Jun 24, 2015
RADIATION & PROPOGATION
-Broadband AntennasBroadband Antennas
AJAL.A.J Assistant Professor –Dept of ECE,
UNIVERSAL ENGINEERING COLLEGE, THRISSUR- 680123 - INDIAMob: 8907305642
MAIL: [email protected]
Broadband AntennasBroadband Antennas
OverviewOverview
Typical antennas are designed for a specific Typical antennas are designed for a specific narrow band of operationnarrow band of operation
Broadband antennas are designed to operate Broadband antennas are designed to operate effectively over a wide range of frequencieseffectively over a wide range of frequencies Public two-way-radio VHF covers 130-174MhzPublic two-way-radio VHF covers 130-174Mhz Public two-way-radio UHF 406-512MhzPublic two-way-radio UHF 406-512Mhz The challenge is to create an antenna which can The challenge is to create an antenna which can
operate in both the VHF and UHF bandsoperate in both the VHF and UHF bands
BandwidthBandwidth
%100
C
LUP f
ffB
L
UR f
fB
2LU
C
fff
Definition for center frequency:Definition for center frequency:
Bandwidth can be expressed as a percentage of the Bandwidth can be expressed as a percentage of the center frequency or as a ratiocenter frequency or as a ratio
The percentage is commonly used for small bandwidth The percentage is commonly used for small bandwidth antennas:antennas:
The ratio is commonly used for large bandwidth antennas:The ratio is commonly used for large bandwidth antennas:
6
Broad Spectrum of Types
HelicalHelical
Log PeriodicLog Periodic
BiconicalBiconical
SleeveSleeve
SpiralSpiral
Narrow Band AntennasNarrow Band Antennas
Circularly Polarized Linearly PolarizedCircularly Polarized Linearly Polarized
Dipole
Feed Horns
Yagi-UdaUniform Helical
Broad Band AntennasBroad Band Antennas
Circularly Polarized Linearly PolarizedCircularly Polarized Linearly Polarized
Tapered Helical Tapered Yagi-Uda
Spiral Planar
Array of narrow band antennas
PolarizationPolarization
helical antennas have circular polarization
Parameters VariedParameters Varied
Conductor material
Size of conductor
Cont. Parameters VariedCont. Parameters Varied
SMA connector Feeding pointSMA connector Feeding point
TuningTuning
Biconical AntennaBiconical Antenna
Types of BiconicalTypes of Biconical Infinite BiconicalInfinite Biconical Finite BiconicalFinite Biconical Discone Discone
Log Periodic AntennaLog Periodic Antenna
The antenna is ideally suited for The antenna is ideally suited for reception of VHF/UHF point-to-reception of VHF/UHF point-to-point communication where its point communication where its directional characteristics can directional characteristics can significantly improve rejection of significantly improve rejection of interfering signals. interfering signals. In professional applications, this In professional applications, this antenna is ideally suited for EMC antenna is ideally suited for EMC pre-testing, surveillance and pre-testing, surveillance and monitoring. monitoring. The antenna covers a frequency The antenna covers a frequency range of 230 to 1600 MHz (a range of 230 to 1600 MHz (a much wider frequency range can much wider frequency range can be received with reduced gain). be received with reduced gain). http://www.winradio.com/home/http://www.winradio.com/home/ax31b.htmax31b.htm
Sleeve AntennaSleeve Antenna
The sleeve antenna is used The sleeve antenna is used primarily as a receiving primarily as a receiving antenna. It is a broadband, antenna. It is a broadband, vertically polarized, vertically polarized, omnidirectional antenna. Its omnidirectional antenna. Its primary uses are in broadcast, primary uses are in broadcast, ship-to-shore, and ground-to-ship-to-shore, and ground-to-air communications. Although air communications. Although originally developed for shore originally developed for shore stations, there is a modified stations, there is a modified version for shipboard use. version for shipboard use.
