, polarization manipulation, and more. Multiple tiles are employed to coat objects such as walls, furniture, and overall, any objects in indoor and outdoor environments. An external software service calculates and deploys the optimal interaction types per tile to best fit the needs of communicating devices. Evaluation via simulations highlights the potential of the new concept.

pdf/a-new-wireless-communication-paradigm-through-software-4b07ofxmm9.pdf

A New Wireless Communication Paradigm through Software-Controlled Metasurfaces

Electromagnetic waves undergo multiple uncontrollable alterations as they propagate within a wireless environment. Free space path loss, signal absorption, as well as reflections, refractions and diffractions caused by physical objects within the environment highly affect the performance of wireless communications. Currently, such effects are intractable to account for and are treated as probabilistic factors. The paper proposes a radically different approach, enabling deterministic, programmable control over the behavior of the wireless environments. The key-enabler is the so-called HyperSurface tile, a novel class of planar meta-materials which can interact with impinging electromagnetic waves in a controlled manner. The HyperSurface tiles can effectively re-engineer electromagnetic waves, including steering towards any desired direction, full absorption, polarization manipulation and more. Multiple tiles are employed to coat objects such as walls, furniture, overall, any objects in the indoor and outdoor environments. An external software service calculates and deploys the optimal interaction types per tile, to best fit the needs of communicating devices. Evaluation via simulations highlights the potential of the new concept.

A New Wireless Communication Paradigm through Software-controlled Metasurfaces

Based on polarization conversion and destructive interference, a novel monolayered metasurface is proposed for ultrawideband monostatic and bistatic radar cross section (RCS) reductions for both copolarization and cross polarization. Unit cells share a simple asymmetric double arrow shape, but with variable geometry parameters, correspondingly with different polarization conversion capabilities and different reflection coefficients. The particle swarm optimization (PSO) algorithm and array theory are combined to optimize and select appropriate parameters for unit cells. The optimized unit cells (O-cells) simultaneously realize the polarization conversion and destructive interference to reduce copolarized RCS. In addition, mirrors of these O-cells (M-cells) are adopted to achieve the complete destructive interference to reduce cross-polarized RCS. Therefore, the total monostatic RCS can be greatly reduced. To improve the bistatic RCS reduction, random distribution of unit cells is carefully designed to realize diffusion patterns. In both the simulation and measurement results, a 10 dB monostatic RCS reduction at the normal incidence is achieved from 7.5 to 22.5 GHz (100% bandwidth). Furthermore, good specular and bistatic RCS reduction performances under oblique incident waves are also obtained. The proposed methodology opens up a new route for ultrawideband RCS reduction.

Ultrawideband Monostatic and Bistatic RCS Reductions for Both Copolarization and Cross Polarization Based on Polarization Conversion and Destructive Interference

In this letter, a novel coding metasurface (CM) based on low Q resonators and fast optimization method is proposed to achieve wideband radar cross section (RCS) reduction of the microstrip antenna array (MAA) while maintaining its radiation properties. Theoretical analysis reveals the relationship between the Q value and the phase shift of the resonator, which indicates that the wideband control of the reflected wave can be achieved with the low Q resonator. Moreover, the fast optimization method based on the convolution theorem is proposed, which enhances the optimization efficiency of the coding matrix. Finally, the CM with two kinds of low Q resonators is constructed and applied to the MAA for wideband RCS reduction. The measured results indicate that the proposed low RCS MAA (LRMAA) can realize more than 10 dB RCS reduction in 5.8–21.5 GHz, which also demonstrates superior specular scattering suppression. In parallel, the radiation properties of the LRMAA are consistent with those of MAA. The proposed strategy achieves the high integration of radiation and scattering properties, which has potential applications in antenna systems of stealth platforms.

