UNIVERSITAT POLITÈCNICA DE CATALUNYA PONTIFICIA UNIVERSIDAD CATÓLICA DEL PERÚ CENTRE TECNOLÒGIC DE TELECOMUNICACIONS DE CATALUNYA Projecte Fi de Carrera Enginyeria de Telecomunicació DESIGN OF A CIRCULARLY POLARIZED PATCH ANTENNA FOR SATELLITE MOBILE COMMUNICATIONS IN L-BAND by Gustavo Adolfo Sotelo Bazán A thesis submitted in partial fulfillment for the degree of Engineer in the Escola Tècnica Superior d'Enginyeria de Telecomunicacions de Barcelona Departament de Teoria del Senyal i Comunicacions December 2010 1 Name : Gustavo Adolfo Sotelo Bazán. Thesis Title : Desing of a Circularly Polarized Patch Antenna for Satellite Communications in L-Band Department of Signal Theory and Communications Polytechnic University of Cataluña. Thesis Advisor : Apostolos Georgiadis. Academic Year : 2010 Abstract This project provides a detailed study of the Design of a Circularly Polarized Patch Antenna for Satellite Communications in L-band for it use on communication-navigation services such as INMARSA'T and GNSS systems. The designs were done with simulating software Advance Design System-ADS, which provides fairly reliable simulations and useful data in designing these kinds of antennas. For the construction of the antennas it has been used microstrip antenna technology, because it has been demonstrated that it is suitable for these applications due to their many advantages such as low profile and weight, easy integration with printed circuits. The antennas are etched on a RT/Duroid with dielectric substrate of 3.38 with the height of 20mil. Simulated and experimental results of several designs of the antenna are presented. 2 Agradecimientos A mi padre Gustavo y a mi madre Judith, quienes me enseñaron el valor de la educación; a mis hermanas Yudy e Sofía, por su comprensión y alegría y que a pesar de la distancia siempre estuvieron presentes. Gracias a ellos por sus oraciones, palabras de aliento, continuo apoyo y su inquebrantable fe en mí, estoy profundamente en deuda con ellos. A mi asesor, Apóstolos Georgiadis, por darme la oportunidad de realizar este proyecto de fin de carrera, así como también por sus sugerencias oportunas, orientación y estímulo; sin su apoyo constante ésta tesis no habría sido posible de realizar. Gracias Doc! A Selva Via y Ana Collado, por su gran ayuda, paciencia e incondicional apoyo en el desarrollo de los aspectos técnicos del proyecto. A los amigos ganados a lo largo de la carrera por sus valiosas sugerencias, palabras de aliento y ayuda durante esta etapa universitaria; pero sobre todo, a aquellos amigos con los que hemos compartido los “ires y venires” en el transcurso de esta enriquecedora estancia en Barcelona, con los cuales he compartido casa, viajes, cumpleaños e incontables horas de estudio. Por último, a todos y cada uno que estuvo directa o indirectamente implicado en la finalización con éxito de este proyecto. A todos ellos Muchas Gracias! Gustavo Adolfo Sotelo Bazán Diciembre 2010 3 Contents  List of Figures……………………………………………………………………………………….1 List of Tables………………………………………………………………………………………..4 1  INTRODUCTION ...........................................................................................................6   1.1  Motivation ...............................................................................................................6   1.1.1  GNSS ..............................................................................................................6   1.1.2  BGAN ............................................................................................................1 1  1.2  Objectives .............................................................................................................1 4  1.3  Organization of the Thesis ................................................................................... 14  1.4  References ...........................................................................................................1 5  2  ANTENNA’S PARAMETERS AND DEFINITIONS ...................................................... 16  2.1  Introduction ...........................................................................................................1 6  2.2  Radiation Pattern ..................................................................................................1 6  2.3  Parameters of the radiation pattern ......................................................................1 8  2.3.1  Major lobe or main beam. ............................................................................. 18  2.3.2  Minor lobe. ....................................................................................................1 8  2.3.3  Side lobe. ......................................................................................................1 8  2.3.4  Back lobe. .....................................................................................................1 8  2.4  Radiation Power Density ...................................................................................... 19  2.5  Radiation Intensity ................................................................................................2 0  2.6  Beamwidth ............................................................................................................2 0  2.7  Directivity .............................................................................................................. 