Satellite Ground Station Antennas

Roland Schwerdtfeger was a Life Member of the IEEE with decades of experience in ground station design and operation, achieving global recognition as the definitive expert.Thomas A. Milligan has served as Principal Engineer for numerous advanced antenna design projects and NASA planetary probes. He is an IEEE Life Fellow and former longtime editor of the "Antenna Designer's Notebook" column in the IEEE Antenna Magazine.Robert Hoferer, PhD, has 30 years' experience in antenna feed systems and reflector antennas for satellite communication. A Senior Member of the IEEE, he has served since 2013 as co-founder and Chief Technology Officer for Spacetime Engineering.Christophe Granet, PhD, is an award-winning antenna engineer with over 30 years' experience, and founder of Lyrebird Antenna Research Ltd. He is a Senior Member of the IEEE and in 2001 received the H.A. Wheeler Award from the IEEE Antennas and Propagation Society.

• About the Authors xixPreface xxiAcknowledgments xxiiiGlossary of Terms xxvIntroduction xxxi1 Antenna System Analysis 11.1 Introduction 11.2 Antenna Radiation and Path Loss 11.3 Polarization 31.3.1 Polarization Efficiency 41.4 Geometry of Satellite Communication Link 51.4.1 Pointing Angles to Satellites 51.4.1.1 The Case for the Elevation-over-Azimuth Antenna 51.4.1.2 The Case for the Declination-over-Hour Angle Antenna 81.4.2 Elevation-over-Azimuth Pattern Angle Correction 101.4.3 Sun Outage 101.4.4 Linear Polarization Twist at Ground Station from Satellite 111.5 Noise in Antennas 121.5.1 Noise Mechanisms 121.5.2 Signal-to-Noise Ratio 131.5.3 Noise Power 131.5.4 Equivalent Noise Temperature 141.5.5 Noise Figure 141.5.6 Antenna Noise Temperature 161.5.7 Noise in a Satellite–Earth Station Link 171.5.8 Antenna Noise Temperature Components 181.5.8.1 Sky Noise 181.5.8.2 Antenna Noise Temperature 211.5.9 Sky Noise Temperature Variation with Ambient Temperature and Humidity 251.6 Interference in Antennas 291.6.1 Introduction 291.6.1.1 Sources of Interference 301.6.1.2 Corrective Filter Application 301.6.2 Interference by the Transmitter 311.6.3 Interference by Tx Signal Power 331.6.4 Interference due to Tx Noise Power 351.7 Passive Intermodulation in Antennas 391.7.1 Brief History 391.7.2 Theory 391.7.2.1 Second-Order PIM – Two Equal Amplitude Transmit Carriers 401.7.2.2 Third-Order PIM – Two Equal Amplitude Transmit Carriers 401.7.2.3 Third-Order PIM – Three Equal Amplitude Transmit Carriers 401.7.2.4 Specific Cases of PIM Frequencies 411.7.2.5 Amplitude of PIMs 411.7.2.6 Causes of PIM in Antennas 451.7.3 Some Interesting Observations 461.7.3.1 Measurement of PIMs 471.8 Link Analysis 471.8.1 Uplink Analysis 471.8.2 Downlink Analysis 501.8.3 EIRP and Power Density 521.9 Digital Communication Link Budget 541.9.1 Link Budget Supplied by Marc R. Björkman for Commercial Satellite Multichannel TV Transmission 54References 552 Reflector Design 572.1 Introduction 572.2 Single Reflector Antenna 592.2.1 Prime Focus Antenna Efficiency Components 602.2.1.1 Phase Error Loss 612.2.1.2 Illumination Loss 622.2.1.3 Spillover Loss 632.2.1.4 Blockage 632.2.1.5 Polarization Loss 642.2.1.6 Reflector Panel Loss 642.2.1.7 Reflection Loss 642.2.1.8 Feed Terminal Losses 642.2.1.9 Summary 642.2.2 General Performance Features 652.3 Two-Reflector Design 652.3.1 Cassegrain and Gregorian Configurations 652.3.2 Antenna Efficiency Components 682.3.2.1 Subreflector Blockage 682.3.2.2 Subreflector Support Structure Blockage 682.3.2.3 Feed Blockage 682.3.2.4 Diffraction Loss 702.3.2.5 General Performance Features 702.3.3 Shaped Reflector Design Considerations 712.3.3.1 General Performance Features of the Shaped System 772.3.4 