**1. Introduction**

Dipole and loop antennas are used in communication lines, in radar and navigation systems, TV and other fields of radio-engineering. Structures of antennas depend on their bandwidth. In VHF, UHF, L and S ranges, these antennas are made, as a rule, of conductors with a radius *Ao* (λ – wavelength in the air). Further, we will study wire dipole and loop antennas. Dipole and monopole antennas [Balanis, 1997; Markov, 1960], a Yagi-Uda antenna [Volakis, 2007; Aisenberg, Jampolsky and Terjoshin, 1977), bicone and discone antennas [Drabkin and Zuzenko, 1961], loop antennas consisting of one or two loops located in one plane [Rothammels, 1995] are well known. The length of a loop perimeter is *L* . This ensures tuning of the antenna in resonance (a reactive part of input resistance is 0) *Xr* . To reduce sizes of dipole antennas, conductor with surface reactive resistance is used. Such a conductor can be implemented, for example, in the form of a cylindrical helix with a radius *A* [Yurtsev, Runov and Kazarin, 1974]. To tune antennas in resonance, reactive resistances are used. Linear arrays of dipole antennas with series excitation are described briefly [Rothammels, 1995].

In communication nodes and antenna arrays, dipole and loop antennas function in the conditions of strong coupling. Therefore, one of the problems of numerical simulation is the research into the influence of interaction on the electrical characteristics of antennas.

Scattering characteristics of antennas are a strong factor that facilitates radar reconnaissance. These characteristics of loop and dipole antennas have hardly been studied in the literature.

In the literature, there is no enough information or there is no information at all about a number of questions related to research into and the versions of construction of dipole and loop antenna. The following is related to these problems:

© 2012 Yurtsev and Ptashinsky, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Numerical Simulations of Radiation and Scattering Characteristics of Dipole and LOOP Antennas 159

, (3)

*<sup>R</sup>* . (4)

, (5)

is the wavelength of the field

. Coordinates of the

<sup>o</sup> <sup>p</sup> ( ) ( (l ), ) *os Ul E l <sup>p</sup>* 

is the wave number of free space,

is the vector of the extraneous electric field that excites the conductor.

The remaining quantities included in (1) – (4) are shown in fig. 1.

shape is divided into M rectilinear segments of length *L*

*Zsn* is the surface resistance in a segment with number n;

*mI* is the sought current in a segment with number m. The matrix coefficients are determined by the expression:

Kmn ( , )( , )

*n m*

*L L*

, *n m L L* are the lengths of segments with numbers n and m;

G(l , ) <sup>p</sup>

*q <sup>e</sup> <sup>l</sup>*

When solving an integral equation by the method of moments, a conductor of arbitrary

beginning ( 1 , 1 , 1 *XYZ mmm* ) and the end ( 2 , 2 , 2 *XYZ mmm* ) of each segment are calculated (m

The use of impulse basis and weight functions leads to the following system of linear

M m m 1 I *ZZ K U sn lk mn n* 

*Zlk* is the series load resistance of a conductor, *k* is the number of a segment, to which the

*p q on om q p mn mn*

, (6)

*Z l l l S dl dl A B*

are unit vectors, tangent to a conductor in the centre of segments with numbers n

M is the number of segments, into which the whole conductor of length L is divided; m is the number of a segment, in which point Q (source point) is located (fig. 1), 1 *m M* ; n is the number of a segment, in which point P (point of observation) is located (fig. 1),

*ikR*

where *i* 1 ;

*Eos* 

<sup>2</sup> *<sup>k</sup>* 

is the segment number, 1 *m M* ).

algebraic equations:

where

1 *n M* ;

where

*l S on om* , 

and m;

resistance is connected;

that excites the conductor;

Green's function is defined by the expression:


The above specified questions are the contents of the present chapter.