Wideband RCS Reduction of Microstrip Antenna Array Using Coding Metasurface With Low Q Resonators and Fast Optimization Method

In recent years, metasurface (MTS) arrays have shown promising abilities to control and manipulate electromagnetic (EM) waves through modified surface boundary conditions. The constituent unit elements of a MTS have become increasingly complex with rise of anisotropic radio-frequency (RF) applications such as beam scanning through anomalous reflection/refraction, beam focusing, and polarization conversion in an extremely low-profile. Designing these meta-atoms or metagratings is a challenging and time-consuming procedure. Each new MTS design typically requires numerous iterations of manual tuning and full-wave simulations. In this paper, we employ deep convolutional generative adversarial networks (DC-GANs) to generate anisotropic RF metamaterial unit cell designs for MTS arrays. Using a small set of simulated meta-atom spectra, these networks learn the relationship between the physical structure of meta-atoms and their reflection spectra for vertical and horizontal polarizations. Our numerical experiments demonstrate that DC-GANs are able to generate meta-atom structures that resemble design features in the training data. Numerical experiments with design test case showed 90% accurate reflection responses with errors within 0.2 (1.3) dB in magnitude and 3.0° (4.4°) in phase for the co-polar (cross- polar) component.

RF Metasurface Array Design Using Deep Convolutional Generative Adversarial Networks

In this paper, an ultra-wideband, wide angle and polarization-insensitive metasurface is designed, fabricated, and characterized for suppressing the specular electromagnetic wave reflection or backward radar cross section (RCS). Square ring structure is chosen as the basic meta-atoms. A new physical mechanism based on size adjustment of the basic meta-atoms is proposed for ultra-wideband manipulation of electromagnetic (EM) waves. Based on hybrid array pattern synthesis (APS) and particle swarm optimization (PSO) algorithm, the selection and distribution of the basic meta-atoms are optimized simultaneously to obtain the ultra-wideband diffusion scattering patterns. The metasurface can achieve an excellent RCS reduction in an ultra-wide frequency range under x- and y-polarized normal incidences. The new proposed mechanism greatly extends the bandwidth of RCS reduction. The simulation and experiment results show the metasurface can achieve ultra-wideband and polarization-insensitive specular reflection reduction for both normal and wide-angle incidences. The proposed methodology opens up a new route for realizing ultra-wideband diffusion scattering of EM wave, which is important for stealth and other microwave applications in the future.

/pdf/ultra-wideband-wide-angle-and-polarization-insensitive-3imo60llxm.pdf

Ultra-wideband, Wide Angle and Polarization-insensitive Specular Reflection Reduction by Metasurface based on Parameter-adjustable Meta-Atoms.

/pdf/specular-reflection-reduction-bymetasurface-based-on-4z4dmhom6a.pdf

Specular Reflection Reduction byMetasurface based on ParameteradjustableMeta-Atoms

Specular Reflection Reduction by Metasurface based on Parameteradjustable Meta-Atoms

In this paper, a metasurface (MS) is designed based on the hybrid array pattern synthesis and particle swarm optimization method for wideband monostatic and multistatic radar stealth. The non-absorptive MS is composed of two kinds of electronic band gap structures with the reflection phase difference of 180° (±37°) over a wide frequency range. Far field scattering pattern of the MS can be quickly and accurately synthetized by the method of moments and array pattern synthesis. A new strategy is proposed for realizing the diffusion reflection of electromagnetic waves by redirecting electromagnetic energies to more directions through optimizing the reflected phase arrangement for the MS by hybrid array pattern synthesis and particle swarm optimization algorithm. Due to the non-uniform distributions of phase gradient between neighboring lattices, numerous scattering lobes are produced in the upper half-space, leading to a great reduction of bistatic radar cross section (RCS). The −10 dB RCS reduction bandwidth of 80.2% is achieved for both monostatic and bistatic at normal incidence. The specular reflection and bistatic scattering for oblique incidence with TE and TM polarizations are also considered in detail. The measured results are in good agreement with the corresponding simulations.

Fast analysis and optimal design of metasurface for wideband monostatic and multistatic radar stealth

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Ultra-wideband, Wide Angle and Polarization-insensitive Specular Reflection Reduction by Metasurface based on Parameter-adjustable Meta-Atoms.

Specular Reflection Reduction byMetasurface based on ParameteradjustableMeta-Atoms

Specular Reflection Reduction by Metasurface based on Parameteradjustable Meta-Atoms

Fast analysis and optimal design of metasurface for wideband monostatic and multistatic radar stealth