Communications Payload Design and Satellite System Architecture: Bent Pipe and Digital Processor-based Course Sampler

Communications Payload Design and Satellite System Architecture: Bent Pipe and Digital Processor-based Course Sampler
http://www.ATIcourses.com/schedule.htm http://www.aticourses.com/Communications_Payload_Design_etc.html ATI Course Schedule: ATI's CONOPS: Satellite Communications Payload Design and System Architecture Instructor: Bruce Elbert
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COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-2 Objectives and Approach • Instructor: – Bruce Elbert, President, Application Technology Strategy, Inc. – Hughes Satellite, 1972 - 1999 – BEE, City Univ. of NY, MSEE, Univ. of Md., MBA, Pepperdine Univ. – Contact: tel +1 (310) 918-1728, email bruce@applicationstrategy.com • Objectives: – Develop a systems engineering approach for satellite communications – Explain the techniques and tools used to design commercial communications payloads – Provide the framework for the overall system and ground segment • Approach: – Blend the theoretical with the practical – Provide both the big picture and a detailed view – Interact and exchange concepts and methodologies
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-3 Course Outline • Comm Payloads and Service Requirements • Systems Engineering to Meet Service Requirements • Bent-pipe Repeater Design • Spacecraft Antenna Design and Performance • Comm Payload Performance Budgeting • On-board Digital Processor Technology • Multi-beam Antennas • RF Interference and Spectrum Management • Ground Segment Selection and Optimization • Earth Station and User Terminal Tradeoffs • Performance and Capacity Assessment • Satellite System Verification Methodology
Satellite System Definitions VSATs or other user terminals Space segment Ground segment TT&C earth station Satellite control center Hub or gateway earth station COPYRIGHT © 1997 • BRUCE R. ELBERT (satellite operator) (network operator or user)
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-5 Kepler’s Laws of Planetary Motion • First Law: The orbit of each planet is an ellipse, with the Sun at one focus. • Second Law: The line joining the planet and the Sun sweeps out equal areas in equal times. • Third Law: The square of the period of a planet is proportional to the cube of its mean distance from the Sun. v h P = 1.659 10-4 (6378 + h)3/2 minutes
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-6 Earth Satellite Orbit Options Orbit definition Altitude range, km Period, hrs • Low earth orbit (LEO) 150 - 1,000 1.5 - 1.8 • Medium earth orbit (MEO) 5,000 - 10,000 3.5 - 6 • Geosynchronous earth orbit 36,000 24 – Inclined – Geostationary earth orbit (GEO) LEO MEO GEO
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-7COPYRIGHT © 2000 • BRUCE R. ELBERT Plasma sheet Polar wind Plasma sphere Polar cusp Bow shock Magnetosheath Magnetopause Solar wind Van Allen Belts Space Environment
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-8 Radiation Dose vs. Altitude (5 mil Al thickness) 0 2000 4000 6000 8000 10000 10 103 105 107 109 Dose, Rads/yr Altitude, km
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-9 Orbit Period and Delay vs. Altitude 0 5 10 15 20 25 0 10000 20000 30000 40000 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 500 1000 LEO Altitude, km Altitude, km Hours 7.5 75 150 225 270 Delay, ms
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-10 LEO Constellation for Iridium • 66 satellites • 6 polar orbits • Inter-satellite links
Iridium Spacecraft (Motorola and Lockheed-Martin) PD-1-01-11
PD-1-12 http://www.faqs.org/sec-filings/100602/Iridium- Communications-Inc_8-K/dex992.htm
GEO Orbit “Slot” for Domestic Service COPYRIGHT © 1999 – 2001 • BRUCE R. ELBERT • 24 hour orbit requires stationkeeping operations – Maintain orbit in equatorial plane (N/S stationkeeping) – Compensate for east-west drift and eccentricity – Satellite service defined by antenna beam coverage • Lifetime determined by stationkeeping fuel reserve PD-1-01-13
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-14 Antenna Beam Options Area Coverage Multiple Spot Beams GW GW GW GW GW GW
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-15 Star and Mesh Topologies Hub Remote Remote Remote Remote Remote Remote Peer node Peer node Peer node Peer node Control In either topology, links can be established on demand or fixed
Large-capacity GEO Spacecraft PD-1-01-16 Boeing 702 15 kW 4700 kg at launch SS/Loral 1300S 19 kW 6200 kg at launch EADS Astrium 14 kW 6000 kg at launch LM A 2100 AX 3600 kg at launch
Major Satellite Components • Payload subsystems – Repeater (receivers, multiplexers, amplifiers, processing and switching) – Antennas (reflectors, feeds, feed networks, support structure and pointing mechanisms) • Bus subsystems – Tracking, telemetry, command and ranging (TTC&R) – Solar panels – Batteries – Reaction control system (propulsion) – Attitude and spacecraft control processing – Thermal control and structure PD-1-01-17
Lockheed-Martin A2100 Three-Axis Spacecraft PD-1-01-18
Lockheed-Martin A2100 Block Diagram PD-1-01-19
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-20 Typical Spacecraft Mass Allocation • Geostationary orbit • 15 year mission • Three axis spacecraft • ~2000 kg total dry mass • ~8000 watts total (EOL) • Standard payload type Repeater Antenna Power TT&C ACS Propulsion Thermal Structure Harness
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-21 Typical Spacecraft Power Allocation • GaAs solar cells • Flat solar panels • NiH2 batteries • 15 year operation • ~8000 watts EOL Repeater TT&C ACS Propulsion Power Thermal
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-22 Satellite Size v. Capabilities Hypothetical class of satellite Conceptual number of Transponders General Range of EOL Power General Range of Launch Mass, kg “Small” 24 to 36 4 to 6 kW 1500 to 2500 “Medium” 48 to 72 8 to 10 kW 3000 to 4000 “Large” 90 to 120 12 to 22 kW 4500 to 6000
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-23 UHF L S C X Ku Ka Q V 1 10 100 GHz0.1 Microwave 303 Microwave Spectrum (log scale)
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-24 Total attenuation toward zenith, dB Propagation Effects on Satellite Systems at Frequencies Below 10 GHz, NASA Publication 1108(02) 1987 Frequency, GHz H2O O2 O2 H20 Clear Air Attenuation    sin w0 a a2a8 A Variation of total attenuation as a function of elevation angle,  >10
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-25 ITU-DAH Rain Model 75 55 37 26 14 25 mm/hr, .01% of the time
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-26 Elevation Angle Dependence Rain Cell (rain rate) ),,( FplrrfA pl el el
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-27 Rain Attenuation (temperate climate) Availability 99.5% 98.0% 10° 20° 45° 10° 20° 45° 1 10 100 Frequency, GHz Elevation angle 2 4 8 20 40 80 50 40 30 20 10 0 Attenuation, dB
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-28 Typical Margin for Rain Fade (12 GHz) Rain Intensity Margin region mm/hr at 99.8% A 6 0.3 B 12 0.5 C 15 0.7 D 19 0.9 E 22 1.1 F 28 1.4 G 30 1.5 H 32 1.7 J 35 1.8 K 42 2.2 L 60 3.2 M 63 3.4 N 98 4.8 P 145 5.8
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-29 Rain Attenuation Solutions • Ku band (14/12 GHz) – Link margin » Satellite EIRP » Dish size – Uplink power control – Automatic Gain Control (AGC) in spacecraft – Antenna feed blower – Site selection (rain zone) • Ka band (30/20 GHz) – Link margin » Satellite EIRP • Spot beams • Dynamic power » Dish size – Uplink power control – AGC – Dynamic data/coding rate – Antenna feed blower – Radome – Site selection » Rain zone » Diversity • Site • Satellite
Site (Space) Diversity D D PD-1-30
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-31 Further Details on Propagation • Ionospheric effects (below 10 GHz) – Faraday rotation of linear polarization – day to night variation greatest during peaks of sun spot cycle – Ionospheric scintillation – most pronounced near the geomagnetic equator (tropical regions) – frequency selective fading during evening and morning transitions of the F layers • Tropospheric effects (low elevation angles) – Absorption – Scintillation – Ducting (Horizontal path) – Rain – ITU-R Dissanayake, Allnut, Haidara (DAH) model
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-32 Maximum Ionospheric Effects [US one-way paths at 30 elevation, NASA 1108(2) Table 2.2] Effect 100 MHz 300 MHz 1 GHz 3 GHz 10 GHz Faraday rotation 30 rotations 3.3 rotations 108° 12 1.1° Excess time delay 25 s 2.8 s 0.25 s 28 ns 2.5 ns Absorp (polar) 5 dB 1.1 dB .05 dB .006 dB .0005 dB Absorp (mid Lat) <1 dB .1 dB <.01 dB <.001 dB <.0001 dB Disper .4 ps/Hz .015 ps/Hs .0004 ps/Hz .000015 ps/Hz .0000004 ps/Hz
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-33 Communication Payload Technology (Analog and Digital)  Analog repeater – Bent pipe (no change in format; uplink and downlink noise combine) – Supports any modulation and multiple access – Limited routing capability – Excellent dynamic range; impairments can aggregate  Digital processing repeater – Channel routing or packet switching – Tailored to multiple access (and modulation) – Separates uplink from downlink – Excellent routing (and switching) capability – Limited dynamic range
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-34 Analog (Bent-pipe) Repeater • Standard design for FSS and BSS satellites • Simple design, simple operation • Very flexible • Network optimization limited Wideband receiver (500 MHz bandwidth) F1 Pre A F1 F3 Pre A F3 F5 Pre A F5 F6 Pre A F6 F4 Pre A F4 F2 Pre A F2 LPF 5.925-6.425 GHz 3.7-4.2 GHz
