LiU-ITN-TEK-A--17/044--SE Phased array antenna element evaluation Jacob Samuelsson 2017-08-25 Department of Science and Technology Institutionen för teknik och naturvetenskap Linköping University Linköpings universitet nedewS ,gnipökrroN 47 106-ES 47 ,gnipökrroN nedewS 106 47 gnipökrroN LiU-ITN-TEK-A--17/044--SE Phased array antenna element evaluation Examensarbete utfört i Elektroteknik vid Tekniska högskolan vid Linköpings universitet Jacob Samuelsson Handledare Adriana Serban Examinator Qin-Zhong Ye Norrköping 2017-08-25 Upphovsrätt Detta dokument hålls tillgängligt på Internet – eller dess framtida ersättare – under en längre tid från publiceringsdatum under förutsättning att inga extra- ordinära omständigheter uppstår. Tillgång till dokumentet innebär tillstånd för var och en att läsa, ladda ner, skriva ut enstaka kopior för enskilt bruk och att använda det oförändrat för ickekommersiell forskning och för undervisning. Överföring av upphovsrätten vid en senare tidpunkt kan inte upphäva detta tillstånd. All annan användning av dokumentet kräver upphovsmannens medgivande. För att garantera äktheten, säkerheten och tillgängligheten finns det lösningar av teknisk och administrativ art. Upphovsmannens ideella rätt innefattar rätt att bli nämnd som upphovsman i den omfattning som god sed kräver vid användning av dokumentet på ovan beskrivna sätt samt skydd mot att dokumentet ändras eller presenteras i sådan form eller i sådant sammanhang som är kränkande för upphovsmannens litterära eller konstnärliga anseende eller egenart. För ytterligare information om Linköping University Electronic Press se förlagets hemsida http://www.ep.liu.se/ Copyright The publishers will keep this document online on the Internet - or its possible replacement - for a considerable time from the date of publication barring exceptional circumstances. The online availability of the document implies a permanent permission for anyone to read, to download, to print out single copies for your own use and to use it unchanged for any non-commercial research and educational purpose. Subsequent transfers of copyright cannot revoke this permission. All other uses of the document are conditional on the consent of the copyright owner. The publisher has taken technical and administrative measures to assure authenticity, security and accessibility. According to intellectual property law the author has the right to be mentioned when his/her work is accessed as described above and to be protected against infringement. For additional information about the Linköping University Electronic Press and its procedures for publication and for assurance of document integrity, please refer to its WWW home page: http://www.ep.liu.se/ © Jacob Samuelsson i Abstract This thesis evaluates two array antenna elements for large phased array antennas. The two antenna concepts are a surface mounted notch element and a PIFA (Planar Inverted F Antenna). The antennas have been simulated at S-band in Ansys HFSS as a unit cell in an infinite array environment. Thereafter, a finite 7 x 7 element array of the two concepts was simulated. A corresponding 49 element array, using the notch element, was built and measured upon. Embedded element patterns and S-matrix parameters have been measured. From this result, full array antenna patterns as well as active reflection coefficients have been calculated. The measurements show very good performance for large scan angles and a wide frequency range. ii Acknowledgement First I would like to express my gratitude for the help and support from SAAB AB during this thesis. Special thanks to my supervisor Bengt Svensson and Martin Nilsson from SAAB AB in Göteborg. I would like to thank my supervisor Adriana Serban and examiner Qin-Zhong Ye at the Department of Science and Technology (ITN) at Linköping University for their help and support under the thesis. Finally, I would like to thank Ansys for providing a license for HFSS under this thesis. iii Table of Contents Abstract i Acknowledgement ii Table of Contents iii List of Figures v List of tables vii 1 Introduction .................................. 1 1.1 Purpose ................................. 1 1.2 Problem Formulations ......................... 2 1.3 Specification of Requirements ..................... 2 1.4 Delimitations .............................. 2 1.5 Outline ................................. 2 2 Theory ..................................... 4 2.1 Fundamentals of Radar ......................... 4 2.2 Fundamentals of Antennas ....................... 6 2.2.1 Radiation Pattern ......................... 6 2.2.2 Directivity and Gain ....................... 9 2.2.3 Band- and Beamwidth ..................... 10 2.2.4 Polarization ........................... 11 2.2.5 Scattering Parameters ..................... 