Page 416 - Satellite Communications, Fourth Edition

396 Chapter Twelve

12.28. For an uplink the required [C/N] ratio is 20 dB. The operating frequency
1
is 30 GHz, and the bandwidth is 72 MHz. The satellite [G/T] is 14.5 dBK .
Assuming operation with 11 dB input BO, calculate the saturation flux density.
[RFL] are 1 dB.

12.29. For the uplink in Prob. 12.28, the total losses amount to 218 dB.
Calculate the earth station [EIRP] required.

12.30. An earth station radiates an [EIRP] of 54 dBW at 14 GHz from a 10-m
parabolic antenna. The transmit feeder losses between the HPA and the antenna
are 2.5 dB. Calculate the output of the HPA.

12.31. The following parameters apply to a satellite downlink: saturation
[EIRP] 22.5 dBW, free-space loss 195 dB, other losses and margins 1.5 dB, earth
station [G/T] 37.5 dB/K. Calculate the [C/N 0 ] at the earth station. Assuming an
output BO of 6 dB is applied, what is the new value of [C/N 0 ]?
12.32. The output from a satellite TWTA is 10 W. This is fed to a 1.2-m parabolic
antenna operating at 12 GHz, the feeder loss being 2 dB. Calculate the [EIRP].
12.33. The [C/N] values for a satellite circuit are uplink 25 dB, downlink 15 dB.
Calculate the overall [C/N] value.

12.34. The required [C/N] value at the ground station receiver is 22 dB and
the downlink [C/N] is 24 dB. What is the minimum value of [C/N] that the
uplink can have in order that the overall value can be achieved?

12.35. A satellite circuit has the following parameters:

Uplink, decilogs Downlink, decilogs
[EIRP] 54 34
[G/T] 0 17
[FSL] 200 198
[RFL] 2 2
[AA] 0.5 0.5
[AML] 0.5 0.5
Calculate the overall [C/N 0 ] value.

12.36. Explain how intermodulation noise originates in a satellite link, and
describe how it may be reduced. In a satellite circuit the carrier-to-noise ratios
are uplink 25 dB; downlink 20 dB; intermodulation 13 dB. Calculate the overall
carrier-to-noise ratio.

12.37. For the satellite circuit of Prob. 12.36, input BO is introduced that
reduces the carrier-to-noise ratios by the following amounts: uplink 7 dB,
downlink 2 dB, and improves the intermodulation by 11 dB. Calculate the new
value of overall carrier-to-noise ratio.