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Iershova
Iryna
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Faculty: |
Radio
Engineering and
special Training |
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Training
direction: |
information
security
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Theme
of master's work: |
Research
of helical
antennas with controllable characteristics in information protection
systems |
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Scientific: |
Ph.D,
Associate Professor
Paslyon Vladimir |
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Abstract of master's work:
"Research of helical antennas with controllable characteristics in
information protection systems"
Introduction
Antenna
technology has now reached a level of maturity and its development in
recent years is not primarily aimed on the creation of fundamentally
new types of antennas, but on the research of ways to improve their
performance and the use of new materials .
Development of various branches of electronics (radio reconnaissance,
radio countermeasure, radio communications with mobile objects, radio,
etc.) led to the practical need for antennas that provide the emission
and reception of electromagnetic waves with circular polarization in a
wide frequency range. Due to the fact, that the main part of the
electromagnetic energy is reflected from the antenna systems, they
become noticeable to the radio-electronic means. Therefore, nowadays,
the development of technologies to reduce the visibility (Stealth
tehnology) is gaining popularity. Stealth technology is a set of
methods to reduce the visibility of antenna systems in radio, infrared
and other gamuts of the detection spectrum through specially designed
geometrical shapes, radar absorbing materials and coatings for reducing
power and reflected signal in the direction of the emission source, and
thus remain unnoticed.
Spiral antennas occupy an important place among the various types of
broadband antennas. Spiral antennas are low and intermediately directed
elliptical wideband antennas with controlled polarization.
Directional properties of a helical antenna depend strongly on the
diameter of the helix. Antenna is omni-directional in the case the
diameter of the helix is less 0,18 λ, and when the diameter of
the helix reaches (0,25 - 0,45) λ, antenna creates emission
along the direction of motion of the wave current, ie directional
antenna. [1.222]
In foreign literature, this directional emitter is known under
different names, but most often appears under the name Helix Beam,
going back to H. Chireix (1930).
The purpose and tasks of research
The
purpose of master's work is the development of broadband spiral
antennas, unnoticeable for the detection by radio-electronic means of
intelligence, by reducing the effective dispersion area (EDA).
To achieve this goal the following tasks must be performed in the
master's work:
- Investigation of radio deception methods.
- A comparative analysis of helical
antennas’ properties and the selection of the helical antenna
satisfying such conditions.
- Simulation of broadband helical antenna.
- The calculation of helical antenna
parameters according to simulation results.
- Experimental confirmation of the data
received.
Topic relevance:
Attempts
to solve the problem of eqipment creation, invisible for
radio-electronic devices, took place since the beginning of radio
interception. In this regard, the radiocamouflage term appeared.
(radiocamouflage - a set of technical and organizational measures
aimed at enemy radio reconnaissance effectiveness reducing).
Thus, the topic of object protection (helical antennas) against
radio-electronic means of detection remains relevant today.
Expected scientific innovation.
The improved model of a plane cophased helical antenna development,
which main feature is masking from detection by radio-electronic
facilities (REF).
.
HELICAL ANTENNA
The
difference of helical antenna from other antennas with the directed
emission, primarily it the fact that its emission field is circularly
polarized. In the case of such an antenna the necessarity
of both the transmitting and receiving antennas have circular
polarization appears.
Circular polarization occurs when the conductor is wound in the
direction of emission in the form of a spiral, while total length of
wire in a turn is equal to 1 λ which, taking into account the
velocity factor , corresponds to the coil diameter D, equal to
approximately 0,31 λ. It is assumed that for the circular
polarization is used at least three turns, as the polarization of the
emission will be closer to the circular, the more turns antenna has.
Simple helical antenna emits in both directions in the direction of its
axis. To get a one-sided emission and increase the gain of the antenna
disk reflector is used. [8,254]
ULTRAWIDEBAND ANTENNA
The
term UWB antenna means that the properties of the antenna, primarily
its input impedance, directivity pattern (DP) and the directional
coefficient (DC), vary within the prescribed limits in a very wide
frequency band. [2.182]
Highly
directive antenna features.
Increasing the range of high gain antenna is an important task of
modern antenna technology.
Frequency properties of high gain antenna are determined by the
frequency properties of the interior of the antenna (power tract, feed,
controls, etc.) and the fields interference emitted by individual
elements of the antenna in outer space. The influence of the first
cause can be greatly weakened with the use of broadband channels power,
broadband irradiator, special compensating circuits and devices
development, etc. At the same time the effective ways to eliminate the
frequency dependence of the DP, related to the fields interference from
different parts of the antenna are not yet developed. Even in a
flat-phased antenna, with the change of λ, the DP form is
preserved, but its width and antenna DC change. Even worse is the
situation in the antenna array, where with the change of the
wavelength, changes both the direction of the main peak and the shape
of the DP. [2,187]
Conical
and flat helical antenna.
Conical helical antenna (Fig. 1) has the best range properties than the
cylindrical helical antennas.
