Yagi Antenna Design for Animal Tracking Applications

Yagi Antenna Design for Yagi Antenna Design for Animal Tracking Animal Tracking

ApplicationsApplicationsMinh Phan, Andrew Price, Denny TuMinh Phan, Andrew Price, Denny Tu

University of Illinois at Urbana-ChampaignUniversity of Illinois at Urbana-ChampaignDepartment of Electrical EngineeringDepartment of Electrical Engineering

Senior Design, ECE345Senior Design, ECE345May 2, 2003May 2, 2003

Motivation for ProjectMotivation for Project

The current method used to track tagged The current method used to track tagged animals requires scientists to manually animals requires scientists to manually drive around with portable antennas drive around with portable antennas tracking the particular animal(s) they are tracking the particular animal(s) they are interested in. This method is very time interested in. This method is very time consuming and produces small amounts of consuming and produces small amounts of data. In order to facilitate an automatic data. In order to facilitate an automatic tracking system, antennas to receive the tracking system, antennas to receive the signals from the tags must be designed, signals from the tags must be designed, built and tested. built and tested.

Whole System OverviewWhole System Overview

Antenna 1

Antenna 6

RF switch matrix

AmplifiersFiltersSignal Processing

Data Display

(this project only involves the dashed part)

ObjectivesObjectives

Design a yagi antenna using simulation Design a yagi antenna using simulation software.software.

Build the antenna according to designed Build the antenna according to designed specifications.specifications.

Test antenna and verify it performs as Test antenna and verify it performs as expected.expected.

Design an RF switch matrix to switch 6 Design an RF switch matrix to switch 6 antenna feed lines to 1 or 2 amplifiers in antenna feed lines to 1 or 2 amplifiers in the down conversion module.the down conversion module.

The Yagi AntennaThe Yagi Antenna

Invented in the 1920s by Hidetsugu Yagi Invented in the 1920s by Hidetsugu Yagi and Shintaro Uda, two Japanese university and Shintaro Uda, two Japanese university professorsprofessors

A type of multielement arrayA type of multielement array

Components of a YagiComponents of a Yagi

Center boomCenter boom• Can be metallic, but requires correction to Can be metallic, but requires correction to

elementselements


One driven elementOne driven element• Connected to sourceConnected to source• Only active elementOnly active element


One reflectorOne reflector• Positioned behind the driven elementPositioned behind the driven element• Reflects radiation in desired directionReflects radiation in desired direction


N ≥ 0 directorsN ≥ 0 directors• Placed in front of driven elementPlaced in front of driven element• Directs radiation in desired directionDirects radiation in desired direction• Focuses radiation patternFocuses radiation pattern


Matching deviceMatching device• Matches impedance Matches impedance

of antenna to a of antenna to a desired valuedesired value

• T matchT match Matches impedance Matches impedance

of antenna to 50of antenna to 50ΩΩ Balanced matching Balanced matching

devicedevice• Reduces pattern Reduces pattern

distortiondistortion


BalunBalun• Connects BALanced antenna to Connects BALanced antenna to

UNbalanced coaxUNbalanced coax Prevents common-mode currents Prevents common-mode currents

on the outer surface of the outer on the outer surface of the outer conductor of the coax feed which conductor of the coax feed which can affect the pattern and other can affect the pattern and other propertiesproperties

• Can also perform an Can also perform an impedance transformationimpedance transformation


1:1 balun1:1 balun

How a Yagi WorksHow a Yagi Works

Driven element radiatesDriven element radiates Radiation induces currents in Radiation induces currents in

reflector and directorsreflector and directors These currents in turn re-radiateThese currents in turn re-radiate Adjusting the length of elements, Adjusting the length of elements,

their diameters and relative positions their diameters and relative positions along the boom adjusts the radiated along the boom adjusts the radiated fieldsfields


The previously mentioned The previously mentioned parameters are adjusted in such a parameters are adjusted in such a way as to make the fields way as to make the fields constructively interfere in one constructively interfere in one direction, and destructively interfere direction, and destructively interfere in the opposite directionin the opposite direction

This creates the typical directional This creates the typical directional radiation patternradiation pattern


Design RequirementsDesign Requirements

Half-power beam width ≈ 60°Half-power beam width ≈ 60°• In order to ensure adequate coverage of In order to ensure adequate coverage of

areas between antennasareas between antennas As large a gain as possibleAs large a gain as possible As large a front-to-back ratio as As large a front-to-back ratio as

possiblepossible Connect to a 50Ω coax cableConnect to a 50Ω coax cable

Yagi DesignYagi Design

Used Quickyagi to design antennaUsed Quickyagi to design antenna

Used Yagicad to determine matching Used Yagicad to determine matching parametersparameters


E plane fieldE plane field


H plane fieldH plane field

Yagi DesignYagi Design A conducting boom A conducting boom

will be used to build will be used to build the antenna, so a the antenna, so a correction to the correction to the lengths of the lengths of the elements is required elements is required to prevent pattern to prevent pattern distortionsdistortions

Boom diameter = Boom diameter = 1.25” ≈ .032 1.25” ≈ .032 λλ

Correction ≈ Correction ≈ 29%*1.25” ≈ 9mm29%*1.25” ≈ 9mm

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Yagi ConstructionYagi Construction

MaterialsMaterials• BoomBoom

6’ long aluminum tube6’ long aluminum tube 1.25” outer diameter1.25” outer diameter

• ElementsElements 3/16” diameter aluminum (copper for driven 3/16” diameter aluminum (copper for driven

element) rodselement) rods

• Plastic insulators and push-nut retaining Plastic insulators and push-nut retaining rings to attach elements to boomrings to attach elements to boom

Yagi ConstructionYagi Construction

Holes in boom drilled by computer Holes in boom drilled by computer controlled machine in the ECE controlled machine in the ECE machine shopmachine shop

Elements cut using band saw in ECE Elements cut using band saw in ECE machine shopmachine shop

T-match bars and balun soldered onT-match bars and balun soldered on

Antenna-Network Analyzer (NA)Antenna-Network Analyzer (NA)

First step One port (port1) First step One port (port1) calibrate by use SOLT calibrate by use SOLT (short, open, load, and (short, open, load, and through) standard kit. So through) standard kit. So port 1 will be connect to port 1 will be connect to Yagi antenna.Yagi antenna.

From NA we should see at From NA we should see at corrected calibration by corrected calibration by display Smitch chart such display Smitch chart such as Open, short, and load as Open, short, and load located as where it should located as where it should be.be.

The frequency range from The frequency range from 100mhz to 1Ghz100mhz to 1Ghz

Example show standard kitExample show standard kit

Using a coax cable Using a coax cable 50 ohms hookup 50 ohms hookup with a adapter then with a adapter then we connected each we connected each of components as of components as disired from disired from stanadard kit short, stanadard kit short, open, and load. Let open, and load. Let take a look at the take a look at the LoadLoad

Connect through NAConnect through NA

Port1 have been done calibrate then Port1 have been done calibrate then connect yagi antenna at this time we connect yagi antenna at this time we will try get it match 50 ohms.will try get it match 50 ohms.

Port2 connect monopole with coax Port2 connect monopole with coax cable 50 ohmscable 50 ohms

Monopole Antenna - PurposeMonopole Antenna - Purpose

Not in our original plan.Not in our original plan. For testing, needed constant For testing, needed constant

transmitter for yagi antenna to transmitter for yagi antenna to receive signal.receive signal.

Difficult to find/use natural Difficult to find/use natural transmitters operating at 302MHz transmitters operating at 302MHz (band of our yagi is narrow).(band of our yagi is narrow).

Can use easily in lab.Can use easily in lab.

Monopole Antenna - TransmitterMonopole Antenna - Transmitter Extended center Extended center

conductor of a coax cable conductor of a coax cable of length of length λλ/4 ≈ 25cm to /4 ≈ 25cm to transmit at 302 MHztransmit at 302 MHz

Ground plane: aluminum Ground plane: aluminum foil covered cardboard foil covered cardboard basebase

Ground plane: 50cm x Ground plane: 50cm x 50cm, equidistant from 50cm, equidistant from center conductor on all center conductor on all sidessides

CopperCopper tape to connect tape to connect outer conductor of coaxial outer conductor of coaxial cable to ground planecable to ground plane

Testing – Impedance BackgroundTesting – Impedance Background

Ideal: 50 ohms real, 0 ohms reactanceIdeal: 50 ohms real, 0 ohms reactance Impedance Matching is what the calibration Impedance Matching is what the calibration

was needed for.was needed for. Theory T Match: use 0.2m copper wire, arm Theory T Match: use 0.2m copper wire, arm

length 2.7cm, spacing 2.1cm, capacitance length 2.7cm, spacing 2.1cm, capacitance 16pF16pF

Testing – Impedance ProcedureTesting – Impedance Procedure 1. Connect antenna 1. Connect antenna

port1port1 2. Direct antenna 2. Direct antenna

facing out open lab facing out open lab window in order to window in order to minimize reflection minimize reflection (accuracy)(accuracy)

3. Read impedance 3. Read impedance using Smith Chart and using Smith Chart and marker at 302MHzmarker at 302MHz

4. Adjust connectors, 4. Adjust connectors, test different lengthstest different lengths

Testing – Impedance Testing – Impedance Procedure2Procedure2

5. Couldn’t achieve close to 5. Couldn’t achieve close to desired impedance. desired impedance.

6. Hypothesis: Balun may be at 6. Hypothesis: Balun may be at fault, so remove it.fault, so remove it.

7. More testing, still no positive 7. More testing, still no positive results.results.

8. Get additional wire, 8. Get additional wire, according to theoretical according to theoretical predictions.predictions.

