Professional Development Short Course On:

             Satellite Communications Systems Engineering


                   ...
Satellite Communication Systems Engineering
              A comprehensive, quantitative tutorial designed for satellite pr...
www.ATIcourses.com

Boost Your Skills                                             349 Berkshire Drive
                    ...
Outline
PART 1: THE SPACECRAFT AND ITS ORBIT
 1. Mission Analysis
 2. Transfer Orbit
 3. Orbital Perturbations and Station...
The RF Link
  (Excerpt)




    3         Satellite Engineering Research Corporation
Antenna pattern, beamwidth, and gain
           sidelobes           main lobe            ΩA = total solid angle of radiati...
Example: Earth terminal antenna

                                                     Ku band downlink frequency
         ...
Equivalent isotropic radiated power (EIRP)
The equivalent isotropic radiated power (EIRP) is the transmit power of a hypot...
Example 1

  numeric form                              logarithmic (dB) form



   Gt = 100                            [Gt...
Example 2




[PHPA] = 10 log10(100 W) = 20 dBW

[Pin] = [PHPA] – [L] = 20 dBW – 1 dB = 19 dBW

[EIRP] = [Gt] + [Pin] = 60...
Figure of Merit (G / T)
The ratio of the receive antenna gain G to the total system temperature T is
called the “figure of...
Satellite communications payload architecture




                     10      Satellite Engineering Research Corporation
Transponder




    11        Satellite Engineering Research Corporation
Satellite transponder frequency plan (C-band)




                     12       Satellite Engineering Research Corporation
Typical satellite data
                                                          Telstar 5 97º W C/Ku band
Began service: ...
Satellite EIRP footprint




P = 100 W      [ P ] = 20 dBW     [ G ] = 30 dB

[ EIRP ] = [ G ] + [ P ] = 30 dB + 20 dBW = ...
Satellite Figure of Merit G / T




T = 630 K       [ T ] = 28 dBK     [ G ] = 30 dB

[ G / T ] = [ G ] – [ T ] = 30 dB – ...
Earth-satellite geometry
                           Telstar 5 97º W C / Ku band
City/Country                       Latitud...
Free space loss

The free space loss takes into account that electromagnetic waves spread
out into spherical wavefronts as...
Example
Problem: Determine the free space loss for a Ku band downlink between Telstar 5 at 97°
W Longitude and Los Angeles...
Received carrier power
Received carrier power
                                       Ae P
                                ...
Example
Problem: Determine the received carrier power for the Ku band downlink between Telstar 5
and an Earth terminal in ...
Noise power

Thermal noise power in bandwidth B

                       N = N0 B = kB T B

where the spectral noise densit...
Link budget equation

Carrier power
                             EIRP Gr
                          C=
                    ...
Link budget equation (continued)

The link budget equation is expressed in logarithmic (dB) form as follows
(dB values ind...
Combined uplink and downlink

Only thermal noise (Average White Gaussian Noise)
                        −1         −1     ...
Power flux density

The EIRP of the uplink Earth station antenna must be adjusted to match an
acceptable power flux densit...
Example
Problem: For an uplink between an Earth station in Washington, DC and
Telstar 5, the EIRP is 79.0 dBW, the slant r...
Example link budget
Signal architecture                                             Satellite

Information bit rate       ...
Example link budget (continued)
                                                  Uplink


Earth station transmit terminal...
Example link budget (continued)
                                                   Downlink


Earth station receive termin...
Example link budget (continued)
                       Combined uplink and downlink




    C/N (uplink)                  ...
Power levels in satellite link
-30.0 dBW       Output of modulator
                and upconverter              Power
    ...
α = half power beamwidth
          RF link (summary)                           λ = wavelength
                            ...
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ATI Courses Satellite Communications Systems Engineering Professional Development Short Course Sampler

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ATI Courses Satellite Communications Systems Engineering course sampler. This three-day course is designed for satellite communications engineers, spacecraft engineers, and managers who want to obtain an understanding of the "big picture" of satellite communications. Each topic is illustrated by detailed worked numerical examples, using published data for actual satellite communications systems. The course is technically oriented and includes mathematical derivations of the fundamental equations. It will enable the participants to perform their own satellite link budget calculations. The course will especially appeal to those whose objective is to develop quantitative computational skills in addition to obtaining a qualitative familiarity with the basic concepts.