12 2.2.6 Amplitude tapering ....................... 13 2.2.7 Beam Scanning ......................... 14 2.2.8 Active Reflection Coefficient ................. 15 2.2.9 Embedded Element Pattern .................. 16 2.3 Planar Inverted F Antenna ...................... 16 2.4 Surface mount notch element .................... 19 3 Method ................................... 22 3.1 Simulation ............................... 22 3.1.1 Model .............................. 23 3.1.2 Boundaries ........................... 27 3.1.3 Excitations ........................... 28 3.1.4 Analysis ............................. 29 3.1.5 Optimetrics ........................... 30 3.1.6 Field Pattern .......................... 30 3.2 Measurements ............................. 31 3.2.1 Measurements of Scattering Parameters ............ 31 3.2.2 Measurements of Antenna Gain ................ 32 4 Planar Inverted F Antenna ......................... 34 iv Table of Contents 4.1 Parameter sweep ........................... 34 4.2 Infinite Array ............................. 36 4.3 Finite Array .............................. 37 5 Surface Mount Notch Antenna ....................... 38 5.1 Parameter sweep ........................... 38 5.2 Infinite Array ............................. 42 5.3 Finite Array .............................. 44 5.3.1 Scattering parameter ...................... 44 5.3.2 Antenna Gain ......................... 46 6 Discussion .................................. 49 6.1 Results ................................. 49 6.2 Simulations .............................. 50 6.3 Measurements ............................. 50 7 Conclusion ................................. 52 Bibliography ............................... 53 v List of Figures 1 Main and sidelobes in an antenna pattern, with illustration of the beamwidth in the lobe [2]. ......................... 7 2 Reference coordinate system [2]. ..................... 8 3 Half Power Beamwidth and Full Null Beamwidth of an antenna pattern [2]. ................................ 10 4 Illustration of polarization of electromagnetic wave a) rotation of traveling wave b) elliptical polarization at Z=0 [2]. ........... 11 5 Arbitrary N-port microwave network [5]. ................ 12 6 Illustration of electrically beam scanning or beam steering of a uniform array [6]. ............................. 15 7 General PIFA element dimensions, the feed point indicates the connection of a SMA coaxial contact, [11]. ............... 17 8 The PIFA element corresponding to the (19) where the dimensions are shown [16]. .............................. 18 9 Vivaldi antenna design with the characteristic tapered slot. The black, is the feeding line [21]. ...................... 20 10 Project manager in HFSS. ........................ 22 11 PIFA element model in HFSS, single polarized. The model is the same for the initial and final model. ................... 23 12 Finite array of 49 PIFA elements. .................... 24 13 Surface mount notch element with a resonance cavity single polarized where a) is the final model and b) is the initial model. .... 25 14 Finite array model of the Surface mount notch element. The array consists of 49 elements. ......................... 26 15 Master and slave boundaries of a unit cell. ............... 27 16 Wave port exciatiation of the coaxial feed port. ............. 28 17 Floquet port excitation of a unit cell. .................. 29 18 Convergence of the HFSS analysis. ................... 30 19 Measurement setup for S-parameters. .................. 31 20 The Array positioned in the anechoic chamber a) array fixed on the moving arm b) close up picture. ..................... 32 21 The mounting of coaxial cables, a) on the antenna b) on the switch. .. 33 22 Magnitudes of reflection for parameter sweep of a) length parameter L and b) width of the radiation patch W. ................ 35 23 Magnitudes of reflection for parameter sweep of a) height parameter h and b) the feed position fp. ...................... 36 24 Magnitudes of reflection for beam steering of the infinite array in q = 0°, 30° and 60° in a) E-plane or j =0° and b) H-plane or j =90° .. 36 25 Radiation pattern for PIFA in realized gain (dBi) at 3 GHz with -30 dB Taylor tapering. Beam steering in a) E-plane and b) H-plane for q = 0° (blue), 30° (green) and 60° (red). ................. 37 vi List of Figures 26 Magnitudes of reflection for parameter sweep of a) length parameter L and b) thickness parameter t. ..................... 39 27 Magnitudes of reflection for parameter sweep of a) the channel height to the cavity Lo and b) the slot line width parameter Ws .... 40 28 Magnitudes of reflection for parameter sweep of a) the cavity offset from the slot line centre Coff and b) variation of the cavity height Lc.