21  2.8  Antenna Efficiency ................................................................................................2 2  2.9  Gain ......................................................................................................................2 2  2.10  Bandwidth .............................................................................................................2 3  2.11  Polarization ...........................................................................................................2 3  2.11.1  Linear Polarization ........................................................................................2 4  2.11.2  Circular Polarization ......................................................................................2 4  2.11.3  Elliptical Polarization .....................................................................................2 5  2.12  Input Impedance ...................................................................................................2 6  2.13  Matching ...............................................................................................................2 7  4 2.14  References ...........................................................................................................2 9  3  MICROSTRIP ANTENNA ............................................................................................3 0  3.1  Introduction ...........................................................................................................3 0  3.2  Features of the Microstrip Antenna ...................................................................... 30  3.3  Advantages and Disadvantages ........................................................................... 32  3.3.1  Advantages ...................................................................................................3 2  3.3.2  Disadvantages ..............................................................................................3 3  3.4  Methods of Analysis .............................................................................................3 3  3.5  Excitation Techniques of Microstrip Antennas ..................................................... 34  3.5.1  Coaxial or Probe Feed .................................................................................. 34  3.5.2  Microstrip line feed ........................................................................................3 5  3.5.3  Proximity Coupling ........................................................................................ 36  3.5.4  Aperture Coupled Feed ................................................................................. 37  3.6  Circularly Polarized Microstrip Antennas .............................................................. 38  3.6.1  Dual-orthogonal feed circularly polarized microstrip antennas. .................... 39  3.6.2  Singly Fed Circularly Polarized Microstrip Antennas .................................... 41  3.7  References ...........................................................................................................4 5  4  MICROSTRIP PATCH ANTENNA DESIGN AND RESULTS ...................................... 46  4.1  Introduction ...........................................................................................................4 6  4.2  Design Specifications ...........................................................................................4 6  4.3  Designs of Antennas. ...........................................................................................4 7  4.3.1  Design of antennas with one feed. ................................................................ 47  4.3.2  Design of antennas using two feeds. ............................................................ 85  4.4  References. ........................................................................................................1 01  5  CONCLUSIONS AND FUTURE WORK .................................................................... 102  6  APPENDIX ................................................................................................................ 105  6.1  Parametric Analysis of Design III ....................................................................... 105  6.1.1  Length of the impedance transformer (l) ..................................................... 106  6.1.2  Width of the impedance transformer (w) ..................................................... 108  6.1.3  Outer Radius (Rext) ....................................................................................1 10  6.1.4  Inner Radius (Rint) ......................................................................................1 12  6.1.5  Stub Length(ls) ............................................................................................ 114  6.1.6  Inner Stub ....................................................................................................1 16  5 6.1.7  Outer Stub ...................................................................................................1 20  6.2  Parametric Analysis of Design IV ....................................................................... 124  6.2.1  Outer Radius (Rext) ....................................................................................1 24  6.2.2  Inner Radius (Rint) ......................................................................................1 26  6.2.3  Length of arms (dArm) ................................................................................1 28  6.2.4  Width of arms (wArm) ................................................................................. 130  6.2.5  Radius of Slot (Rslot) ..................................................................................1 32  6.2.6  Width of Slot (Wslot) ...................................................................................1 34  6.2.7  Distance (d) .................................................................................................1 36  6.2.8  Lenght (l) .....................................................................................................1 38  6.3  Design of the Quadrature (90 º) Hybrid .............................................................. 140  6 List of Figures Figure 1.1 Shows Inmarsat's expectations of coverage. .................................................... 12  Figure 1.2 Shows a diagram of a complete BGAN system. ................................................ 13  Figure 2.1 Omnidirectional antenna pattern [2-4] ...............................................................1 7  Figure 2.2 Illustrates the radiation pattern in cartesian coordinates [2-2] .......................... 17  Figure 2.3 Illustrates the radiation pattern in polar coordinates [2-2] .................................. 18  Figure 2.4 Shows the linear plot of power pattern and its associated lobes and beamwidths [2-4]..................................................................................................................................... 19  Figure 2.5 Illustrates the HPBW and FNBW for a pattern in linear scale [2-4]. .................. 21  Figure 2.6 Illustrates the three types of polarization [2-5]. ..................................................2 6  Figure 2.7 Equivalent circuit for a receiving antenna. ......................................................... 28  Figure 3.1 Shows the top and side views of a rectangular microstrip antenna [3-3]. ......... 31  Figure 3.2 Shows other shapes of microstrip antennas [3-3]. ............................................ 31  Figure 3.3 Coaxial or Probe Feed [3-3] .............................................................................. 35  Figure 3.4 Microstrip line feed [3-3] .................................................................................... 36  Figure 3.5 Proximity coupling for underneath the patch [3-2] ............................................. 37  Figure 3.6 Aperture coupled microstrip rectangular antenna [3-3]. .................................... 38  Figure 3.7 Dual feed in a circular microstrip antenna [3-3]. ................................................ 39  Figure 3.8 Geometry of a Branch-Line Coupler. [3-5] ......................................................... 40  Figure 3.9 Aperture and phase of orthogonal modes in single point feed circularly polarized microstrip patch [3-1] .......................................................................................................... 42  Figure 3.10 Arrangement of elements for two test arrays [3-1] .......................................... 43  Figure 3.11 Measured axial ratio vs Frequency [3-1] ......................................................... 44  Figure 3.12 Measured V.S.W.R vs Frequency [3-1] ........................................................... 44  Figure 4.1 Side view of the antenna.[4-1] ........................................................................... 48  Figure 4.2 Top view of the antenna. [4-1] ........................................................................... 48  Figure 4.3 Shows the tags that identify one by one the parts of the antenna. .................... 49  Figure 4.4 Simulated return loss for antenna design I-1. .................................................... 51  Figure 4.5 Simulated Smith Chart plot for this antenna design I-1. .................................... 51  Figure 4.6 Shows the Axial Ratio for each frequency inside the impedance bandwidth. ... 52  Figure 4.7 Simulated return loss for antenna design I-2. .................................................... 54  Figure 4.8 Simulated Smith Chart plot for antenna design I-2 ............................................ 54  Figure 4.9 Shows the Axial Ratio for each frequency inside the impedance bandwidth. ... 56  Figure 4.10 Shows the structure of the antenna. [4-2] ........................................................ 57  Figure 4.11 Shows the tool used to transfer the reference of the port. ............................... 59  Figure 4.12 Shows the simulation results for the case when the reference of the port has been moved. ....................................................................................................................... 60  Figure 4.13 Simulated return loss for antenna design II-1. ................................................. 61  Figure 4.14 Simulated Smith Chart plot for antenna design II-1. ........................................ 61  Figure 4.15 Shows the Axial Ratio for each frequency inside the impedance bandwidth .. 63  Figure 4.16 Simulated return loss for the antenna design II-2. ........................................... 64  Figure 4.17 Simulated Smith Chart plot for the antenna design II-2. .................................. 65  Figure 4.18 Shows the Axial Ratio for each frequency inside the impedance bandwidth .. 66  1 Figure 4.19 Shows the top view of the antenna. ................................................................. 68  Figure 4.20 Shows the labels of the parts art of the antenna. ............................................ 69  Figure 4.21 Simulated return loss for antenna design III. ................................................... 71  Figure 4.22 Simulated Smith Chart plot for antenna design III. .......................................... 72  Figure 4.23 Shows the Axial Ratio for each frequency inside the impedance bandwidth .. 73  Figure 4.24 Shows the gain values vs frequency. .............................................................. 74  Figure 4.25 Radiation Pattern for a planar cut of 0 degrees at 1.6 GHz. ............................ 74  Figure 4.26 Radiation Pattern for a planar cut of 90 degrees at 1.6 GHz. .......................... 75  Figure 4.27 Shows the LPKF Protolaser-S machine. ......................................................... 76  Figure 4.28 Shows the Bottom substrate with the contours marked by the LPKF Protolaser-S machine .........................................................................................................7 7  Figure 4.29 Shows the top substrate with the unwanted cupper removed. ........................ 