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ATI Courses Satellite Communications Systems Engineering Professional Development Short Course Sampler

  1. 1. Professional Development Short Course On: Satellite Communications Systems Engineering Instructor: Dr. Robert A. Nelson ATI Course Schedule: http://www.ATIcourses.com/schedule.htm ATI's Satellite Communications Systems Engineering: http://www.aticourses.com/satellite_communications_systems.htm 349 Berkshire Drive • Riva, Maryland 21140 888-501-2100 • 410-956-8805 Website: www.ATIcourses.com • Email: ATI@ATIcourses.com
  2. 2. Satellite Communication Systems Engineering A comprehensive, quantitative tutorial designed for satellite professionals Course Outline March 16-18, 2009 1. Mission Analysis. Kepler’s laws. Circular and Boulder, Colorado elliptical satellite orbits. Altitude regimes. Period of revolution. Geostationary Orbit. Orbital elements. Ground June 15-17, 2009 trace. 2. Earth-Satellite Geometry. Azimuth and elevation. Beltsville, Maryland Slant range. Coverage area. 3. Signals and Spectra. Properties of a sinusoidal $1740 (8:30am - 4:30pm) wave. Synthesis and analysis of an arbitrary waveform. "Register 3 or More & Receive $10000 each Fourier Principle. Harmonics. Fourier series and Fourier Off The Course Tuition." transform. Frequency spectrum. 4. Methods of Modulation. Overview of modulation. Carrier. Sidebands. Analog and digital modulation. Need for RF frequencies. 5. Analog Modulation. Amplitude Modulation (AM). Frequency Modulation (FM). 6. Digital Modulation. Analog to digital conversion. Instructor BPSK, QPSK, 8PSK FSK, QAM. Coherent detection and carrier recovery. NRZ and RZ pulse shapes. Power spectral Dr. Robert A. Nelson is president of Satellite density. ISI. Nyquist pulse shaping. Raised cosine filtering. Engineering Research Corporation, a consulting firm in 7. Bit Error Rate. Performance objectives. Eb/No. Bethesda, Maryland, with clients in both Relationship between BER and Eb/No. Constellation commercial industry and government. diagrams. Why do BPSK and QPSK require the same Dr. Nelson holds the degree of Ph.D. in power? physics from the University of Maryland 8. Coding. Shannon’s theorem. Code rate. Coding gain. and is a licensed Professional Engineer. Methods of FEC coding. Hamming, BCH, and Reed- He is coauthor of the textbook Satellite Solomon block codes. Convolutional codes. Viterbi and Communication Systems Engineering, sequential decoding. Hard and soft decisions. 2nd ed. (Prentice Hall, 1993) and is Technical Editor of Concatenated coding. Turbo coding. Trellis coding. Via Satellite magazine. He is a member of IEEE, AIAA, 9. Bandwidth. Equivalent (noise) bandwidth. Occupied APS, AAPT, AAS, IAU, and ION. bandwidth. Allocated bandwidth. Relationship between bandwidth and data rate. Dependence of bandwidth on methods of modulation and coding. Tradeoff between bandwidth and power. Emerging trends for bandwidth Additional Materials efficient modulation. In addition to the course notes, each participant will 10. The Electromagnetic Spectrum. Frequency bands receive a book of collected tutorial articles written by used for satellite communication. ITU regulations. Fixed the instructor and soft copies of the link budgets Satellite Service. Direct Broadcast Service. Digital Audio discussed in the course. Radio Service. Mobile Satellite Service. 