The Ring Focus Antenna 782.3.4.1 Positive Features of Ring Focus 782.3.4.2 Negative Features of the Ring Focus 782.3.4.3 General Performance Features 792.4 Offset Reflector Antennas 802.4.1 Single Offset Reflector Antenna 802.4.1.1 Cross-pol Matched Feed System for Single Offset Reflector Applications 872.4.2 Horn Reflector 872.4.3 Dual-Offset Antennas – Cassegrain and Gregorian 922.4.4 Dragonian Reflector System 972.5 Characteristics of Antenna Patterns 972.5.1 Concept of Antenna Pattern Gain 1022.6 Antennas with Simultaneous Multiband Feeds 1052.6.1 Single Aperture Feed Horn 1052.6.2 Wideband Feed Horn 1082.6.3 Concentric Aperture Feed Horns 1102.6.4 Dual Aperture Feeds with FSS 1112.7 Selectable Multi-feed Systems 1112.8 Beam Waveguide 1152.8.1 Introduction 1152.8.2 Large Antenna Beam Waveguide 1152.8.3 The Quasi-Beam Waveguide 1222.9 Multibeam Antennas 1232.9.1 Introduction 1232.9.2 The Torus 1262.9.2.1 The Declination Difficulty and Off-Axis Feed Settings 1282.9.2.2 Phase Aberrations in the Feed Horn 1332.9.2.3 Siting the Torus to Other Latitudes 1332.9.2.4 General Performance Features of the Torus 1352.9.3 Shaped Cassegrain CSIRO MBA Antenna 139References 1393 Feed System Design 1413.1 Introduction 1413.2 Linearly Polarized Rx Feed Design and Configurations 1423.2.1 Example Satellite Link 1423.2.2 Single Linear Polarization – with Polarization Rotation 1463.2.3 Dual Linear Polarization – Receive Only 1483.2.4 Linearly Polarized Tx/Rx Feed Design and Configurations 1493.2.5 Linear Polarization – Two Orthogonal Rx and One Tx 1513.2.6 Dual Linear Polarized Rx and Tx 1533.3 Circular Polarization (CP) – Rx-Only Feed Configurations 1573.3.1 OMT + 90 ∘ Power Divider 1583.3.2 Differential Phase Shifter with OMT 1603.3.3 Septum-OMT 1643.3.4 OMT with Rectangular Horn 1673.4 Two-Port Circularly Polarized Rx/Tx Feed Systems 1683.4.1 Four-Port CP Feed Network 1713.5 Polarization Rotation and Switching 1733.5.1 90 ∘ Differential Phase Shifter – CP/LP Selection 1733.5.2 180 ∘ Differential Phase Shifter – LP Angle Adjust Only 1743.5.3 CP/LP and LP Angle Adjust 1763.5.4 90 ∘ Differential Phase Shifter – CP Adjust 1783.5.5 CP/LP Selection – Two-Port Rx/Tx Feed 1783.6 Combined Dual-Polarized Tx/Rx Feed Configuration 1793.6.1 Single QJ and Magic Tee Feed System Network Layout 1803.6.2 Twin-QJ Feed System Layout 1813.6.3 Tri-band Feed Using Twin-QJ and Symmetric OMT 1813.6.4 Combined CP and LP Tx/Rx Feed Configuration 1833.7 Feed System Terminal Characteristics 1853.7.1 VSWR – Effect of Multiple Contributions 1863.7.2 Practical Matching Techniques 1873.7.3 Polarization Discrimination – Axial Ratio and Cross-pol 1883.7.4 Port-to-Port Isolation 1893.7.5 Insertion Loss 1893.7.6 Signal Delay Time 190References 1904 Tracking Feed Systems 1934.1 Introduction 1934.2 Maximum Signal “Search and Track” Methods 1954.2.1 Step Track 1954.2.2 Conical Scan 1964.2.3 Electronic Conical Scan 1964.3 Zero-Signal Track Methods 1994.3.1 Phase–Amplitude Monopulse 1994.3.1.1 TM 01 + TE 01 Mode Pattern 2004.3.1.2 TE 21 Mode Pattern 2024.3.2 TE 21 Mode Coupler Design Concepts 2024.3.2.1 A System Performance Study 2094.3.2.2 Error Channel Path 2124.4 Array Monopulse Feeds 2144.4.1 Four-Horn “Cross” Array 2144.4.2 Four-Horn “Corner” Array 2164.4.3 The Integrated Five-Horn Array 2164.4.4 Polarization Requirements for Monopulse Functions 2214.4.5 Monopulse Detection Methods 2214.4.6 The Impact of the Presence of a ΔAz Cross-Talk Signal 2244.5 Array Analysis and Design 2244.5.1 The Sum of the Array Elements 2284.5.2 The Difference Between Array Element Pairs 2284.5.2.1 The Cross Array – Figure 4.32 2294.5.2.2 The Corner Array – Figure 4.33 2294.5.2.3 The Five-Horn Monopulse Array 