78  Figure 4.30 Shows the antenna assembled ....................................................................... 79  Figure 4.31 Shows the comparison between the simulated and measured results. ........... 80  Figure 4.32 Shows the scheme for measuring ................................................................... 81  Figure 4.33 Measured Received power at broadside rotating the antenna under test relative to the transmit antenna. The ripple corresponds to the Axial Ratio ....................... 81  Figure 4.34 Shows the plot comparing simulated vs measured axial ratio values. ............ 83  Figure 4.35 Radiation pattern measured for antenna design III ......................................... 84  Figure 4.36 Shows the top view of the antenna. ................................................................. 85  Figure 4.37 Shows the labels of the parts art of the antenna. ............................................ 86  Figure 4.38 Simulated return loss. ......................................................................................8 8  Figure 4.39 Simulated Smith Chart plot. .............................................................................8 8  Figure 4.40 Shows the Axial Ratio for each frequency inside the simulated bandwidth ..... 89  Figure 4.41 Shows the gain and directivity values vs frequency ........................................ 91  Figure 4.42 Radiation Pattern for a planar cut of 0 degrees at 1.6 GHz. ............................ 91  Figure 4.43 Radiation Pattern for a planar cut of 90 degrees at 1.6 GHz ........................... 92  Figure 4.44 Shows the lower substrate with the contours marked by the LPKF Protolaser-S machine .............................................................................................................................. 93  Figure 4.45 Shows the Top view of the upper substrate with the contours marked by the LPKF Protolaser-S machine ...............................................................................................9 4  Figure 4.46 Shows the upper and lower substrates with the unwanted cupper removed. . 96  Figure 4.47 Shows the antenna assembled ....................................................................... 98  Figure 4.48 Shows the comparison between the simulated and measured results. ........... 98  Figure 4.49 Measured Received power at broadside rotating the antenna under test relative to the transmit antenna. The ripple corresponds to the Axial Ratio ....................... 99  Figure 4.50 Shows the plot comparing simulated vs measured axial ratio values. .......... 101  Figure 6.1 Design IV of antenna with its labels ................................................................. 105  Figure 6.2 Axial Ratio values for each frequency. ............................................................ 106  Figure 6.3 Shows the variation of the input impedance in the Smith Chart. ..................... 107  Figure 6.4 Axial Ratio values for each frequency. ............................................................ 108  Figure 6.5 Shows the variation of the input impedance in the Smith Chart. ..................... 109  Figure 6.6 Axial Ratio values for each frequency. ............................................................ 110  Figure 6.7 Shows the variation of the input impedance in the Smith Chart. ..................... 111  2 Figure 6.8 Axial Ratio values for each frequency. ............................................................ 112  Figure 6.9 Shows the variation of the input impedance in the Smith Chart. ..................... 113  Figure 6.10 Axial Ratio values for each frequency. .......................................................... 115  Figure 6.11 Shows the variation of the input impedance in the Smith Chart. ................... 115  Figure 6.12 Axial Ratio values for each frequency. .......................................................... 116  Figure 6.13 Shows the variation of the input impedance in the Smith Chart. ................... 117  Figure 6.14 Axial Ratio values for each frequency. .......................................................... 118  Figure 6.15 Shows the variation of the input impedance in the Smith Chart. ................... 119  Figure 6.16 Axial Ratio values for each frequency. ......................................................... 121  Figure 6.17 Shows the variation of the input impedance in the Smith Chart. ................... 121  Figure 6.18 Axial Ratio values for each frequency. .......................................................... 122  Figure 6.19 Shows the variation of the input impedance in the Smith Chart. ................... 123  Figure 6.20 Design IV of antenna with its labels ............................................................... 124  Figure 6.21 Axial Ratio values for each frequency. .......................................................... 125  Figure 6.22 Shows the variation of the input impedance in the Smith Chart. ................... 126  Figure 6.23 Axial Ratio values for each frequency. .......................................................... 127  Figure 6.24 Shows the variation of the input impedance in the Smith Chart. ................... 127  Figure 6.25 Axial Ratio values for each frequency. .......................................................... 128  Figure 6.26 Shows the variation of the input impedance in the Smith Chart. ................... 129  Figure 6.27 Axial Ratio values for each frequency. .......................................................... 130  Figure 6.28 Shows the variation of the input impedance in the Smith Chart. ................... 131  Figure 6.29 Axial Ratio values for each frequency. .......................................................... 