Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A metamaterial ring with applications in broad band antennas used in
  radio astronomy and satellite communications   Electromagnetic metamaterials at microwave frequencies are well established
in industry and research. Recent work has shown how a specific kind of metallic
metamaterial can contribute towards improving the performance of the feedhorn
antennas used in radio astronomy and satellite telecommunications. In this
article, we justify this argument, finding an innovative type of meta-ring of
remarkable manufacturability with a potential to improve the state of the art
in these fields. A pioneering meta-horn antenna formed of meta-rings is then
fabricated and characterized in the laboratory, showing an excellent feature on
an octave bandwidth, especially in terms of cross-polarization, a key figure of
merit in both radio astronomy and telecommunications; and also side-lobe level,
return-loss and gain.

5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol