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Onur Hamza Karabey

Electronic Beam Steeringand Polarization Agile PlanarAntennas in Liquid CrystalTechnology

Doctoral Thesis accepted byTechnische Universität Darmstadt, Germany

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AuthorDr. Onur Hamza KarabeyInstitut für Mikrowellentechnik

und Photonik (IMP), FachgebietElektro- und Informationstechnik (ETiT)

Technische Universität DarmstadtDarmstadtGermany

SupervisorProf. Dr.-Ing. Rolf JakobyInstitut für Mikrowellentechnik

und Photonik (IMP), FachgebietElektro- und Informationstechnik (ETiT)

Technische Universität DarmstadtDarmstadtGermany

ISSN 2190-5053 ISSN 2190-5061 (electronic)ISBN 978-3-319-01423-4 ISBN 978-3-319-01424-1 (eBook)DOI 10.1007/978-3-319-01424-1Springer Cham Heidelberg New York Dordrecht London

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Parts of this thesis have been published in the following documents:

Journals

O. H. Karabey, S. Bildik, S. Bausch, S. Strunck, A. Gaebler, and R. Jakoby,‘‘Continuously polarization agile antenna by using liquid crystal based tunablevariable delay lines,’’ IEEE Transactions on Antennas and Propagation, vol. 61,no. 1, jan., 2013.

O. H. Karabey, S. Gaebler, A.and Strunck, and R. Jakoby, ‘‘A 2-D electronicallysteered phased-array antenna with 2x2 elements in lc display technology,’’ IEEETransactions on Microwave Theory and Techniques, vol. 60, pp. 1297–1306,2012.

O. H. Karabey, S. Bildik, S. Strunck, A. Gaebler, and R. Jakoby, ‘‘Continuouslypolarisation reconfigurable antenna element by using liquid crystal based tunablecoupled line,’’ Electronics Letters, vol. 48, pp. 141–143, 2012.

O. H. Karabey, M. Maasch, and R. Jakoby, ‘‘Stable satellite link by liquid crystalbased phased array antennas,’’ ATZelektronik, Springer Vieweg, vol. 04,pp. 46–50, 2012.

O. H. Karabey, M. Maasch, and R. Jakoby, ‘‘Stabile Satellitenverbindung durchFluessigkristallbasierte Phasengesteuerte Gruppenantennen,’’ ATZelektronik,Springer Vieweg, vol. 04, pp. 300-306, 2012.

International Conferences and Workshops

O. H. Karabey, S. Bausch, S. Bildik, S. Strunck, A. Gaebler, and R. Jakoby,‘‘Design and application of a liquid crystal varactor based tunable coupled line forpolarization agile antennas,’’ in Microwave Conference (EuMC), 2012 European,2012.

O. H. Karabey, F. Goelden, S. Gaebler, A.and Strunck, and R. Jakoby, ‘‘Tunableloaded line phase shifters for microwave applications,’’ in Microwave SymposiumDigest (MTT), 2011 IEEE MTT-S International, 2011.

O. H. Karabey, B. Saavedra, C. Fritzsch, S. Strunck, A. Gaebler, and R. Jakoby,‘‘Methods for improving the tuning efficiency of liquid crystal based tunable phaseshifters,’’ in Microwave Integrated Circuits Conference (EuMIC), 2011 European,2011.

O. H. Karabey, S. Bildik, C. Fritzsch, S. Strunck, A. Gaebler, R. Jakoby, and A.Manabe, ‘‘Liquid crystal based reconfigurable antenna arrays,’’ in 32nd ESAAntenna Workshop on Antennas for Space Applications, 2010.

O. H. Karabey, F. Goelden, A. Gaebler, and R. Jakoby, ‘‘Precise broadbandmicrowave material characterization of liquids,’’ in Microwave Conference(EuMC), 2010 European, 2010.

O. H. Karabey, Y. Zheng, A. Gaebler, F. Goelden, and R. Jakoby, ‘‘A synthesistechnique for multiband tunable impedance matching networks with optimizeddomain,’’ in German Microwave Conference, 2009, 2009.

Patent

O. H. Karabey, F. Goelden, A. Manabe, R. Jakoby: ‘‘Electronically steerableplanar phased array antenna’’,European Patent: EP 2 575 211 A1,International Patent (PCT): WO2013045267A1.

For my estimable elder, E.A.,and for his precious family.His warm smile and kind words,I will always remember.

Supervisor’s Foreword

It is a great pleasure to introduce Dr. Onur Hamza Karabey’s thesis work, acceptedfor publication within Springer Theses and awarded with a prize for an outstandingoriginal work. Dr. Karabey joint my research group for Microwave Engineeringafter finishing the ‘‘Information and Communication Engineering (ICE) Interna-tional Master Program’’ at Technische Universität Darmstadt in September 2008.He started his doctoral study with a three-year scholarship of the DFG-Gradu-iertenkolleg 1037 ‘‘Tunable Integrated Components in Microwave Technologyand Optics’’ and completed it with an oral defense on 5th April 2013.

Since about a decade, researchers around the world are searching for appro-priate enabling technologies to realize devices and components for advancedwireless systems at radio and microwave frequencies, having smart hardwarefunctionalities, either for frequency tuning and adaptive impedance/powermatching or electronic polarization-tuning and beam-steering. One promisingapproach, as presented in this thesis, is the microwave Liquid Crystal (LC)technology developed by my group at TU Darmstadt together with the liquidcrystal division of the Merck Company in Darmstadt, where high-performance LCmaterials have been specifically synthesized for microwaves. This microwave LCmaterials feature low dielectric loss above 10 GHz as well as continuous andquasi-powerless tunability in terms of relative permittivity. By adapting the well-established LC display technology beyond optics, Dr. Karabey investigated in theframe of his thesis, different novel concepts for low-cost, low-profile (flat andcompact) electronic beam-steering, and polarization-agile antennas. His compre-hensive study focusses on 360� variable delay-line phase shifters in LC technol-ogy, as key components. His systematic analysis includes theory, design,techniques, and the proof-of-concept of multi-layer structures in various planarwaveguide topologies with controllable characteristics by using thin LC cavities aswell as planar loaded-line approaches, using LC varactors as tuning elements. Forthe very first time, Dr. Karabey successfully demonstrate the full capability ofthese novel approaches and the LC technology by integrating LC-based delay-linephase shifters in spiral geometry beneath each antenna element with physical sizeof about 0.55 k0 9 0.55 k0 (k0 is the wavelength in air) of a full 2D-beam-steeringphased array and two new polarization-agile antennas. All these reconfigurable

ix

antenna demonstrators operate at Ku-/Ka-band and consist of 2 9 2 microstrippatch antenna elements with an overall thickness of 1.5 mm, only.

Dr. Karabey’s thesis includes significant original scientific contributions rep-resenting considerable advancement in this field of electronically reconfigurableantennas based on LC technology, which he published as first author in topjournals and international well-recognized conferences. Moreover, with his inno-vative ideas proposed in this thesis, Dr. Karabey is the main inventor of two patentapplications and won the ‘‘Ideenwettbewerb 2011’’ of Technische UniversitätDarmstadt.

Utilizing automated manufacturing techniques analogy to LC display technol-ogy, Dr. Karabey’s scientific work enables to fabricate low profile, low cost, high-gain beam-steering, and polarization-agile antennas, able to adjust dynamically itsbeam and polarization by electronics. This will have some potential for futureportable and mobile applications, e.g., for airplanes connecting satellites or forterminals integrated into the body (cover, rooftop) of laptops, automobiles, ships,or boats, receiving broadcast or onboard Internet access if the antenna can elec-tronically connected to a satellite constantly.

Darmstadt, 4 June 2013 Rolf Jakoby

x Supervisor’s Foreword

Acknowledgments

This dissertation presents my research performed as Ph.D. candidate in theInstitute for Microwave Engineering and Optics at Technische UniversitätDarmstadt. I would like to start the dissertation by acknowledging to people, whocontributed to my research intangibly.

In the first place, I would like to thank my supervisor Prof. Dr.-Ing. RolfJakoby. Doubtless, this work could not be performed without his valuable guid-ance and trust. He always encouraged to take responsibilities and provided aflexible working environment, which also developed my personal skills. In thesecond place, I would like to thank Prof. Dr. Ozlem Aydin Civi. During myundergraduate studies, she taught me in antennas and now, she takes part in as aco-examiner in my Ph.D., which is dedicated for tunable antennas.

I am indebted to my former colleagues Dr. Stefan Mueller and especially to Dr.Felix Goelden for inspiring me for the topics studied in this work. These topicswere, of course, advanced with fruitful discussion with my colleagues AlexanderGaebler, Sebastian Strunck, Saygin Bildik, Matthias Maasch, Christian Mandel,Carsten Fritzsch, Matthias Hansli, Dr. Yuliang Zheng, Dr. Christian Damm, andDr. Holger Maune. My workload is reduced considerably with helps of WenjuanHu and Ananto Eka Prasetiadi with productive teamworking. This work became areality with practical supports of Peter Kiesslich and Andreas Semrad in theworkshop and Karin Boye in the clean room. I am also thankful to ArshadMehmood for reviewing my dissertation.

Furthermore, my special thanks go to• Atsutaka Manabe and his colleagues in Merck KGaA, Darmstadt because of

the trustworthy cooperation and providing liquid crystal samples,• Prof. Dr. Philippe Ferrari and Assoc. Prof. Dr. Anne-Laure Franc from the

IMEPLAHC Microelectronics, Electromagnetism and Photonic Institute,Grenoble, with whom the liquid crystal technology is innovatively applied forslow wave phase shifters at W-band frequencies,

• Prof. Dr. Wolfgang Haase and Dr. Artsiom Lapanik from the Eduard-Zintl-Institut fuer Anorganische and Physikalische Chemie at Technische Uni-versität Darmstadt for helping me to get insight into liquid crystal chemistry,

• Dr. Serhend Arvas from the Sonnet Software Inc., North Syracus for teachingme to use simulation tools efficiently, regardless of the distance.

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Last but not least, I would like to thank my relatives, parents, and parents inlove for supporting and motivating me in uneasy and long Ph.D. journey. Specialthanks go to my darling wife and four month old son. They supported me morallyand shared my difficulties in any case.

Neu-Isenburg, 23 January 2013 Onur Hamza Karabey

xii Acknowledgments

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Electronic Beam Steering Phased Arrays . . . . . . . . . . . . . . . . . 21.3 Polarization Agile Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 Structure of this Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Liquid Crystal Material for Microwave Applications. . . . . . . . . . . 92.1 Fundamentals of Liquid Crystal Materials . . . . . . . . . . . . . . . . 9

2.1.1 Response of Liquid Crystal Moleculesin Electromagnetic Fields. . . . . . . . . . . . . . . . . . . . . . . 12

2.1.2 Alignment Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . 152.2 Fundamentals of Tunable Inverted Microstrip Lines . . . . . . . . . 19

2.2.1 Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.2.2 Working Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3 Microwave Material Characterization. . . . . . . . . . . . . . . . . . . . . . 273.1 Broadband Microwave Characterization of Liquid Crystals. . . . . 27

3.1.1 Coaxial Line Characterization Method. . . . . . . . . . . . . . 283.1.2 Parameter Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . 293.1.3 Effects of Inner Conductor Bending . . . . . . . . . . . . . . . 313.1.4 Measurement Setup and Results . . . . . . . . . . . . . . . . . . 35

3.2 Microwave Characterization of Glasses . . . . . . . . . . . . . . . . . . 393.2.1 Split-cylinder-cavity Method . . . . . . . . . . . . . . . . . . . . 393.2.2 On-wafer Characterization Method . . . . . . . . . . . . . . . . 41

3.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

4 2D Electronic Beam Steering Phased Array . . . . . . . . . . . . . . . . . 474.1 Liquid Crystal Based Variable Delay Line Topologies . . . . . . . . 48

