Metasurfaced Reverberation Chamber

Abstract

The concept of metasurfaced reverberation chamber (RC) is introduced in this paper. It is shown that by coating the chamber wall with a rotating 1-bit random coding metasurface, it is possible to enlarge the test zone of the RC while maintaining the field uniformity as good as that in a traditional RC with mechanical stirrers. A 1-bit random coding diffusion metasurface is designed to obtain all-direction backscattering under normal incidence. Three specific cases are studied for comparisons, including a (traditional) mechanical stirrer RC, a mechanical stirrer RC with a fixed diffusion metasurface, and a RC with a rotating diffusion metasurface. Simulation results show that the compact rotating diffusion metasurface can act as a stirrer with good stirring efficiency. By using such rotating diffusion metasurface, the test region of the RC can be greatly extended.Metamaterials constitute one of the most significant and interesting topics in electromagnetic field theory. Planar metamaterials, particularly those operating in the optical domain, can be readily fabricated by means of currently available technologies, such as lithography or nano-printing methods. Such technologies allow for the implementation of single-layer or multilayer stacks of planar metamaterial structures. Planar metamaterials made by a two-dimensional (2D) array of "meta-atoms" are called metasurfaces, which can be considered to be the 2D equivalent of bulk metamaterials 1-3 . Cui et al. proposed the concept of a coding metasurface in 2014 4 , which is well suited to a variety of applications, such as the control of the radiation beams of antennas, the reduction of the scattering features of targets, and the fabrication of smart metamaterials. Diffusion coding metasurfaces have recently been proposed for radar cross section (RCS) reduction [5][6][7] . The concept of coding metasurface can also be applied in the area of electromagnetic compatibility (EMC), particularly in producing diffusive back scattering in reverberation chambers (RCs), which are well-known facilities to carry out EMC tests [8][9][10][11][12] . RCs, typically implemented by rectangular cavities, use mode stirring or mode tuning technology to change the boundary conditions of the electromagnetic fields, in order to produce a statistically uniform field distribution [13][14][15][16] . In 13 , the field uniformity is specified as a standard deviation from the mean value of the normalized maximum values obtained at each of eight locations during one rotation of the stirrer. Currently, most standard RCs are equipped with one or two mechanical stirrers in order to achieve a uniform field distribution. However, such stirrers occupy a large volume in the RC. To overcome the drawback of the size and maintenance of stirrers, the use of diffusers to enhance the scattering in the RC is proposed (note that diffusers are much smaller than stirrers) [17][18][19][20][21][22][23][24][25] . Many types of diffusers exist, including the Schroeder quadratic residue diffuser (QRD), the maximum le...

Measurement uncertainty of RC and its reduction techniques for OTA tests: a review

“…for more working volume), the metasurface technique has been applied to the RC. Sun et al in [52] use the 1 bit random coding metasurface and show improved uncertainty via simulations. Nevertheless, the effectiveness of the metasurface was demonstrated by pointing a directive antenna toward it and compare the resulting uncertainty with that of pointing the same antenna to the RC wall.…”

Coding Metasurfaces and Applications

“…To overcome the size and maintenance problems of the stirrers, it is proposed the use of diffusion metasurface in the RC to enhance the scattering. Such metasurface is much smaller than a stirrer [9]. According to the concept of coding metasurface, the designed 1-bit random coding metasurface (by employing the genetic algorithm) can provide an optimized distribution of unit cells to get a uniform backscattering (see Figure 11).…”

“…The 1-bit random coding diffusion metasurface distributions and simulated surface current distribution and near-field pattern under normal incidence. Reprinted with permission from Ref [9]…”

Enhancing the Number of Modes in Metasurfaced Reverberation Chambers for Field Uniformity Improvement

“…In all the cases, the unit cell of the metasurface reported in Ref. [ 21 , 22 , 23 ] (providing a reflection phase different from π and shown in Figure 2 ) has been used. The dimensions of the metasurface have been set to 5328 mm × 3996 mm, and the first two cases correspond to a periodic arrangement of unit cells.…”

“…The study of the cited metasurface cases, as well as the consideration of different number of metasurface walls in the RC (up to four), and the concluding remarks highlighted above, is the main original aspect of the present paper as compared to Ref. [ 23 ].…”