11. Earth Stations. Facility layout. RF components. Network Operations Center. Data displays. Testimonials 12. Antennas. Antenna patterns. Gain. Half power beamwidth. Efficiency. Sidelobes. “Great handouts. Great presentation. 13. System Temperature. Antenna temperature. LNA. Great real-life course note examples Noise figure. Total system noise temperature. and cd. The instructor made good use 14. Satellite Transponders. Satellite communications of student’s experiences." payload architecture. Frequency plan. Transponder gain. TWTA and SSPA. Amplifier characteristics. Nonlinearity. Intermodulation products. SFD. Backoff. “Very well prepared and presented. 15. The RF Link. Decibel (dB) notation. Equivalent The instructor has an excellent grasp isotropic radiated power (EIRP). Figure of Merit (G/T). Free of material and articulates it well” space loss. WhyPower flux density. Carrier to noise ratio. The RF link equation. 16. Link Budgets. Communications link calculations. “Outstanding at explaining and Uplink, downlink, and composite performance. Link budgets defining quantifiably the theory for single carrier and multiple carrier operation. Detailed underlying the concepts.” worked examples. 17. Performance Measurements. Satellite modem. Use of a spectrum analyzer to measure bandwidth, C/N, “Fantastic! It couldn’t have been more and Eb/No. Comparison of actual measurements with relevant to my work.” theory using a mobile antenna and a geostationary satellite. 18. Multiple Access Techniques. Frequency division multiple access (FDMA). Time division multiple access “Very well organized. Excellent (TDMA). Code division multiple access (CDMA) or spread reference equations and theory. Good spectrum. Capacity estimates. examples.” 19. Polarization. Linear and circular polarization. Misalignment angle. “Good broad general coverage of a 20. Rain Loss. Rain attenuation. Crane rain model. Effect on G/T. complex subject.” Register online at www.ATIcourses.com or call ATI at 888.501.2100 or 410.956.8805 Vol. 97 – 53
  3. 3. www.ATIcourses.com Boost Your Skills 349 Berkshire Drive Riva, Maryland 21140 with On-Site Courses Telephone 1-888-501-2100 / (410) 965-8805 Tailored to Your Needs Fax (410) 956-5785 Email: ATI@ATIcourses.com The Applied Technology Institute specializes in training programs for technical professionals. Our courses keep you current in the state-of-the-art technology that is essential to keep your company on the cutting edge in today’s highly competitive marketplace. Since 1984, ATI has earned the trust of training departments nationwide, and has presented on-site training at the major Navy, Air Force and NASA centers, and for a large number of contractors. Our training increases effectiveness and productivity. Learn from the proven best. For a Free On-Site Quote Visit Us At: http://www.ATIcourses.com/free_onsite_quote.asp For Our Current Public Course Schedule Go To: http://www.ATIcourses.com/schedule.htm
  4. 4. Outline PART 1: THE SPACECRAFT AND ITS ORBIT 1. Mission Analysis 2. Transfer Orbit 3. Orbital Perturbations and Stationkeeping 4. The Spacecraft Environment 5. Earth-Satellite Geometry 6. Constellation Design PART 2: PRINCIPLES OF SATELLITE COMMUNICATION 7. Signals and Spectra 8. Analog Modulation 9. Digital Modulation 10. Coding 11. The Electromagnetic Spectrum 12. The RF Link 13. Earth Stations 14. Multiple Access 15. Antennas 16. System Temperature 17. Polarization 18. Rain Loss PART 3: APPLICATIONS TO SATELLITE COMMUNICATION SYSTEMS 19. Link Budgets for Geostationary Satellites 20. Link Budgets for Nongeostationary Satellites 2 Satellite Engineering Research Corporation
