ECE 4710: Lecture #41 1 Link Budget Example  Hughes Digital Satellite System (DSS)  Brandname is “DirecTV”  More than 220 TV channels  Two broadcast centers  Castle Rock, Colorado & Los Angeles, California »Baseband TV video signals are sampled, digitized, & compressed using MPEG (Motion Pictures Experts Group) standard  MPEG removes redundant image data within single frame and between frames  Data rate for one non-HD TV channel is ~3-6 Mbps depending on amount of motion in video, HDTV is ~8-15 Mbps »Broadcast all digital video data on 6 GHz carrier “uplink” to geostationary satellite transponders  QPSK Modulation

ECE 4710: Lecture #41 2 DirecTV Link Budget  Geostationary Satellite Transponders  Altitude = 22,242 miles above Earth  Located directly above equator at various longitudes »3 101° W longitude  DirecTV 1-R  W power  Core programming (ABC, NBC, CNN, TNN, MSNBC, etc.)  DBS-2 & DBS-3  W power  Local broadcast stations »1 110° W longitude w/ W  Local broadcast + Ethnic programming »1 119° W longitude w/ W  Local + Ethnic + HDTV

ECE 4710: Lecture #41 3 DirecTV Link Budget 6 GHz Uplink 12 GHz Downlink

ECE 4710: Lecture #41 4 Uplink / Downlink 6 GHz Uplink 12 GHz Downlink

ECE 4710: Lecture #41 5 DirecTV Link Budget  Satellite Transponder Processing  Filter + Amplify incoming uplink signal  Translate incoming uplink frequency to Tx signal downlink frequency »Shift ~6 GHz uplink signal to ~12 GHz  Up Conversion  Filter + High Power Tx Amplifier ( W)  Each transponder frequency has 24 MHz RF BW  Adjacent frequencies separated by 4 MHz guard BW »16 transponders on DirecTV 101° WL  16  24 MHz + 16  4 MHz = 448 MHz total BW »12.2 – 12.7 GHz satellite Tx frequency range for DirecTV 1-R satellite

ECE 4710: Lecture #41 6 DirecTV Transponder  51 dBW for Columbia, MO 6 GHz 12 GHz Up Converter

ECE 4710: Lecture #41 7 DirecTV Link Budget  Distance from satellite to Rx depends on lat/long  Slant range using law of cosines Earth Satellite Rh  R = Earth Radius = 3963 mi or 6378 km h = Satellite Height = 22,242 mi or 35,795 km R d

ECE 4710: Lecture #41 8 DirecTV Link Budget  Columbia, MO  38.9° N, 92.3° W  For core DirecTV 101° W Long  Elevation Angle ( E )

ECE 4710: Lecture #41 9 DirecTV Link Budget  Columbia, MO  Azimuth Angle ( A )  Rx Antenna Gain  DirecTV standard 18 inch (0.46 m) diameter satellite dish 12.2 – 12.7 GHz satellite Tx frequency range for DirecTV 1-R satellite  GHz is half-way point for f

ECE 4710: Lecture #41 10 DirectTV Antenna Temp  For Elevation Angle E = 44° and f ~ 12 GHz X T a ~ 20° K

ECE 4710: Lecture #41 11 DirecTV Home Rx ˜ Antenna Low Noise RF Amp Low Noise Block DownConverter G 1 = 40 dB & F 1 = 0.6 dB RG6/U Cable L = 8 dB / f IF = 950 – 1450 MHz IF FIlter IF AMP Demod / Detector F 3 = 10 dB TV IF Rx

ECE 4710: Lecture #41 12 DirectTV Home Rx  Rx System Noise Figure & Temperature  Assume 100 ft worst-case cable length so L 2 = F 2 = 8 dB  F s dominated by first stage  cable loss does NOT affect overall Rx system noise figure

ECE 4710: Lecture #41 13 DirectTV Home Rx  Rx System Noise Figure & Temperature  RF/IF Signal  Each transponder frequency has QPSK modulated signal with data rate R = 40 Mbps and signal BW = 24 MHz »Spectral efficiency  = 40 / 24 = 1.66 bps/Hz  corresponds to RC filtered QPSK with r = 0.20 »Each TV channel has data rate of 3-6 Mbps  8-10 non-HD channels on single transponder frequency

ECE 4710: Lecture #41 14 DirectTV Link Budget  Parameters from previous analysis  For Columbia, MO specifically  System parameters

ECE 4710: Lecture #41 15 DirectTV Link Budget  Link Budget Performance