132  Figure 6.30 Shows the variation of the input impedance in the Smith Chart. ................... 133  Figure 6.31 Axial Ratio values for each frequency. .......................................................... 134  Figure 6.32 Shows the variation of the input impedance in the Smith Chart. ................... 135  Figure 6.33 Axial Ratio values for each frequency. .......................................................... 136  Figure 6.34 Shows the variation of the input impedance in the Smith Chart. ................... 137  Figure 6.35 Axial Ratio values for each frequency. .......................................................... 138  Figure 6.36 Shows the variation of the input impedance in the Smith Chart. ................... 139  Figure 6.37 Layout of a Quadrature Hybrid in microstrip technology [6-1] ....................... 140  Figure 6.38 Model of the Hybrid used in ADS ................................................................. 141  Figure 6.39 Line Calc analysis to obtain the parameters of Z0 ........................................ 142  Figure 6.40 Line Calc analysis to obtain the parameters of Z ......................................... 143  1 Figure 6.41 Shows the numbering employed for the ports. .............................................. 144  Figure 6.42 S parameter magnitudes versus frequency for the hybrid ............................. 144  Figure 6.43 Shows the phase for port 4 and 3 at the frequency of 1.59GHz .................... 145  3 List of Tables Table 1-1 Shows the frequency bands of GNSS systems .................................................. 11  Table 1-2 Specifications of the antenna for the receiver equipment.[1-5] .......................... 13  Table 1-3 Shows the antenna’s specifications. ................................................................... 14  Table 3-1 General characteristics of Power Divider Networks. [3-6] .................................. 41  Table 4-1 Shows materials used and their parameters. ..................................................... 47  Table 4-2 Shows the values of the parts of the antenna. ................................................... 50  Table 4-3 Shows the axial ratio for each frequency inside the impedance bandwidth. ...... 52  Table 4-4 Shows the values of the parts of the antenna. ................................................... 53  Table 4-5 Shows the axial ratio for each frequency inside the impedance bandwidth. ...... 55  Table 4-6 Summary and comparison of both designs. ....................................................... 56  Table 4-7 Shows the dimensions of the antenna. ............................................................... 59  Table 4-8 Shows the axial ratio for each frequency inside the impedance bandwidth ....... 62  Table 4-9 Shows the dimensions of the antenna. ............................................................... 63  Table 4-10 Shows the axial ratio for each frequency inside the impedance bandwidth ..... 66  Table 4-11Summary and comparison of both designs. ...................................................... 67  Table 4-12 Shows the dimensions of the antenna. ............................................................. 71  Table 4-13 Shows the axial ratio for each frequency inside the impedance bandwidth ..... 72  Table 4-14 Shows the gain for each simulated frequency. ................................................. 73  Table 4-15 Shows a summary of the comparison. ............................................................. 80  Table 4-16 Simulated vs Measured axial ratio values. ....................................................... 82  Table 4-17 Shows the dimensions of the antenna. ............................................................. 87  Table 4-18 Shows the axial ratio for each frequency inside the impedance bandwidth ..... 89  Table 4-19 Shows the gain and directivity for each simulated frequency. .......................... 90  Table 4-20 Shows a summary of the comparison. ............................................................. 99  Table 4-21 Simulated vs Measured axial ratio values. ..................................................... 100  Table 5-1 Main features of the antennas simulated and built. .......................................... 102  Table 5-2 Specifications of the antenna design ................................................................ 102  Table 6-1 Axial ratio for each frequency and with different values of “l”. .......................... 106  Table 6-2 Axial ratio for each frequency and with different values of “w”. ........................ 108  Table 6-3 Axial ratio for each frequency and with different values of “Rext”. ................... 110  Table 6-4 Axial ratio for each frequency and with different values of “Rint”. .................... 112  Table 6-5 Axial ratio for each frequency and with different values of “ls”. ........................ 114  Table 6-6 Axial ratio for each frequency and with different values of “WStubInt”. ............ 116  Table 6-7 Axial ratio for each frequency and with different values of “LStubInt”. ............. 118  Table 6-8 Axial ratio for each frequency and with different values of “WStubExt”. .......... 120  Table 6-9 Axial ratio for each frequency and with different values of “LStubExt”. ............ 122  Table 6-10 Axial ratio for each frequency and with different values of “Rext”. ................. 125  Table 6-11 Axial ratio for each frequency and with different values of “Rint”. .................. 126  Table 6-12 Axial ratio for each frequency and with different values of “dArm”. ................ 128  Table 6-13 Axial ratio for each frequency and with different values of “wArm”. ................ 130  Table 6-14 Axial ratio for each frequency and with different values of “Rslot”. ................. 132  4