  5. 5. The RF Link (Excerpt) 3 Satellite Engineering Research Corporation
  6. 6. Antenna pattern, beamwidth, and gain sidelobes main lobe ΩA = total solid angle of radiation Ω = solid angle between HP points gain G α = half power D Ω − 3 dB points beamwidth ΩA An isotropic antenna radiates Beamwidth shows size of beam. equally in all λ λ directions like a HPBW = α = k = 70 ° where k = antenna taper factor light bulb D D Ω=4π Gain shows relative strength of radiation. The maximum (boresight) gain is 4π 4π 29, 000 4π ⎛π D ⎞ 2 G =η * = η′ = =η 2 A =η ⎜ ⎟ where η*, η′ , η = measures of antenna efficiency ΩA Ω α2 λ ⎝ λ ⎠ Gain and beamwidth are linked: As the gain increases, the beamwidth decreases, and vice versa. 4 Satellite Engineering Research Corporation
  7. 7. Example: Earth terminal antenna Ku band downlink frequency f = 12 GHz c 3 × 108 m/s λ= = = 0.025 m f 12 × 109 Hz λ 0.025 m HPBW = α = 70° = 70° = 0.35° D 5.0 m 2 ⎛π D ⎞ ⎛ π 5.0 m ⎞ 2 G =η ⎜ = 0.60 ⎜ = 237,000 ⎝ λ ⎟⎠ ⎝ 0.025 m ⎟ ⎠ [G ] = 10 log10 (237,000) = 53.7 dB Prime Focus Feed; 5 meter reflector; Tx and Rx C-Band gain 46 dB; Beamwidth = 1o Ku-Band gain 54 dB; Beamwidth = 0.4o 5 Satellite Engineering Research Corporation
  8. 8. Equivalent isotropic radiated power (EIRP) The equivalent isotropic radiated power (EIRP) is the transmit power of a hypothetical antenna radiating equally in all directions (like a light bulb) so as to have the same power flux density over the coverage area as the actual antenna. The power flux density of the actual antenna is P η * Pin 4π Pin P Φ= = =η* = Gt in 2 S ΩA d 2 Ω A 4π d 2 4π d where η* is the antenna power loss efficiency, P = η* Pin is the transmitted power, S is the total coverage area at distance d, ΩA is the antenna beam solid angle, and Gt = η* (4π / ΩA ) is the transmit gain. By the definition of EIRP EIRP Φ= 4π d 2 Therefore, EIRP = Gt Pin The EIRP is the product of the antenna transmit gain and the power applied to the input terminals of the antenna. The antenna efficiency η* is absorbed in the definition of gain. 6 Satellite Engineering Research Corporation
  9. 9. Example 1 numeric form logarithmic (dB) form Gt = 100 [Gt] = 10 log10(100) = 20.0 dB Pin = 50 W [Pin] = 10 log10 (50 W) = 17.0 dBW EIRP = Gt Pin [EIRP] = [Gt] + [Pin] = (100)(50 W) = 20.0 dB + 17.0 dBW = 5000 W = 37.0 dBW 10 log10(5000 W) = 37.0 dBW 7 Satellite Engineering Research Corporation
  10. 10. Example 2 [PHPA] = 10 log10(100 W) = 20 dBW [Pin] = [PHPA] – [L] = 20 dBW – 1 dB = 19 dBW [EIRP] = [Gt] + [Pin] = 60 dB + 19 dBW = 79 dBW 8 Satellite Engineering Research Corporation
  11. 11. Figure of Merit (G / T) The ratio of the receive antenna gain G to the total system temperature T is called the “figure of merit.” [G/T]=[G]–[T] (dB/K) where [ G ] = receive antenna gain (dB) [ T ] = total system temperature (dBK) The figure of merit is independent of the point where it is calculated. However, the gain and system temperature must be specified at the same point. Example: Suppose the antenna gain is 53.7 dB and the system temperature is 150 K. Then [ T ] = 10 log10(150 K) = 21.7 dBK [ G / T ] = [ G ] – [ T ] = 53.7 dB – 21.7 dBK = 32.0 dB/K 9 Satellite Engineering Research Corporation