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-35 Frequency Plan for Bent Pipe Repeater 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 Uplink frequency range Downlink frequency range Fup(low) Fup(hi) Fdwn(low) Fdwn(hi) Channel spacing Transponder bandwidthGuardband Not to scale: guardband typically 10% of channel spacing Translation frequency
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-36 The Spacecraft Antenna System • Area coverage antenna – Most common approach for bent pipe repeaters – Coverage area is similar to local broadcasting (but with less variation of received signal power) • Coverage is defined by the antenna gain pattern
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-37 Digital Signal Processing Repeater Design • Need for flexible payload architecture – Channel routing – On-demand reconfiguration – Demod/remod performance – Beam forming, multiple and flexible • Constraints – Signal structure (multiplex, modulation and multiple access) – Bandwidth – Processor speed and complexity – Power and weight – Impairments – Dynamic range
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-38 Broadband Processing Payload Rcv feed network Tx feed network Rcvr Rcvr Rcvr Rcvr Rcvr Rcvr HPA HPA HPA HPA HPA HPA Digital Processor: A/D Demod Routing and Switching Multiplexing Modulation Beam forming D/A Receivefeedsandaperture Transmitfeedsandaperture Low-power transmission line High-power transmission line Active redundancy not shown Upconv or driver Upconv or driver Upconv or driver Upconv or driver Upconv or driver Upconv or driver
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-39 Inmarsat-4 Global Coverage
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-40 Course Outline • Comm Payloads and Service Requirements • Systems Engineering to Meet Service Requirements • Bent-pipe Repeater Design • Spacecraft Antenna Design and Performance • Comm Payload Performance Budgeting • On-board Digital Processor Technology • Multi-beam Antennas • RF Interference and Spectrum Management • Ground Segment Selection and Optimization • Earth Station and User Terminal Tradeoffs • Performance and Capacity Assessment • Satellite System Verification Methodology
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-41 The Microwave Link in Satellite Communications • Frequencies above 1 GHz (but less than 60 GHz) • Line-of-sight propagation • Low received signal level due to large distance Pr Pt R0 2 Pr R0Pt Power Flux Density, Watts/sq meter  Pr A = Pt 4pR0 2
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-42 Path Geometry (GEO Link)  coscos29577.01107.42643 3 0 R R0 h km Where R0 = slant range (distance between satellite and earth station) h = GEO altitude (35,788,293 meters)  = Earth station latitude  = Earth station relative longitude
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-43 Gain and Effective Area of a Circular Aperture                     p    p   p 4 4 2 2 2 G AA DA G E D
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-44 Antenna “Capture” Area • Receive antenna “captures” power through its effective area • Transmit antenna is a reciprocal device (yielding the same performance as in receive) R Pt AE 2 2 2 4 4 4       p   p   p  R GPP G AA A R P P rtr r E E t r
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-45 Polarization of the EM Wave Linear polarization: (a) vertical (b) horizontal Circular polarization (c) Left hand (d) Right hand (d) λ
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-46 Vertically polarized horn Horizontally polarized horn a b Waveguide and Horn Polarization (Linear Polarization) c =2a b ~ a/2
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-47 Co and CrossPolarization Co-polarized signal component Cross-polarized signal component Relative polarization angle, degrees Relative received signal 0 10 20 30 40 50 60 70 80 90 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-48 Linear CrossPolarization Isolation Cross-Polarization Isolation 0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 8 9 10 11 Feed offset angle, degrees Isolation,dB
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-49 Properties of Circular Polarization • Special case of elliptical polarization • Polarization sense established within the transmit feed system • Little or no impact from the Ionosphere • Isolation properties generally inferior to linear Axial ratio = 20 log (a/b)
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-50 Polarization Coupling Polarization type Linear Circular Linear -10log [Cos2] dB -3 dB Circular (elliptical) -3 dB Graph Ref: Johnson, Antenna Engineering Handbook, FIG 23-7, p 23-9
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-51 Depolarization in Rain (Ku – Ka) Cloud and Rain Cell Geometry affect V and H polarizations differently Circular Polarization is composed of V and H polarizations
COPYRIGHT © 1999 - 2011 • BRUCE R. ELBERT PD-1-52 Link Degradation http://descanso.jpl.nasa.gov/Propagation/1082/1082ch1.pdf
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