Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Beam Divergence Reduction of Vortex Waves with a Tailored Lens and a
  Tailored Reflector   In this paper, we present a tailored lens and a tailored reflector in order
to reduce the large beam divergence inherent to Orbital Angular Momentum waves
(OAM waves-Vortex waves) that are generated by an Uniform Circular Patch
Antenna Array (UCA) at 10 GHz. The tailored lens and the tailored reflector are
designed by the shape function (5) and (9) around the antenna s center axis,
respectively. The tailored lens is compared to UCA without and with
conventional lens. The simulated and measured results show a significant
improvement when using the tailored lens. Following, a tailored reflector is
implemented and compared to UCA without and with conventional reflector.
Firstly, the two reflectors are simulated with an impressed field source to
neglect the influence of the UCA. The simulated results of the two reflectors
show that the tailored reflector has a better performance than the conventional
reflector when the height of the reflector $r_0$ is less than around 1.5
$\lambda$ and when the opening angle of the reflector theta is less than
38{\deg} (for UCA with $d$ of $\lambda/2$). In addition, the reflectors are
simulated with real UCA with different shapes of PCB, which can disturb the
reflected waves from the reflector. Two lenses and two reflectors are
manufactured and measured in an anechoic chamber and compared to the simulation
results. This paper shows that the vortex waves needs a special lens or a
special reflector to reduce effictively the beam divergence especially when the
radius of the UCA is very large.

13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn