Spiral Antenna

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
TheIEEEStandard Definitionsof
TermsforAntennas(IEEEStd145–1983)∗
definestheantennaoraerialas“means
forradiatingorreceivingradiowaves.”

4. History
In1954,EdwinTurnurstartedmessingwithadipole
antenna.Insteadofleavingthearmsstraight,he
wrappedthemaroundeachother,formingaspiral.
Thiswasthebeginningofthespiralantenna
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 Bandwidthcan 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 Bandwidthcan 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
Spiralantennasareusuallycircularlypolarized.The
spiralantenna’sradiationpatterntypicallyhasa
peakradiationdirectionperpendiculartotheplane
ofthespiral(broadsideradiation).
Thisisaverybroadbeamwidthforcircular
polarization;thisisoneofthefeaturesthatmakes
spiralantennasveryuseful.
A left-handed-CCW
circularly polarized wave
A right-handed-CW
circularly polarized wave

8. The SpiralAntenna has circular polarization over a wide beamwdith,
often for angular regions as wide as
.
TheHalf-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
Thisfigureshowtheinputimpedanceofthetwoarmsspiral
antenna isapproximatelyconstantwithvaryingthe
frequency.Researchwasdonein[5]

11. In generally Gain between : 2-8dB
Gain

12. Researchwasdonein[6]twoarmsspiralantenna
r1 = 0.3 cm ,
r 2=10 cm
8 turns, a = 0.0757 cm

13. Archimedean Spiral Antenna Log-Periodic Spiral Antenna
Type of spiral antenna

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 : Cis 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 100-150Ohm range.

17. Also it is known as equiangular spiral antenna
Wecandefinethearmsofaspiralantennausingsimplepolar
coordinatesandpolarfunctions.Thelog-periodicspiralantenna,
alsoknownastheequiangularspiralantenna,haseacharm
definedbythepolarfunction
where:
R0=constantthatcontrolstheinitial
radiusofthespiralantenna
a=parameterthatcontrolstherateat
whichthespiralantennagrowswith
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.
thehighestfrequencyinthespiralantenna’scanbedeterminedfromthe
innerradius(R0)

20. 2.NumberofTurns(N)-Thenumberofturnsofthespiral
isalsoadesignparameter.Experimentallyitisfound
thatspiralswithatleastone-halfturnupto3turnswork
well,with1.5turnsbeingagoodnumber
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.
Thisisolatesthespiralantennafromwhatisbehindit,so
thatitcanbemountedonobjectswithoutworrying
aboutretuningtheantenna.
Cavity-Backed for spiral antenna

22. Antenna Magus design web
Radiation pattern of spiral antenna with cavity

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
➢Spiralantennasarewidelyusedinthedefenseindustryfor
sensingapplications,whereverywidebandantennasthatdo
nottakeupmuchspaceareneeded.Otherapplicationsof
spiralantennasincludeGPS,whereitisadvantageoustohave
RHCP(righthandcircularlypolarized)antennas.
➢Spiralarrayssystemsaretypicallyusedinhighgainapplications
suchashighdataratesatelliteandterrestrialcommunication
networksalsoinultra-wideband (UWB)communication
technology
➢Spiralantennaarraysareusedinmilitaryaircraftinthe1-18GHz
range
➢AspiralantennatransmitsEMwaveshavingacircular
polarization
➢Spiralantennasareusefulformicrowavedirection-finding

25. Spiral Array antenna in missiles

26. Thebuilt-inIdentificationFriend
orFoe(IFF)warningsystem
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.PlanarMillimeter-WaveAntennas:AComparativeStudyKamilPÍTRA,
ZbyněkRAIDA Dept.ofRadioElectronics,BrnoUniversityof
Technology,Purkyňova118,
4.http://www.microwavejournal.com/articles/926-spiral-antennas-for-
broadband-applications
5.SpiralAntennaBackedbyConductingPlaneReflector,Hisumatsu
NakanomemberIEEE
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.TransmissionlineanalysisoftheArchimedean spiral
antennainfreespace.ResearchGate
2.A NOVEL COMPACT ARCHIMEDEAN SPIRAL
ANTENNAWITHGAP-LOADINGProgressInElectromagneticsResearch
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