  12. 12. Satellite communications payload architecture 10 Satellite Engineering Research Corporation
  13. 13. Transponder 11 Satellite Engineering Research Corporation
  14. 14. Satellite transponder frequency plan (C-band) 12 Satellite Engineering Research Corporation
  15. 15. Typical satellite data Telstar 5 97º W C/Ku band Began service: 7/ 97 Station-keeping ± 0.05 degrees EIRP (dBW) C- Ku- Mission Life 12 years band band Transponders: 24 C-band @ 36 MHz CONUS 38.8 48.3 4 Ku-band @ 54 MHz Alaska 33.7 39.1 24 Ku-band @ 27 MHz Hawaii 33.8 46.4 Coverage: Continental US, Alaska, Hawaii, Puerto Rico, the Caribbean, and into Canada and Latin America. Puerto Rico/U.S. Virgin Islands 34.0 44.9 Mexico 35.9 43.6 Markets: Strong broadcast and syndication neighborhood anchored by ABC and FOX; host to SNG, data, business television, Internet, Southern Canada 37.0 44.3 direct-to-home programming and digital data applications Caribbean 34.3 43.4 Orbital Transponders Useable Power Location Bandwidth G/T (dB/K) C- Ku- band band 97 degrees W 24 C-band 36 MHz 20 W nominal CONUS 0.4 1.2 4 Ku-band 54 MHz 100 W nominal Alaska -8.2 -5.9 24 Ku-band 27 MHz 100 W nominal Hawaii -5.2 0.6 Puerto Rico/U.S. Virgin Islands -3.7 0.7 Saturation Flux Density - Typical CONUS -71 to -92 (dBW/m²) at C-band adjustable in 1 dB steps Mexico -3.5 -3.5 Southern Canada -2.3 -0.6 -75 to -96 (dBW/m²) at Ku-band adjustable in 1 dB steps Caribbean -3.5 -2.3 Polarization Orthogonal linear polarization at C-band and Ku-band. Frequency Band 4/6 GHz and 12/14 GHz Ku-band Optional "Automatic Level Control" Mode Mitigates the effects of uplink rain fade by maintaining the transponder at a specific fixed operating point between saturation and 8 dB input backoff. 13 Satellite Engineering Research Corporation
  16. 16. Satellite EIRP footprint P = 100 W [ P ] = 20 dBW [ G ] = 30 dB [ EIRP ] = [ G ] + [ P ] = 30 dB + 20 dBW = 50 dBW (COC) 14 Satellite Engineering Research Corporation
  17. 17. Satellite Figure of Merit G / T T = 630 K [ T ] = 28 dBK [ G ] = 30 dB [ G / T ] = [ G ] – [ T ] = 30 dB – 28 dBK = 2 dB/K (COC) 15 Satellite Engineering Research Corporation
  18. 18. Earth-satellite geometry Telstar 5 97º W C / Ku band City/Country Latitude W Longitude Azimuth Elevation Example: Earth terminal in Los Angeles Anchorage, AK/USA 61.22 149.90 123.52 8.3 Boston, MA/USA 42.21 71.03 215.82 34.6 cos γ = cos φ cos ∆λ Calgary/Canada 51.08 114.08 158.45 29.3 Dallas, TX/USA 32.46 96.47 180.37 52.2 = cos(34.03°) cos(118.14° − 97.0°) Guatemala City/Guatemala 14.63 90.52 204.71 71.2 = 0.7730 Halifax/Canada 44.65 63.60 223.21 28.8 Havana/Cuba 23.12 82.42 213.52 58.3 γ = 39.38° Honolulu, HI/USA 21.32 157.83 101.44 18.8 sin ∆λ sin Az = sin γ Houston, TX/USA 29.45 95.21 183.28 55.6 Jacksonville, FL/USA 30.19 81.39 208.53 50.9 sin(118.14° − 97.0°) Los Angeles, CA/USA 34.03 118.14 145.36 44.4 = Merida/Mexico 20.97 89.62 199.81 64.0 sin(39.38°) Mexico City/Mexico 19.42 99.17 173.65 67.1 = 0.5685 Miami, FL/USA 25.46 80.11 214.78 54.8 Nassau/Bahamas 25.08 77.33 220.17 53.3 Az = 180° − 34.64° = 145.36° cos γ − RE / r New York, NY/USA 40.43 74.01 213.10 37.6 Reno, NV/USA 39.53 119.82 146.53 38.5 tan θ = sin γ San Francisco, CA/USA 37.46 122.25 142.19 39.1 cos(39.38°) − (6378 km) /(42,164 km) San Juan/Puerto Rico 18.48 66.13 242.07 48.8 = Seattle, WA/USA 47.60 122.33 147.34 30 sin(39.38°) Toronto/Canada 43.70 79.42 204.71 36.6 = 0.9799 Vancouver/Canada 49.22 123.10 147.10 28.3 Washington, DC/USA 38.53 77.02 210.99 40.7 θ = 44.42° 16 Satellite Engineering Research Corporation
  19. 19. Free space loss The free space loss takes into account that electromagnetic waves spread out into spherical wavefronts as they propagate through space due to diffraction. ⎛ 4π d ⎞ ⎛ 4π d f ⎞ 2 2 Ls = ⎜ ⎟ =⎜ ⎝ λ ⎠ ⎝ c ⎟ ⎠ ⎛ 4π d ⎞ ⎛ 4π d ⎞ 2 [ Ls ] = 10 log10 ⎜ = 20log10 ⎜ ⎝ λ ⎠ ⎟ ⎝ λ ⎟ ⎠ For a geostationary satellite, the free space loss is on the order of 200 dB (or a factor of 1020). The received power at the earth terminal is typically on the order of tens of picowatts. 17 Satellite Engineering Research Corporation
  20. 20. Example Problem: Determine the free space loss for a Ku band downlink between Telstar 5 at 97° W Longitude and Los Angeles if the frequency is 12 GHz and the angle of elevation is 44.4°. Solution: The wavelength is c 3 × 108 m/s λ= = = 0.025 m f 12 ×10 Hz 9 The slant range is d = r 2 − ( RE cosθ ) 2 − RE sin θ r = orbit radius = (42,164 km) 2 − (6378 km × cos 44.4°)2 − 6378 km × sin 44.4° RE = Earth’s radius θ = elevation angle = 37, 453 km Thus ⎛ 4π d ⎞ ⎛ 4π × 37, 453, 000 m ⎞ 2 2 Ls = ⎜ ⎟ =⎜ ⎟ = 3.544 × 1020 ⎝ λ ⎠ ⎝ 0.025 m ⎠ [ Ls ] = 10 log10 (3.544 × 1020 ) = 205.5 dB 18 Satellite Engineering Research Corporation
  21. 21. Received carrier power Received carrier power Ae P C= = Φ Ae S L Transmit gain Footprint area 4π 4π d 2 4π d 2 Gt = η * =η* S =η* ΩA S Gt Receive gain Receiver equivalent area 4π λ2 Gr = Ae Ae = Gr λ 2 4π Received carrier power Gr (λ 2 / 4π ) P 1 (Gt Pin ) Gr EIRP Gr C= = = 4π d 2 / Gt η * L (4π d / λ ) 2 L Ls L Equivalent isotropic radiated power Free space loss ⎛ 4π d ⎞ 2 EIRP = Gt P in Ls = ⎜ ⎟ ⎝ λ ⎠ 19 Satellite Engineering Research Corporation
  22. 22. Example Problem: Determine the received carrier power for the Ku band downlink between Telstar 5 and an Earth terminal in Los Angeles if the frequency is 12 GHz and the antenna has an efficiency of 0.60 and a diameter of 5.0 m. Allow a rain attenuation loss of 1.9 dB, a gaseous atmospheric loss of 0.1 dB, and a pointing loss of 0.2 dB. Solution: The satellite EIRP in Los Angeles is 49.2 dBW. At 12 GHz, the antenna gain is 53.7 dB and the free space loss is 205.5 dB. Therefore, the received carrier power is [C ] = [EIRP] + [Gr ] − [ Ls ] − [ Lr ] − [ La ] − [ L p ] = 49.2 dBW + 53.7 dB − 205.5 dB − 1.9 dB − 0.1 dB − 0.2 dB = −104.8 dBW Therefore, C = 10−10.48 W = 3.3 × 10−11 W = 33 pW 20 Satellite Engineering Research Corporation
  23. 23. Noise power Thermal noise power in bandwidth B N = N0 B = kB T B where the spectral noise density is N0 = kB T for system temperature T and Boltzmann’s constant is k B = 1.381×10−23 W / K Hz [k B ] = −228.6 dBW / K Hz 21 Satellite Engineering Research Corporation
  24. 24. Link budget equation Carrier power EIRP Gr C= Ls Lr Lo Noise power N = kB T B = N0 B Carrier to noise ratio C G 1 1 1 1 1 = EIRP N T Ls Lr Lo k B B Carrier to noise density ratio C C G 1 1 1 1 = B = EIRP N0 N T Ls Lr Lo k B 22 Satellite Engineering Research Corporation
