31 0 65KB
Exercises 1. A satellite link operating at 14GHz has receiver feeder losses of 1.5 dB and a free space loss of 207dB.The atmospheric absorption loss is 0.5dB, and the antenna pointing loss is 0.5dB. Depolarization losses may be neglected. Calculate the total link loss for clear sky conditions. 2. An e a rt h station transmits at 8GHz from an antenna of 3.5m. The transmitter generates an output of 18kW. The satellite is 3990 km from the earth station; satellite gain of 30 dB. The efficiency of the transmitting antenna being 0.66. Calculate: Path loss, Transmitting antenna gain, ERIP, received power at satellite, Improvement in a received power if the satellite uses parabolic dish of 2.5m. Considering your calculated results, suggest, as a designer, how you could reduce the transmitter power while maintaining the same level of received power. 3. A geostationary satellite is receiving -100dBW (frequency of 5GHz) from an earth station. If power transmitted is 100KW from a 10m antenna. Calculate efficiency of the transmitter and suggest a design to reduce the power transmitted keeping same level of power received. 4. In a satellite communications link, the uplink carrier to noise ratio (C/N)U is 20 dB whereas the downlink carrier to noise ratio (C/N)D is 25 dB. Find the total link carrier to noise ratio.G_T = 45 dB 5. Find the system temperature for a satellite system which is having an antenna temperature (TA) = 50K, Gain of RF amplifer (Grf) = 200 and temperature of RF amplifer Trf = 50K, temperature of mixer (Tm) = 500K, temperature of IF Amplifer (Tif) =1000K and gain of Mixer (Gm) =0.1. G_if= 150 6. A direct broadcast satellite-TV with two earth stations, is composed of an uplink and downlink with the following parameters (as shown in the setup in Figure below) Pt =160 W, Gt = 34.3 dB Receiving terminal Gr = 33.5 dB. Downlink path loss = 205.7 dB Antenna beam loss = 3.0 dB Other losses = 0.4 dB Clear air atmospheric loss = 0.4 dB. Noise power budget in the earth station receiver are as follows: Ts = 145 K Bn = 20 MHz Boltzmann constant k = 1.38 x 10-23 J/K
Frequency: 6 GHz and distance 10,000 km
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Calculate the received power at the earthstation. What is the carrier-to-noise- ratio of the downlink (C/N) d ?
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What should be the uplink carrier-to-noise- ratio (C/N) u to get a minimum permitted overall ratio (C/N)o = 14.25 dB? 8. In a link budget calculation at 12 GHz, the free space loss is 206 dB, the APL is 1 dB, AA is 2 dB. The receiver G/T is 19.5 dB/K and RFL is 1 dB. EIRP is 48dBW. Calculate the carrier to noise spectral density ratio. 9. An uplink of 14 GHz, and flux density required to saturate the transponder is -120 dB(W/m 2). The free space path loss is 207 dB, the other spatial losses amounts to 2 dB. Calculate the earthstation EIRP required for saturation, assuming clear sky conditions. 10. An uplink at 14 GHz requires a saturation flux density of -91.4 dB W/m 2 and input backoff of 11 dB. The satellite [G/T]= -6.7 dB/K and the RFL is 0.6 dB/ fnd the carrier to noise power spectral density ratio. (ans: 74.53 dB)