Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the End-Fire (Super) Directivity of an Array of Two Elementary
  Dipoles   The concept of source currents of a radiating source can be employed to
express directivity in some particular cases analytically. For an antenna
array, this concept can be combined with concepts of mutual radiation intensity
and the mutual power of array elements. Using these approaches, we treat the
evaluation of the directivity for an elementary dipole, and its end-fire array,
which is of special attention due to superdirective properties. A closed form
expression for the directivity of this array with out-of-phase excitation is
derived. It is observed that end-fire directivity can be further enhanced by
optimizing the excitation currents of the array. Their optimal relative phase
and corresponding increased directivity are also found analytically. The
results are validated by a full-wave simulator.

14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin