Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Angle-Dependent Phase Shifter Model for Reconfigurable Intelligent
  Surfaces: Does the Angle-Reciprocity Hold?   The existing phase shifter models adopted for reconfigurable intelligent
surfaces (RISs) have ignored the electromagnetic (EM) waves propagation
behavior, thus cannot reveal practical effects of RIS on wireless communication
systems. Based on the equivalent circuit, this paper introduces an
angle-dependent phase shifter model for varactor-based RISs. To the best of our
knowledge, this is the first phase shifter model which reveals that the
incident angle of EM waves has influence on the reflection coefficient of RIS.
In addition, the angle-reciprocity on RIS is investigated and further proved to
be tenable when the reflection phase difference of adjacent RIS unit cells is
invariant for an impinging EM wave and its reverse incident one. The
angle-dependent characteristic of RIS is verified through full-wave simulation.
According to our analysis and the simulation results, we find that the
angle-reciprocity of varactor-based RIS only holds under small incident angles
of both forward and reverse incident EM waves, thus limits the channel
reciprocity in RIS-assisted TDD systems.

21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph