3D Printed Horn Antenna for Ultra Wideband Applications

135 Pages·2017·17.57 MB·English

3D Printed Horn Antenna for Ultra
Wideband Applications
By Vegard Midtbøen
Thesis submitted for the degree of
Master of science in Electronics and computer
science, Microelectronics
60 credits
Department of Informatics
Faculty of mathematics and natural sciences
UNIVERSITY OF OSLO
Spring 2017

3D Printed Horn Antenna for
Ultra Wideband Applications
By Vegard Midtbøen
©2017ByVegardMidtbøen
3DPrintedHornAntennaforUltraWidebandApplications
http://www.duo.uio.no/
Printed: Reprosentralen,UniversityofOslo
Abstract
This thesis was initiated by the University of Oslo at the Department of Informat-
ics. The field of study regarding snow analysis, characterization and imaging of
snowlayers, hasbeenanongoingstudy-fieldattheDepartmentofGeophysicsfor
some years. The transverse collaboration project, Land-ATmosphere Interactions
inColdEnvironment(LATICE)seeksnewadvancedinstrumentsforcharacterizing
the impact of climate changes to the snow. In this thesis, 3D printed high gain,
ultra-wideband antennas for snow-penetrating radar applications has been simu-
latedandmanufactured.
A custom build stepped ridge horn antenna was found to be best suited regard-
ing large bandwidth and high gain that covers the entire band. Two antennas have
been constructed and characterized for a gain between 10 dBi to 15 dBi covering
the range between 2.3 GHz to 6.1 GHz. The antennas are 3D printed in low cost
polylactic acid (PLA) and coated with conductive copper spray. The measured
half-powerbeamwidthforthefirstprintedantennais26 intheE-planeand26 in
◦ ◦
the H-plane. For the second printed antenna, the half-power beamwidth is 24 in
◦
theE-planeand28 intheH-plane. Measuredpeakdirectivityis12.6dBiand12
◦
dBi,andthefront-to-backratiois22dBand24dBforthefirstandsecondantenna,
respectively. Inaddition,anewtechniqueforfeeding3Dprintedwaveguidestruc-
turesarepresented. Theworkonthisfeedingtechniquehasbeensubmittedtothe
IEEE MTT-S International Microwave Workshop Series on Advanced Materials
andProcesses(IMWS-AMP)conferenceinSeptember20-22,2017(AppendixA).
The antennas have been tested together with the Novelda X2 Ventricorder mod-
uleatthesnowlabattheDepartmentofInformatics,andoutdoormeasurementsat
FinseAlpineResearchCenter,Norway. Promisingresultshasbeenachievedfrom
these measurements. The radar is able to detect different layers of pressed wood
withameasuredpermittivityof1.89. Resultsfromtheoutdoormeasurementshas
beenshownintheendofthethesis,butnotverifiedduetolimitedtime.
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Contents
1 Introduction 1
1.1 SurfacePenetratingRadar . . . . . . . . . . . . . . . . . . . . . 1
1.2 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Motivationandgoals . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Background 7
2.1 FundamentalsofRADAR . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 Targetdetection . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.2 Dielectricpropertiesofamaterial . . . . . . . . . . . . . 8
2.1.3 Resolution . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.4 Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Usingradarforsnowimaging . . . . . . . . . . . . . . . . . . . . 18
2.2.1 Snowavalanches . . . . . . . . . . . . . . . . . . . . . . 19
2.2.2 Surfacepenetratingradars . . . . . . . . . . . . . . . . . 20
2.3 DirectionalUWBAntennasforsnowimaging . . . . . . . . . . . 24
2.3.1 Reflectorantennas . . . . . . . . . . . . . . . . . . . . . 24
2.3.2 Microstriparrayantennas . . . . . . . . . . . . . . . . . 26
2.3.3 Hornantennas . . . . . . . . . . . . . . . . . . . . . . . 28
2.4 Hornantennaparameters . . . . . . . . . . . . . . . . . . . . . . 31
2.4.1 Waveguidedesignparameters . . . . . . . . . . . . . . . 31
2.4.2 Feedingtechniquesforrectangularwaveguides . . . . . . 35
2.4.3 Horndesignparameters . . . . . . . . . . . . . . . . . . 35
2.4.4 Summaryofhornantennaparameters . . . . . . . . . . . 36
2.5 Systemoverview . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.5.1 Antennaparameters . . . . . . . . . . . . . . . . . . . . 37
2.5.2 Practicalusage . . . . . . . . . . . . . . . . . . . . . . . 37
2.5.3 Designspecificationoverview . . . . . . . . . . . . . . . 38
3 Designandanalysis 39
3.1 Designmethod . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.2 Designofpyramidalhornantenna . . . . . . . . . . . . . . . . . 40
3.2.1 Designingawaveguideforrectangularhorn . . . . . . . . 40
3.2.2 Feedingarectangularwaveguide . . . . . . . . . . . . . . 41
3.2.3 Simulationofrectangularwaveguide . . . . . . . . . . . . 42
3.2.4 Designofhornaperture . . . . . . . . . . . . . . . . . . 43
3.2.5 Simulationofrectangularhornantenna . . . . . . . . . . 44
3.2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . 47
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CONTENTS iv
3.3 Designoftapereddoubleridgedhornantenna . . . . . . . . . . . 49
3.3.1 Designofridgedwaveguide . . . . . . . . . . . . . . . . 49
3.3.2 Feedingtheridgedwaveguide . . . . . . . . . . . . . . . 49
3.3.3 Simulationofridgedwaveguide . . . . . . . . . . . . . . 50
3.3.4 Design of double ridged waveguide for a new cut-off
frequency . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.3.5 Designoftaperedridgedhornaperture . . . . . . . . . . 53
3.3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.4 Anewmethodforfeedingplasticwaveguides . . . . . . . . . . . 62
3.4.1 Microstriptransmissionlinefeed . . . . . . . . . . . . . . 62
3.4.2 Simulationofmicrostriptransmissionlinefeed . . . . . . 64
3.4.3 Evaluationthemicrostripfeed . . . . . . . . . . . . . . . 65
3.5 Designofsteppedridgehornantenna . . . . . . . . . . . . . . . 68
3.5.1 Designofsteppedridgewaveguide. . . . . . . . . . . . . 68
3.5.2 Simulationofsteppedridgewaveguide . . . . . . . . . . 69
3.5.3 Designofsteppedridgehornantenna . . . . . . . . . . . 71
3.5.4 Simulation of stepped ridge horn antenna with microstrip
transmissionlinefeed. . . . . . . . . . . . . . . . . . . . 72
3.5.5 Summaryofsteppedridgehornantenna . . . . . . . . . . 73
3.6 3Dprintedantennas . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.6.1 Challengesby3Dprintingantennas . . . . . . . . . . . . 74
3.6.2 3Dprintedsteppedridgehornantenna . . . . . . . . . . . 74
4 Measurementsandresults 77
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.2 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.3 Evaluationoftheprintedwaveguide . . . . . . . . . . . . . . . . 79
4.3.1 Measuredresultsforthefirstprintedwaveguide . . . . . . 79
4.3.2 SummaryoftheprintedwaveguidewithPCBfeed . . . . 81
4.4 Printedsteppedridgehornantenna . . . . . . . . . . . . . . . . . 83
4.4.1 Measuredreflectioncoefficient . . . . . . . . . . . . . . . 83
4.4.2 Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.4.3 Polarization . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.4.4 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.5 Radarmeasurements . . . . . . . . . . . . . . . . . . . . . . . . 88
4.5.1 Snowlabmeasurements . . . . . . . . . . . . . . . . . . 88
4.5.2 Fieldmeasurements . . . . . . . . . . . . . . . . . . . . 90
4.6 Summaryofallresults . . . . . . . . . . . . . . . . . . . . . . . 94
5 Discussion 95
5.1 Issuesregarding3Dprintingantennas . . . . . . . . . . . . . . . 95
5.1.1 3Dprinting . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.1.2 Coppercoating . . . . . . . . . . . . . . . . . . . . . . . 95
5.2 InterfacebetweenPCBandwaveguide . . . . . . . . . . . . . . . 97
5.3 Suggestionsforfurtherwork . . . . . . . . . . . . . . . . . . . . 98
5.3.1 Newwaveguidedesign . . . . . . . . . . . . . . . . . . . 98
5.3.2 PCBfeed . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.3.3 OnesinglePCBforacompleteradarsystem . . . . . . . . 99
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5.4 Alternativeradarapplications . . . . . . . . . . . . . . . . . . . . 100
6 Conclusion 101
Appendices 109
A Paper 111
B Machinedrawings 115
CONTENTS vi