231References 2355 Structural and Mechanical 2375.1 Introduction 2375.2 Antenna Configurations 2375.3 Antenna Axis Configurations 2425.3.1 Elevation-over-Azimuth 2425.3.2 X–Y or Cross-Elevation-over-Elevation 2435.3.3 Declination-over-Hour Angle 2455.4 Reflector Support Structures 2485.5 Reflector Geometries 2525.6 Reflector Accuracy 2525.7 Design of Reflector Panels 2575.7.1 Main Reflector Fabrication 2575.7.1.1 Stretched Panels with “Zees” 2575.7.1.2 Stretched Panels with Precision Profiled Radials 2595.7.1.3 Truss Support Construction 2605.7.1.4 Machined Panels 2605.7.1.5 Stretched Panels with Honeycomb Core Between Two Stretched Panels 2605.7.1.6 Metal Spinning Manufacturing 2615.7.1.7 Fiberglass and Carbon Fiber Lay-ups 2625.7.2 Subreflector Fabrication 2635.8 Pointing Accuracy 2645.8.1 Beam Deviation Factor 2675.8.2 Beam Tilt Due to Main Reflector Translation 2715.8.3 Beam Tilt Due to Main Reflector Rotation 2715.8.4 Beam Tilt Due to Subreflector Translation 2715.8.5 Beam Tilt Due to Subreflector Rotation 2725.8.6 Beam Tilt Due to Feed Translation/Rotation 2725.8.7 Subreflector Axial Displacement 2725.9 Structural Alignment 2745.9.1 Orthogonality 2745.10 Panel Alignment 2765.10.1 Theodolite and Precision Drill Tape Panel Setting 2765.10.2 Laser Tracker 2775.10.3 Photogrammetry and Precision Reference Scale 2775.10.4 Microwave Interferometry (Holography) 2775.11 Influences of Weather 2785.12 Mechanical Layout Concepts for Complex Feed Systems 2805.12.1 A Brief Summary of Important Feed Design Considerations 2805.12.2 Sample Feed Design Problem 280References 2836 Antenna Protection 2856.1 Protecting the Feed Against the Elements 2856.1.1 Feed Horn Window Considerations 2856.1.2 Feed Pressurization Principles 2876.1.2.1 Example System Leak Rate Calculation 2886.1.2.2 Leakage of Air from the Feed System 2896.1.3 Waveguide System Dehydration 2916.2 Feed Protection against Rain, Mist, Snow and Ice, and Birds 2936.2.1 Rain-Blower 2936.2.2 Feed Window Material 2956.2.3 Hydrophobic Coatings 2956.2.4 Bird Protection 2956.3 Radomes 2976.3.1 Sandwich Radomes 2986.3.1.1 Construction 2986.3.1.2 Geometry 2986.3.1.3 Electromagnetic Performance 3016.3.2 Solid Laminate Radomes 3016.3.2.1 Construction 3016.3.2.2 Electromagnetic Performance 3026.3.3 Air-Supported Radomes 3026.3.3.1 Construction 3026.3.3.2 Electromagnetic Performance 3036.3.4 Space Frame Radomes 3036.3.4.1 Construction 3036.3.4.2 Electromagnetic Performance 3036.3.4.3 Design Aspects of Metal Space Frame Radomes 3086.3.4.4 Results of Measurements on Antennas Under Metal, MSF, and Dielectric Space Frame, DSF, Radomes 3086.3.4.5 Passive Intermodulation Issues in Metal Space Frame Radomes 3096.3.4.6 Short Comparison of Metal Space Frame and Air-Inflated Radomes 3096.3.5 Selection Criteria 3096.3.5.1 Electromagnetic Performance 3106.3.5.2 Maintenance and Support 3116.3.6 Brief Summary of Radome Features 3116.3.6.1 Reasons for Use 3116.3.6.2 Impact on Antenna Performance by the Radome – Gain, G/T, Sidelobe Envelope 3126.3.6.3 Comparative Radome Attributes 313References 3147 Site Considerations 3157.1 Radiation Hazard 3157.2 Earth Station Site Planning 3217.2.1 Obstructions and Safety 3217.2.1.1 Satellite Link Obscuration Sources 3217.3 Antenna Site Interference Issues 3237.3.1 Terrestrial Interference 3237.3.2 Interfacility Links 3277.3.3 RF Leakage 3277.3.4 Weather 328References 3298 Proof-of-Performance 3318.1 The Specification 3318.2 Basic System Requirements 3328.3 Factory Testing 3328.3.1 Feed System and Performance Features 3338.3.1.1 Feed Patterns 3348.3.1.2 Polarization Discrimination/Isolation – Linearly Polarized Feed Configurations 3348.3.1.3 Axial Ratio – Circularly Polarized Feed