Addition Theorem for Digital Coding Metamaterials

Abstract

Recently, 2D versions of metamaterials, metasurfaces, have attracted more attention, [11] due to their advantages of low cost, low profile, and strong abilities to manipulate spatial and surface waves. Novel generalized sheet transition condition method [12] and transverse resonance method [13] were first presented to analyze the EM performance of metasurfaces. Then generalized Snell's law [14] was proposed to introduce the concept of abrupt phase when designing metasurfaces. By changing the size, shape, or orientation of unit cells, the abrupt phase provided by the metasurface can be tailored accordingly, and the outgoing EM waves are engineered arbitrarily. Metasurfaces have offered more convenience and freedom for manipulating EM wavefronts, and have been widely applied in the microwave, [15][16][17][18][19][20] terahertz, [21][22][23][24] visible, [25][26][27][28] and even acoustic [29,30] frequencies.Metamaterials and metasurfaces described by continuously effective medium parameters and phase distributions have powerful capabilities in controlling EM waves, but in static ways. That is to say, once a metamaterial or metasurface is fabricated, its function will be fixed. In order to reach real-time controls to EM waves, digital coding characterization has been proposed to describe metamaterial, resulting in the concepts of coding, digital, and programmable metamaterials. [31] The binary 1-bit digital codes "0" and "1" are adopted to indicate the reflection phases of 0° and 180°, from which one can manipulate EM waves using different coding sequences. The digital codes have been extended to 2-bit and more to bring more freedom for controlling scattering beams. The digital states "0." "1," "2," and "3" represent the reflection phases of 0°, 90°, 180°, and 270°, respectively.By designing a unit cell controllable by a diode to achieve either "0" or "1" state, the digital and programmable metamaterials have been realized to reach real-time manipulations to EM waves. [31] The digital coding representation links the traditional metamaterials to information theory, giving us an opportunity to control EM performance through discrete digital states. Based on these concepts, many kinds of functions such as beam steering [31][32][33] and reduction of radar crosssections [34] have been achieved by switching coding sequences on coding metamaterials in microwave and terahertz regions. Recently, the concept of anisotropic coding metamaterials has been demonstrated, which can achieve two independent coding behaviors for different polarizations. [35] Furthermore, convolution operations on coding metasurfaces were presented to Coding representation of metamaterials builds up a bridge between the physical world and the digital world, making it possible to manipulate electromagnetic (EM) waves by digital coding sequences and reach field-programmable metamaterials. Here, the coding space is extended to complex domain and proposed complex digital codes to provide closer essence of EM-wave propagation. Based on the analytic geometr...

Programmable Controls of Multiple Modes of Spoof Surface Plasmon Polaritons to Reach Reconfigurable Plasmonic Devices

“…[2][3][4][5][6] To overcome the complexity of 3D structures, an ultrathin corrugated metallic strip was proposed in 2013 to support and guide the SSPPs with high confinement even when it was bent, twisted, or wrapped arbitrarily. [21][22][23][24][25][26][27] However, only a few works for the dynamic manipulation of SSPPs have been reported at both terahertz [28][29][30] and microwave [16,[31][32][33][34][35] frequencies, and that most of them are simply tunable SSPPs rather than programmable ones. [8,9] Hereafter, many related works have been reported based on SSPPs, [10][11][12][13][14][15][16][17][18][19][20] which have advantages of low transmission loss, highly localized fields, low crosstalk, and so on.…”

“…[21][22][23][24][25][26][27] However, only a few works for the dynamic manipulation of SSPPs have been reported at both terahertz [28][29][30] and microwave [16,[31][32][33][34][35] frequencies, and that most of them are simply tunable SSPPs rather than programmable ones. [21][22][23][24][25][26][27] However, only a few works for the dynamic manipulation of SSPPs have been reported at both terahertz [28][29][30] and microwave [16,[31][32][33][34][35] frequencies, and that most of them are simply tunable SSPPs rather than programmable ones.…”

“…[8,9] Hereafter, many related works have been reported based on SSPPs, [10][11][12][13][14][15][16][17][18][19][20] which have advantages of low transmission loss, highly localized fields, low crosstalk, and so on.Recently, programmable metamaterials and metasurfaces have been developed greatly for the dynamic manipulation of electromagnetic (EM) waves, which give the possibility for a single device to possess different functionalities that can be electrically switched through field programming. [21][22][23][24][25][26][27] However, only a few works for the dynamic manipulation of SSPPs have been reported at both terahertz [28][29][30] and microwave [16,[31][32][33][34][35] frequencies, and that most of them are simply tunable SSPPs rather than programmable ones. For example, by placing the split-ring resonators (SRRs) close to the plasmonic waveguide, the resonance of the SRR will introduce a narrow rejection band, whose central frequency can be tuned by controlling the resonant response of the SRRs.…”

Flexible Manipulation of Emitting Beams Using Single‐Aperture Circularly Polarized Digital Metasurface Antennas: Multi‐Beam Radiation toward Vortex‐Beam Generation

“…As a specific branch of digital metasurfaces, multi-beam shared-aperture coding architectures [33][34][35][36] are extremely promising for point-to-multipoint data solutions, high-speed Internet applications, and military communication satellites since they enable massive angular coverage over a wide area of the earth, provide links with high precision and security between users, and cope with blockage and interference. Although significant efforts have been made to develop multi-beam digital metasurfaces from microwave [27] to terahertz [30] spectra, the most involved coding meta-atoms are naturally passive and have resorted to a horn antenna or other forms of antenna as their primary feed, which will bring some assembly problems that result in larger volume, higher system complexity, and shadow effects.…”

“…Although significant efforts have been made to develop multi-beam digital metasurfaces from microwave [27] to terahertz [30] spectra, the most involved coding meta-atoms are naturally passive and have resorted to a horn antenna or other forms of antenna as their primary feed, which will bring some assembly problems that result in larger volume, higher system complexity, and shadow effects. [27][28][29][30][31][32][33][34][35][36] More recently, X. Zhang et al designed a low-profile planar antenna array consisting of binary elements fed by a microstrip feeding network to target multifarious radiating functionalities in a more flexible routine. [37] Nevertheless, along with occupying a large space due to exploiting sparse antenna elements (with the distance of about 3 0 /2), the performance of the proposed device was restricted to the linear polarization and inevitably associated with non-negligible grating lobes.…”