9. Silver wire very difficult to 9. Silver wire very difficult to solder.solder.

10. Test T-Match and Gamma-10. Test T-Match and Gamma-Match, still not desired results.Match, still not desired results.

11. Replace with 14mm copper 11. Replace with 14mm copper wire, bend, test.wire, bend, test.

12. Discover wiring incorrect.12. Discover wiring incorrect. 13. Correct wiring and attach 13. Correct wiring and attach

balun once more because balun once more because needed to match currents.needed to match currents.

Testing – Impedance Testing – Impedance Procedure3Procedure3

14. More testing and 14. More testing and adjusting, Gamma-Match, adjusting, Gamma-Match, T-MatchT-Match

15. Recheck and redo the 15. Recheck and redo the solder connectionssolder connections

16. Adjust height, distance, 16. Adjust height, distance, angle, etc.angle, etc.

Finally, achieve results Finally, achieve results close to ideal goal:close to ideal goal:• 51.1 real, 2.3 51.1 real, 2.3

reactance, 97.5 % get reactance, 97.5 % get throughthrough

• 47.5 real, -13.5 47.5 real, -13.5 reactance, 86 % get reactance, 86 % get throughthrough

Testing – Impedance SWRTesting – Impedance SWR

Standing Wave Standing Wave Ratio near 1 Ratio near 1 demonstrates demonstrates matching working matching working well (very little well (very little reflected):reflected):

SWR Formula: SWR Formula: |r| = |r| = (SWR-1)/(SWR+1)(SWR-1)/(SWR+1)

Antenna – Power Reflection (Log Scale)Antenna – Power Reflection (Log Scale)

Spike at 302 MHz – Spike at 302 MHz – desireddesired

Spike larger than -Spike larger than -10 dB10 dB

No other major No other major spikesspikes

Works according to Works according to designdesign

Testing – Radiation TestsTesting – Radiation Tests Calibration not essential, normalizeCalibration not essential, normalize H-plane is horizontal, E-plane verticalH-plane is horizontal, E-plane vertical Direction of poles have to alignDirection of poles have to align Minimum distance 1-2m between Minimum distance 1-2m between

transmitter and receivertransmitter and receiver Radiation pattern ideally symmetricRadiation pattern ideally symmetric 2 Procedures:2 Procedures:

• Keep Yagi receiver stationary and rotate Keep Yagi receiver stationary and rotate monopole transmitter around it at set degree monopole transmitter around it at set degree intervalsintervals

• Keep monopole stationary and turn the Yagi in Keep monopole stationary and turn the Yagi in a circlea circle

Testing – Radiation Procedure1Testing – Radiation Procedure1 1. Connect monopole to port21. Connect monopole to port2 2. Keep Yagi stationary on top 2. Keep Yagi stationary on top

of 2 chair backs – step back of 2 chair backs – step back so human body doesn’t so human body doesn’t adversely affect results.adversely affect results.

3. Hold monopole as far away 3. Hold monopole as far away as possible.as possible.

4. Starting at 0 degrees, take 4. Starting at 0 degrees, take measurements and proceed in measurements and proceed in 10 degree increments up to 10 degree increments up to 180 degrees.180 degrees.

5. Keep monopole level with 5. Keep monopole level with Yagi.Yagi.

6. Plot points in Matlab and 6. Plot points in Matlab and compare with ideal results compare with ideal results obtained from simulation.obtained from simulation.

7. Repeat several times for 7. Repeat several times for accuracy.accuracy.

Testing – Radiation Procedure2Testing – Radiation Procedure2 1. Locate monopole 1. Locate monopole

antenna next to window antenna next to window (minimize reflection) and (minimize reflection) and keep stationary.keep stationary.

2. Set Yagi on chair backs 2. Set Yagi on chair backs facing the monopole.facing the monopole.

3. Keep monopole and Yagi 3. Keep monopole and Yagi level.level.

4. Take measurements 4. Take measurements starting at 0 degrees and starting at 0 degrees and going to 180 degrees.going to 180 degrees.

5. After each 5. After each measurement, turn Yagi measurement, turn Yagi antenna 10 degrees, make antenna 10 degrees, make stationary, step away.stationary, step away.

6. Repeat several times.6. Repeat several times. 7. Analyze results.7. Analyze results.

Testing – Radiation Procedure3Testing – Radiation Procedure3

Test if height of monopole relative to Test if height of monopole relative to Yagi affects results:Yagi affects results:• Conclusion: not significantly.Conclusion: not significantly.

