RADIATION & PROPOGATION

-Broadband AntennasBroadband Antennas

AJAL.A.J Assistant Professor –Dept of ECE,

UNIVERSAL ENGINEERING COLLEGE, THRISSUR- 680123 - INDIAMob: 8907305642

MAIL: ec2reach@gmail.com

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