  25. 25. Link budget equation (continued) The link budget equation is expressed in logarithmic (dB) form as follows (dB values indicated by brackets): Uplink [C / N 0 ] = [EIRP] + [G / T ] − [ Ls ] − [ Lr ] − [ Lo ] − [k B ] at satellite E/S satellite at uplink frequency Downlink [C / N 0 ] = [EIRP] + [G / T ] − [ Ls ] − [ Lr ] − [ Lo ] − [k B ] at E/S satellite E/S at downlink frequency 23 Satellite Engineering Research Corporation
  26. 26. Combined uplink and downlink Only thermal noise (Average White Gaussian Noise) −1 −1 −1 ⎛C⎞ ⎛C⎞ ⎛C⎞ ⎜ ⎟ =⎜ ⎟ +⎜ ⎟ (numeric) ⎝ N ⎠ net ⎝ N ⎠up ⎝ N ⎠ down Include interference −1 −1 −1 −1 ⎛C⎞ ⎛C⎞ ⎛C⎞ ⎛C⎞ ⎜ ⎟ = ⎜ ⎟ +⎜ ⎟ +⎜ ⎟ ⎝ N ⎠ net ⎝ N ⎠up ⎝ N ⎠ down ⎝ I ⎠ Noise power N = N0 B C C 1 = N N0 B 24 Satellite Engineering Research Corporation
  27. 27. Power flux density The EIRP of the uplink Earth station antenna must be adjusted to match an acceptable power flux density (PFD) at the satellite. EIRP 1 1 EIRP 1 1 PFD = Φ = = 4π d Lr L Ls (λ 2 / 4π ) Lr L 2 [Φ ] = [EIRP] − [4π d 2 ] − [ Lr ] − [ L] or [Φ ] = [EIRP] − [ Ls ] − [λ 2 / 4π ] − [ Lr ] − [ L] 25 Satellite Engineering Research Corporation
  28. 28. Example Problem: For an uplink between an Earth station in Washington, DC and Telstar 5, the EIRP is 79.0 dBW, the slant range is 37,722 km, the rain attenuation is 5.9 dB, and the antenna pointing loss is 0.2 dB. Determine the power flux density incident on the satellite. Solution: [Φ ] = [EIRP] − [4π d 2 ] − [ Lr ] − [ L] = 79.0 dBW − 10 log10 {4π (37,722,000 m) 2 } − 5.9 dB − 0.2 dB = −89.6 dBW / m 2 This PFD is within the specifications Saturation Flux Density - Typical CONUS for Telstar 5. -75 to -96 (dBW/m²) at Ku-band adjustable in 1 dB steps Ku-band Optional "Automatic Level Control" Mode Mitigates the effects of uplink rain fade by maintaining the transponder at a specific fixed operating point between saturation and 8 dB input backoff. 26 Satellite Engineering Research Corporation
  29. 29. Example link budget Signal architecture Satellite Information bit rate Mbps 22.5 Name Telstar 5 dBHz 73.5 Longitude deg 97.0 Modulation QPSK Transponder bandwidth MHz 27.0 Coding V(7,1/2) EIRP dBW 49.2 Bits per symbol 2 G/T dB/K 2.0 Code rate 1/2 Percentage of raised cosine filtering 20 Noise bandwidth MHz 22.5 Occupied bandwidth MHz 27.0 BER 0.00001 Eb/No (uncoded) dB 9.6 Coding gain dB 5.1 Eb/No (ideal) dB 4.5 Modem implementation loss dB 0.5 Eb/No (required) dB 5.0 C/No (required) dBHz 78.5 27 Satellite Engineering Research Corporation
  30. 30. Example link budget (continued) Uplink Earth station transmit terminal Link calculation Frequency GHz 14.0 City Washington Wavelength m 0.0214 Longitude deg 77.0 Earth station EIRP dBW 79.0 Latitude deg 38.5 Satellite G/T dB/K 2.0 Earth central angle deg 42.7 Free space loss dB 206.9 Elevation angle deg 40.8 Rain region D2 Slant range km 37722 Availability percent 99.95 HPA Power W 100.0 Rain attenuation dB 5.9 dBW 20.0 Antenna pointing error deg 0.02 Antenna diameter m 9.2 Antenna pointing loss dB 0.2 Antenna half power beamwidth deg 0.16 Boltzmann's constant dBW/K Hz -228.6 Antenna efficiency 0.55 C/No (uplink) dBHz 96.6 Antenna transmit gain dBW 60.0 Noise bandwidth dBHz 73.5 Line loss dB 1.0 C/N (uplink) dB 23.1 EIRP dBW 79.0 Power flux density dBW/m2 -89.6 28 Satellite Engineering Research Corporation