Fig. 1. Conical helical
antenna
Axial emission of such antennas is formed not by the whole antenna, but
only by the active region, ie coils with the length close to λ.
With the frequency change, the active region moves along the axis of
the antenna. Flat helical antennas, including antennas in the form of
an Archimedean spiral (Fig. 2 a), are widely used. Double helical
antenna can be produced by printing and is stimulated by a wire line or
coaxial cable laid along one of the arms (along the other arm single
cable is laid to maintain symmetry, Fig. 2, b). The antenna can be
considered as a wire line rolled into a spiral, currents in adjacent
coils in the initial part of the antenna are in opposite phase and
therefore don’t emit. With the removal from power outlets, phase
shift between currents in adjacent coils is reduced due to the path
difference.
Fig. 2 Flat helical antennas
Indeed, the elements 1 and 2, located on either side of the
circle of radius r0 at the different spirals have a path difference
equal to half the length of this circle, i.e. Δr = 2πr0 Given
the antiphase excitation phase difference between elements 1 and 2
equals ψ = kΔr + π. At r0 = λ/2π value ψ =
2π, i.e. neighbor coils are excited in-phase mode traveling wave.
These turns form the emission field with circular polarization in the
direction of the antenna, which is maintained over a wide frequency
band. The lower frequency is determined by the outside diameter of the
helix, and the top – by the accuracy of antenna realization near
the feed points.
Directivity pattern consists of two broad lobes oriented
perpendicularly to the plane of the spiral. It’s also possible to
get a unidirectional emission of the spiral, by putting the screen
behind it (usually at a distance of λ0 / 4, where λ0 -
the wavelength at an average frequency range), but the presence of the
screen reduces the work frequency band.
Construction
of the spiral of Archimedes
- Divide the radius of the circle to the
same number of equal parts (8 in this example).
- Divide the circle into the same number of
equal parts.
- Line the rays from the center of the
circle through the points of division.
- On the first ray mark one radius notch.
- On the second beam mark two divisions
radius, etc.
- If you build it on, then the beam 1 8+1
marks are to be made (we get the point IX).
- On the second line of division mark 8 +2
radius (we get the X point).
- On the third line of division mark 8 +3
radius (we get the XI point), etc.
This figure is
animated, and it illustrates the construction of the spiral of
Archimedes. Size-113 kb, the number of frames -4, the number of
cycles -7.
Conclusion
At the present time flat and
conical spiral antennas with a constant pitch (Archimedean spiral) and
equi-angled hemispherical helical antennas found practical use.
Sufficiently researched the single-threaded spiral antennas with a
constant angle of winding on the surface of a paraboloid of rotation
and double-threaded spiral antennas winded on the surface of an
ellipsoid of rotation. Quasifreqency-independent two-way winding
helical antennas, helical dielectric antenna impedance have not yet
been researched as far as can be seen in the literature.
Theory of helical structures of complex shape is not developed
currently, so their properties can be guessed only approximately,
basing on the principle of local equivalence.
Sources:
- Антенны УКВ /Под
ред. Г.З. Айзенберга. В 2-х ч. Ч. 2. - М.: Связь,
1977. - 288с. с ил.
- Антенны: (Современное
состояние и
проблемы)/ Под ред. чл.-корр. АН СССР Л.Д. Бахраха и проф. Д.И.
Воскресенского.- М.: Сов. Радио, 1979.-208с
- Антенно-фидерные
устройства и
распространение радиоволн: Учебник для вузов/ Г.А. Ерохин,
О.В. Чернышев и др.; Под ред. Г.А. Ерохина. – 3-е изд., - М.:
Горячая линия-Телеком,2007.-491с.: ил.
- Жук М.С., Молочков
Ю.Б.
Антенно-фидерные устройства. М.: Энергия, 1966.
- Бекетов В.И. Антенны
сверхвысоких
частот: М.: Военное издательство министерства обороны союза ССР, 1957.
- Марков Г.Т., Сазонов
Д.М. Антенны:
Учебник для студентов радиотехнических специальностей вузов. 2-е
изд., перераб. И доп. М.:
Энергия, 1975.
- Палий
А.И. Радиоэлектронная борьба. - 2-е изд., перераб. и доп. - М.:
Воениздат, 1989. - 350с., ил
- Ротхаммель К. Антенны:
Пер. с нем.
– 3-е изд., доп. – М.: Энергия, 1979. –
320 с., ил.
- Ротхаммель К., Кришке
А. Антенны. Том
2: Пер. с нем. – Мн.: ОМО «Наш город»,
2001. -416с.: ил.
- Юрцев О.А., Рунов А.В.
«Спиральные антенны.» М.: «Сов.
радио»,1974,224 с.
- http://www.radioman-portal.ru/magazin/radio/1969/2.php
журнал "Радио"№2
, 1969г
- http://www.q-par.com/Электронный ресурс
Q-par Angus Ltd IDEAS ENGINEERED
Important
note: By the time this abstract was made, the master work is not yet
completed. Final completion date: December 2011. Full text of the
materials can be obtained from the author or his principal after that
date.
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