4.1.1 Transmission Line Variable Delay Lines . . . . . . . . . . . . 494.1.2 Periodically Loaded Variable Delay Lines . . . . . . . . . . . 51

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4.2 Realization and Measurements of Variable Delay Lines . . . . . . . 584.2.1 Meandered Inverted Microstrip Line . . . . . . . . . . . . . . . 584.2.2 LC Varactor Loaded Coplanar Waveguide . . . . . . . . . . . 604.2.3 LC Varactor Loaded Slotline . . . . . . . . . . . . . . . . . . . . 664.2.4 LC Varactor Loaded Microstrip Line. . . . . . . . . . . . . . . 694.2.5 Comparison of Different Topologies . . . . . . . . . . . . . . . 77

4.3 Electronic Beam Steering Phased Array . . . . . . . . . . . . . . . . . . 854.3.1 Antenna Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854.3.2 Design and Verification . . . . . . . . . . . . . . . . . . . . . . . . 874.3.3 Measurement Results. . . . . . . . . . . . . . . . . . . . . . . . . . 93

4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

5 Polarization Agile Antennas in LC Technology . . . . . . . . . . . . . . . 1075.1 Tunable Coupled Line Based Polarization Agile Antenna. . . . . . 108

5.1.1 Antenna Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085.1.2 Tunable Coupled Line Analyzes . . . . . . . . . . . . . . . . . . 1095.1.3 Realization and Measurement Results . . . . . . . . . . . . . . 114

5.2 Variable Delay Line Based Polarization Agile Antenna . . . . . . . 1185.2.1 Antenna Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1185.2.2 Design and Verification . . . . . . . . . . . . . . . . . . . . . . . . 1195.2.3 Measurement Results and Discussions . . . . . . . . . . . . . . 124

5.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

6 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Appendix A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

xiv Contents

Symbols and Abbreviations

ap Electric polarisabilityve Electric susceptibilityvm Magnetic susceptibilityD/b Differential phase shift‘physical Physical length of a devicegs Tuning efficiency of a liquid crystal devicegLC Material tunabilitygVDL Variable delay-line efficiencyC Reflection coefficientscLC Rotational viscosity of the liquid crystal moleculesk Magnetic polarizabilityl0 Permeability of free space, 4p 9 10-7 N/A2

x Angular frequency

ðÞ$ Tensorial matrix of a given property in ()

k Parallel alignment with respect to an electromagnetic field\ Perpendicular alignment with respect to an electromagnetic field/‘ Electrical length/b Phase shift/‘;NTL Electrical length of a not tunable liner Conductivitytan d Material (dielectric) loss tangentsLC Material efficiencyIL Insertion lossN Molecular number densityHm Main beam directionc Complex propagation constantl

rComplex relative permeability

er Complex relative permittivityeeff Complex effective relative permittivitySij Scattering parameters

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e0 Permittivity of free space, 8.85 x 10-12 F/mer Realitive permittivityn! Director

D! Dielectric displacement

E! Electrical field

H! Magnetic field

P! Macroscopic polarization

p! Induced dipole momentc0 Speed of light in vacuum & 3 x 108 m/sf0 Operating frequencyhLC Height of the liquid crystal layerKii, Elastic constant for the splay (i = 1), twist (i = 2) and bend (i = 3)

deformationsS Order parameterton, toff Response timesTc Clearing temperature pointTm Melting temperature pointVSat Saturation voltageVth Threshold voltageVb Bias voltageZLine Characteristic impedance of a transmission lineZNTL Characteristic impedance of a not tunable lineZB Bloch impedanceAu Gold metalIMSL Inverted microstrip lineLC Liquid crystalMUT Material under testNi-Cr Nickel-chromium alloyNRW Nicolson-Ross-WeirNTL Not tunable lineRF Radio frequencySLL Side lobe levelUE Unit elementUV Ultraviolet lightVAR VaractorVDL Variable delay line

xvi Symbols and Abbreviations