1. Spiral Antenna
Prepared By:
Abd El Hakim Ali Elagori
T.C.
ISTANBUL AYDIN UNIVERSITY
COLLEGE OF ENGINEERING AND TECHNOLOGY Department of Electrical &
Electronic Engineering
14/4/2016
2. Outlines
Introduction
History of the spiral antenna
Bandwidth of the antenna
Polarization
Gain
Type of spiral antenna
Some parameter design
Application
Conclusion
3. antennas
The IEEE Standard Definitions of
Terms for Antennas (IEEE Std 145–1983) ∗
defines the antenna or aerial as “means
for radiating or receiving radio waves.”
4. History
In 1954, Edwin Turnur started messing with a dipole
antenna. Instead of leaving the arms straight, he
wrapped them around each other, forming a spiral.
This was the beginning of the spiral antenna
dipole antenna spiral antenna
5. Bandwidth of the spiral antenna
Spiral antennas belong to the class of "frequency
independent" antennas; these antennas are
characterized as having a very large bandwidth.
The Bandwidth can be as high as 30:1
This means that if the lower frequency is 1 GHz, the
antenna would still be efficient at 30 GHz, and every
frequency in between.
6. Also we can say that the highest frequency is thirty times
greater then the lowest frequency
Bandwidth of the spiral antenna
Spiral antennas belong to the class of "frequency
independent" antennas; these antennas are
characterized as having a very large bandwidth.
The Bandwidth can be as high as 30:1
This means that if the lower frequency is 1 GHz, the
antenna would still be efficient at 30 GHz, and every
frequency in between.
7. Polarization of the spiral antenna
Spiral antennas are usually circularly polarized. The
spiral antenna’s radiation pattern typically has a
peak radiation direction perpendicular to the plane
of the spiral (broadside radiation).
This is a very broad beam width for circular
polarization; this is one of the features that makes
spiral antennas very useful.
A left-handed- CCW
circularly polarized wave
A right-handed- CW
circularly polarized wave
8. The Spiral Antenna has circular polarization over a wide beamwdith,
often for angular regions as wide as
.
The Half-Power Beam width (HPBW) is approximately 70-90
degrees.
Radiation Patterns
9. The radiation pattern of the Log-Periodic Spiral Antenna is approximately given
by:
Directivity 3D plot of radiation pattern
10. Input impedance
Spiral antennas have input impedance
approximately Zin≤200Ω
This figure show the input impedance of the two arms spiral
antenna is approximately constant with varying the
frequency. Research was done in [5]
14. ➢ The Archimedean spiral antenna is a popular of
frequency independent antenna . And it has two arms
Each arm of an Archimedean spiral is linearly
proportional to the angle, φ, and is described by the
following relationship
➢ Each arm of the Archimedean spiral is defined by the
equation
Where:
r1:is the inner radius of the spiral
r2 :is the outer radius of the spiral
W: is the width of each arm
S: the spacing between each turn
Archimedean Spiral Antenna
15. The low frequency operating point of the spiral is determined theoretically
by the outer radius and is given by
And the high frequency operating point is based on the inner radius giving
Where : C is the speed of light 3x10^8 m/s
16. where
η is the intrinsic impedance of free space surrounding the
antenna.
The input impedance of a self-complementary antenna
can be found using Babinet’s principle, giving by :
Archimedean spiral antenna in free space the input
impedance should be
377/2=188.5Ω.
In actual realizations of Spiral antennas the impedance
tends to be less than this, in the 100-150 Ohm range.
17. Also it is known as equiangular spiral antenna
We can define the arms of a spiral antenna using simple polar
coordinates and polar functions. The log-periodic spiral antenna,
also known as the equiangular spiral antenna, has each arm
defined by the polar function
where:
R0 = constant that controls the initial
radius of the spiral antenna
a = parameter that controls the rate at
which the spiral antenna grows with
angle
The Log-Periodic Spiral Antenna
18. Axial ratio of antenna in free space
Impedance of antenna in free space
19. The parameters that effect the radiation of the spiral antenna
1.Total Length of the Spiral, or the outer radius
This determines the lowest frequency of operation for the spiral
antenna.
the highest frequency in the spiral antenna’s can be determined from the
inner radius (R0)
20. 2. Number of Turns (N) - The number of turns of the spiral
is also a design parameter. Experimentally it is found
that spirals with at least one-half turn up to 3 turns work
well, with 1.5 turns being a good number
3. The highest frequency in the spiral antenna's operating
band occurs when the innermost radius of the spiral (i.e.
where the spiral starts after the feed structure) is equal to
lambda/4 (one quarter wavelength). That is, the highest
frequency can be determined from the inner radius
21. they are commonly used on aircraft or other metallic
backed objects. As such, it is desirable to design the
antenna to be cavity-backed by some metal.
This isolates the spiral antenna from what is behind it, so
that it can be mounted on objects without worrying
about retuning the antenna.
Cavity-Backed for spiral antenna
23. Archimedean Spiral Antenna design in matlab 2016
Create and view a 2-turn Archimedean spiral antenna with a 1 mm starting radius and 40 mm outer radius.
Anten1= spiralArchimedean('Turns',2, 'InnerRadius',1e-3, 'OuterRadius',40e-3);
show(Anten1) ;
24. Applications of spiral antenna
➢ Spiral antennas are widely used in the defense industry for
sensing applications, where very wideband antennas that do
not take up much space are needed. Other applications of
spiral antennas include GPS, where it is advantageous to have
RHCP (right hand circularly polarized) antennas.
➢ Spiral arrays systems are typically used in high gain applications
such as high data rate satellite and terrestrial communication
networks also in ultra-wideband (UWB) communication
technology
➢ Spiral antenna arrays are used in military aircraft in the 1-18 GHz
range
➢ A spiral antenna transmits EM waves having a circular
polarization
➢ Spiral antennas are useful for microwave direction-finding
26. The built-in Identification Friend
or Foe (IFF) warning system
spiral antenna designed for a wide variety of aircraft applications
27. Conclusion
advantages and disadvantage
Spiral antenna: spiral antennas have wideband frequency
On the negative side, these types of antennas are difficult
to fee geometric form
spiral radiation patterns are nearly constant with frequency
Transmitter and receiver should be have same polarization
To increase the efficiency of the spiral antenna
28. 1. Antenna theory ‘http://www.antenna-theory.com’
2. Antenna magus ‘http://www.antennamagus.com.’
3. Planar Millimeter-Wave Antennas: A Comparative Study Kamil PÍTRA,
Zbyněk RAIDA Dept. of Radio Electronics, Brno University of
Technology, Purkyňova 118,
4. http://www.microwavejournal.com/articles/926-spiral-antennas-for-
broadband-applications
5. Spiral Antenna Backed by Conducting Plane Reflector , Hisumatsu
Nakano member IEEE
6. Spiral Antenna Over EBG Reflector
http://www.remcom.com/examples/spiral-antenna-over-ebg-
reflector.html
References
29. More references for more
information
1. Transmission line analysis of the Archimedean spiral
antenna in free space . ResearchGate
2. A NOVEL COMPACT ARCHIMEDEAN SPIRAL
ANTENNA WITH GAP-LOADING Progress In Electromagnetics Research
Letters, Vol. 3, 169–177, 2008
3. Analysis of Archimedean Spiral Antenna
4. ANALYSIS OF T HE EQUIANGULAR SPIRAL ANTENNA. A T he sis
Presented to The Academic Faculty -by -Michael McFadden
