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# Spiral Antenna

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### Spiral Antenna

1. 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. 2. Outlines  Introduction  History of the spiral antenna  Bandwidth of the antenna  Polarization  Gain  Type of spiral antenna  Some parameter design  Application  Conclusion
3. 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. 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. 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. 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. 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. 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. 9. The radiation pattern of the Log-Periodic Spiral Antenna is approximately given by: Directivity 3D plot of radiation pattern
10. 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]
11. 11. In generally Gain between : 2-8dB Gain
12. 12. Research was done in [6] two arms spiral antenna r1 = 0.3 cm , r 2=10 cm 8 turns, a = 0.0757 cm
13. 13. Archimedean Spiral Antenna Log-Periodic Spiral Antenna Type of spiral antenna
14. 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. 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. 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. 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. 18. Axial ratio of antenna in free space Impedance of antenna in free space
19. 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. 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. 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
22. 22. Antenna Magus design web Radiation pattern of spiral antenna with cavity
23. 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. 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
25. 25. Spiral Array antenna in missiles
26. 26. The built-in Identification Friend or Foe (IFF) warning system spiral antenna designed for a wide variety of aircraft applications
27. 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. 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. 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