Test if distance of monopole relative Test if distance of monopole relative to Yagi affects results:to Yagi affects results:• Conclusion: beyond 1 meter, it seems to Conclusion: beyond 1 meter, it seems to

stay the same.stay the same.

Testing – Results Power SpectrumTesting – Results Power Spectrum

Spike at 302 MHz, Spike at 302 MHz, as designed.as designed.

No other No other comparable spikes.comparable spikes.

Worked as Worked as expectedexpected

Testing – Results Radiation PatternTesting – Results Radiation Pattern

Similar to ideal results simulated using Similar to ideal results simulated using computer softwarecomputer software

Front to Back Ratio: -30.6 dB/-39.1 dBFront to Back Ratio: -30.6 dB/-39.1 dB Graph shows front half of radiation pattern:Graph shows front half of radiation pattern:

Testing – Results Radiation Pattern Testing – Results Radiation Pattern 22

0 degree to 180 degree sweep.0 degree to 180 degree sweep. Somewhat different from expected results but general Somewhat different from expected results but general

shape similar.shape similar. Discrepancies attributed to non-ideal testing Discrepancies attributed to non-ideal testing

conditions and reflections.conditions and reflections.

Obstacles and Challenges 1Obstacles and Challenges 1 Graduate Student Advisor departedGraduate Student Advisor departed

• The person we worked most with and assisted us with The person we worked most with and assisted us with direction and guidance.direction and guidance.

Switch MatrixSwitch Matrix• Part of original plan – take input from 6 antennas, Part of original plan – take input from 6 antennas,

switching between all 6 within 15ms so as to not miss switching between all 6 within 15ms so as to not miss any data. Produce 1 output that computer program any data. Produce 1 output that computer program others working on “decodes” to find location of animals.others working on “decodes” to find location of animals.

• Many fruitless hours searching and planning.Many fruitless hours searching and planning.• Ideas that wouldn’t work, didn’t match the specific Ideas that wouldn’t work, didn’t match the specific

project specifications and functions.project specifications and functions.• Professor George Swenson said too difficult for us to do Professor George Swenson said too difficult for us to do

in our meeting with him.in our meeting with him.

Obstacles and Challenges 2Obstacles and Challenges 2

Suitable Testing Environment:Suitable Testing Environment:• Ideal: isolated, open area without conflicting Ideal: isolated, open area without conflicting

signals but with necessary equipment and signals but with necessary equipment and accessibility.accessibility.

• Antenna testing lab on top floor of Everitt Antenna testing lab on top floor of Everitt unsuitable for our antenna bandwidth.unsuitable for our antenna bandwidth.

• ECE345 Lab turned out to be most viable ECE345 Lab turned out to be most viable option but many people working around us = option but many people working around us = disruptions, conflicting signals, reflections, disruptions, conflicting signals, reflections, human interference.human interference.

Obstacles and Challenges 3Obstacles and Challenges 3 CalibrationCalibration

• Only one calibration set found and needed Only one calibration set found and needed someone to calibrate for us since owner of someone to calibrate for us since owner of calibration set didn’t want to leave it with us.calibration set didn’t want to leave it with us.

• Unable to save calibration so another group Unable to save calibration so another group using or turning off network analyzer means using or turning off network analyzer means we need to calibrate again.we need to calibrate again.

• Owner of calibration set not always available Owner of calibration set not always available and we couldn’t proceed without it.and we couldn’t proceed without it.

Obstacles and Challenges 4Obstacles and Challenges 4 Impedance MatchingImpedance Matching

• Very unstable, the slightest touch makes a big change.Very unstable, the slightest touch makes a big change.• Varies a great deal – sometimes one location gives a Varies a great deal – sometimes one location gives a

value, another time the same location gives a totally value, another time the same location gives a totally different value.different value.

• Human touch/proximity affects results significantly.Human touch/proximity affects results significantly. MiscellaneousMiscellaneous

• Faulty cablesFaulty cables• Find sufficient cables and connectors to be able to test Find sufficient cables and connectors to be able to test

using a single network analyzer while maintaining using a single network analyzer while maintaining sufficient distance between Yagi and monopole.sufficient distance between Yagi and monopole.

AcknowledgementsAcknowledgements

ECE Professor BernhardECE Professor Bernhard ECE Graduate student Brian HertingECE Graduate student Brian Herting Professor Larkin of the INHSProfessor Larkin of the INHS 345 TA Chirantan Mukhopadhyay345 TA Chirantan Mukhopadhyay ECE Professor George SwensonECE Professor George Swenson

Documents

Yagi Antenna Design for Animal Tracking Applications