http://www.tpub.com/inch/http://www.tpub.com/inch/32.htm32.htm
http://www.emartin.it/it9vky/http://www.emartin.it/it9vky/Risorse/opensleeve.htmRisorse/opensleeve.htm
Spiral AntennaSpiral Antenna
The spiral antenna is used The spiral antenna is used primarily as a receiving antennaprimarily as a receiving antennaVertically polarizedVertically polarizedFrequency IndependentFrequency Independent
Designed to minimize finite lengths Designed to minimize finite lengths and maximize angular dependenceand maximize angular dependence
http://www.naapo.org/Argus/docs/990702.htm
http://www.emi.dtu.dk/research/afg/research/gpr/spiral_antenna.html
http://www.ece.uiuc.edu/pubs/antenna/slide03.html
Helical AntennaHelical Antenna
normalnormal axialaxial
Helix antennaHelix antennawas was invented by J. D. invented by J. D. KrausKraus. .
two modes of operation,two modes of operation,
Helix Antenna StoryHelix Antenna Story
Dr. John KrausDr. John Kraus
Professor of Electrical Professor of Electrical Engineering and Engineering and
Astronomy EmeritusAstronomy Emeritus
Ohio State UniversityOhio State University
Radiation PatternsRadiation Patterns
NORMAL MODE
Radiation PatternsRadiation Patterns
AXIAL MODE
Geometrical ConsiderationsGeometrical Considerations
S
D1
L
D2
Matching Network
Building the First PrototypeBuilding the First Prototype
Building the ArrayBuilding the Array
Increasing the DiameterIncreasing the Diameter
Matching NetworkKapton Tape
D1D2
CalculationsCalculations
MeasurementsMeasurements
Return LossReturn Loss
VSWRVSWR
Resonance and MatchingResonance and Matching
ReflectionReflection SWRSWR Return LossReturn Loss Smith ChartSmith Chart ImpedanceImpedance
TransmissionTransmission
GainGain
Spectrum AnalyzerSpectrum Analyzer Signal Generator
Helical AntennaHelical Antenna
DirectionalDirectional
Circularly PolarizedCircularly Polarized Polarization changes Polarization changes
with time with time
Both high gain and Both high gain and wide bandwide band
1989 ONWARDS
19891989Early Helix – 2 x 10 TurnsEarly Helix – 2 x 10 Turns
1991 1991 2 x 15 Turn 70 cm Helix 2 x 15 Turn 70 cm Helix
About 1994About 1994AO-13 AntennasAO-13 Antennas
20012001AO-40 AntennasAO-40 Antennas
2003 2003 13 and 23 cm Helix Arrays13 and 23 cm Helix Arrays
GeometryGeometry
Antenna TheoryAntenna Theory, Constantine A. Balanis, Constantine A. Balanis
D= diameter of helix
C= circumference of helix
Lo= length of one turn =
α= pitch angle =
S= spacing between turns
N= number of turns
Lw= length of helix
d= diameter of conductor
Normal ModeNormal Mode
Radiation pattern similar Radiation pattern similar to linear dipoleto linear dipole
The dimensions of the The dimensions of the helix are small compared helix are small compared to the wavelengthto the wavelength
Narrow in bandwidthNarrow in bandwidth
Radiation efficiency is Radiation efficiency is smallsmall
Rarely usedRarely used
Axial ModeAxial Mode
Circular PolarizationCircular Polarization ¾<C/¾<C/λλ<4/3<4/3 C/C/λλ=1:near optimum=1:near optimum S= S= λλ/4/4
Half-Power Beam width: 50 x 50 degreesHalf-Power Beam width: 50 x 50 degrees
Directivity:Directivity:
Typical Gain: 10dBTypical Gain: 10dB
Bandwidth: 52%Bandwidth: 52%
Frequency limit: 100MHZ to 3GHzFrequency limit: 100MHZ to 3GHz
http://www.mobile.ss.titech.ac.jp/~ken/broadband-antennas.pdfhttp://www.mobile.ss.titech.ac.jp/~ken/broadband-antennas.pdf
NSC
23
52
3
2
15SC
N
Helix ApplicationsHelix ApplicationsSpace Telemetry Applications of satellites, Space Telemetry Applications of satellites, space probes, and ballistic missilesspace probes, and ballistic missiles Signals have undergone Faraday rotationSignals have undergone Faraday rotation
Directional applicationsDirectional applications
Adaptation of Single Antenna for Adaptation of Single Antenna for Multi-band Use.Multi-band Use.
Test Equipment Set UpTest Equipment Set Up
Antenna Test RangeAntenna Test Range
Spiro-Helical AntennaSpiro-Helical Antenna
double helix gps antennadouble helix gps antenna
GPS & GLONASS
thanks for your patient listening