Configurations 3358.3.1.4 Return Loss 3358.3.1.5 Port-to-Port Isolation 3358.3.1.6 Insertion Loss 3358.3.1.7 Time or Group Delay 3358.3.1.8 Passive Intermodulation 3368.3.1.9 RF Leak 3368.3.1.10 Mechanical Details 3368.3.1.11 Polarization Control – Remote or Manual 3368.3.1.12 Pressurization Leak Rate 3368.3.1.13 Dimensional Check of Feed Assembly 3368.3.2 Feed System – Sample Measurements 3378.3.2.1 Return Loss Measurement 3378.3.2.2 Insertion Loss Measurement 3378.3.2.3 Port-to-Port Isolation Measurement 3378.3.2.4 Polarization Discrimination (Cross-pol) Measurement 3378.3.2.5 Pattern Measurements 3388.3.2.6 Possible Difficulties That One Can Encounter in Feed Measurement Include 3388.3.3 Reflector System 3438.3.4 Effects of Reflector Errors 3468.3.4.1 Panel Errors 3468.3.5 Other Subsystems 3488.3.6 Outdoor Test Range 3498.3.6.1 Length 3498.3.6.2 Ground Reflections 3508.3.6.3 Advantages of Range Measurements 3548.3.6.4 Noise Temperature Measurements 3548.3.6.5 Summary of Range Test Activities 3558.4 Customer Site Preparations 3578.4.1 Pedestal Alignment Check 3578.4.2 Reflector and Feed System Mechanical Alignment Check 3578.4.3 Ancillary Equipment Function Check – Control System, LNAs, HPAs 3588.4.4 IFL Signal Path Integrity 3598.4.5 Pretest Preparations 3598.4.5.1 Angular Range Limits for Antenna Patterns 3598.4.5.2 Applicability of Radio Star Observations to Measure G/T and Gain 3608.4.6 Test Equipment, Location, Setup, and Function Check 3618.5 Preliminary RF Checks and Example Difficulties 3628.5.1 Sum Patterns 3628.5.2 Difference Patterns 3678.5.3 Antenna Gain 3708.5.4 Antenna Noise Temperature 3718.5.5 Radio Star Track Check 3728.5.6 IFL Signal Paths 3738.5.6.1 Unexpected High RL (Return Loss) Values 3748.5.6.2 Mode Spikes in RL Response 3748.6 Formal On-Site RF Antenna Tests 3768.6.1 Antenna Patterns – Sum, Difference, Cross-pol 3768.6.2 Monopulse Tracking Sensitivity 3768.6.3 Antenna Noise Temperature 3768.6.4 Antenna System G/T, Noise Temperature, and Gain 3768.6.4.1 Satellite Link Method 3768.6.4.2 Beamwidth Method 3768.6.4.3 Pattern Integration 3808.6.4.4 Radio Star Method 3808.6.5 Transmit Uplink Gain and EIRP Stability 3848.7 Measurement Accuracy 384Appendix A Appendices 385A. 1 Feed System Insertion Loss Determination 385A.. 1 Test Equipment Necessary for the Measurement 385A.1. 2 Calibration of Low Noise Amplifier Against Clear Zenith Sky Temperature as Seen by a Standard Gain Horn 385A.1. 3 Determination of the Feed System Insertion Loss 387A. 2 Determination of Antenna Gain and G/T Using Calibrated Radio Stars 389A.2. 1 Test Equipment 389A.. 2 Configuring and Checking the Test Setup Prior to the Measurement 389A.2. 3 Formal Measurement Procedure 394A.2. 4 Data Analysis 396A.2.4. 1 Basis for the Measurement Method 396A..4. 2 Radio Star Flux Densities 396A.2. 5 Correction Factors 397A.2.5. 1 Time Dependence of the Star Flux Density 397A..5. 2 Frequency Dependence of the Star Flux Density 397A.2.5. 3 Atmospheric Absorption 397A.2.5. 4 Angular Extension of Radio Stars 398A.2.. 5 Polarization Correction 398A.2.5. 6 Correction to y star Due to Receiver Noise 398A.2. 6 The Final Expression for G/T and Gain 399A.2.6. 1 Antenna System Noise Temperature 399A..6. 2 Antenna System Gain 400A.2.6. 3 Correction to y sky Due to Receiver Noise 401A.3 Pointing Angles to Radio Star Positions 401A.3.1 Introduction 401A.3.2 The Coordinate System and Time 402A.3.3 Positional Geometry of the Sun Over the Earth 405A.4 Radio Star Information 405A.4.1 Star Flux Densities 405A.4.2 Star Flux Change with Frequency – Spectral Index γ 408A.4.3 Correction for Atmospheric Attenuation 412A.4.4 Correction for Star Polarization 412References 413Index 415