  31. 31. Example link budget (continued) Downlink Earth station receive terminal Link calculation Frequency GHz 12.0 City Los Angeles Wavelength m 0.025 Longitude deg 118.1 Satellite EIRP dBW 49.2 Latitude deg 34.0 Earth station G/T (clear sky) dB/K 32.0 Earth central angle deg 39.4 Free space loss dB 205.5 Elevation angle deg 44.4 Rain region F Slant range km 37453 Availability percent 99.95 Antenna diameter m 5.0 Rain attenuation dB 1.9 Antenna half power beamwidth deg 0.35 Degradation in G/T dB 2.2 Antenna efficiency 0.60 Gaseous atmospheric loss dB 0.1 Antenna receive gain dB 53.7 Antenna pointing error deg 0.05 Clear sky antenna noise temperature K 25 Antenna pointing loss dB 0.2 Receiver equivalent temperature K 125 Boltzmann's constant dBW/K Hz -228.6 System temperature K 150 C/No (downlink) dBHz 99.9 dBK 21.8 Noise bandwidth dBHz 73.5 G/T (clear sky) dB/K 32.0 C/N (downlink) dB 26.3 29 Satellite Engineering Research Corporation
  32. 32. Example link budget (continued) Combined uplink and downlink C/N (uplink) dB 23.1 C/N (downlink) dB 26.3 C/I (adjacent satellite) dB 20.0 C/I (cross polarization) dB 24.0 C/N (net) dB 16.7 Noise bandwidrh dBHz 73.5 C/No (net) dBHz 90.3 Information bit rate dBHz 73.5 Eb/No (available) dB 16.7 Eb/No (required) dB 5.0 C/No (required) dBHz 78.5 Margin dB 11.7 30 Satellite Engineering Research Corporation
  33. 33. Power levels in satellite link -30.0 dBW Output of modulator and upconverter Power Level 100 Uplink path (dBW) Earth Station 30.0 dB Driver gain EIRP = 79.0 72.9 Satellite 20.0 dB Earth station HPA gain EIRP = 49.2 1.0 dB Line loss 50 60.0 dB Earth station antenna gain 20.0 22.0 6.1 dB Rain attenuation + other losses 206.9 dB Free space loss 19.0 20.0 To From 0 0.0 Satellite demodulator modulator 30.0 dB Satellite receive antenna gain -30.0 -30.0 -35.0 69.0 dB Receiver amplifier gain Uplink Downlink 57.0 dB Satellite TWTA saturated gain -50 2.0 dB Output losses -65.0 29.2 dB Satellite transmit antenna gain Downlink path -100 -104.0 -104.8 205.5 dB Free space loss -105.0 2.2 dB Rain attenuation + other losses -134.0 53.7 dB Earth station antenna gain -150 0.2 dB Line loss -156.3 -158.5 40.0 dB LNA gain 35.0 dB Downconverter and IF amplifier gain Transmit Uplink Satellite Downlink Receive earth station path path terminal -30.0 dBW Input to demodulator 31 Satellite Engineering Research Corporation
  34. 34. α = half power beamwidth RF link (summary) λ = wavelength f = frequency c = speed of light Antenna half power beamwidth D = antenna diameter k = antenna taper factor λ c HPBW = α = k =k η*, η′, η = antenna efficiency factors D fD ΩA = antenna beam solid angle d = slant range Antenna gain S = footprint area 4π 4π 4π ⎛π D ⎞ 2 A = antenna area G =η * =η ′ =η 2 A =η ⎜ ⎟ C = carrier power ΩA Ω λ ⎝ λ ⎠ N0 = noise density Rb = information bit rate Free space loss Eb = energy per information bit ⎛ 4π d ⎞ ⎛ 4π d f ⎞ 2 2 EIRP = equivalent isotropic radiated power Ls = ⎜ ⎟ =⎜ ⎟ Gt = transmit antenna gain ⎝ λ ⎠ ⎝ c ⎠ Gr = receive antenna gain Pin = input power Carrier to noise density ratio Ls = free space loss L = net attenuative loss C E G G P EIRP (Gr / T ) = Rb b = t r in = T = system noise temperature N0 N0 Ls L k B T Ls L k B kB = Boltzmann’s constant 32 Satellite Engineering Research Corporation
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