Satellite uplink and downlink Analysis and Design Link-budget calculations are usually made using decibel or decilog quantities. Where no ambiguity arises regarding the units, the abbreviation dB is used. For example, Boltzmann’s constant is given as 228.6 dB, although, strictly speaking, this should be given as 228.6 decilogs relative to 1 J/K.

Equivalent Isotropic Radiated Power A key parameter in link-budget calculations is the equivalent isotropic radiated power, conventionally denoted as EIRP

A key parameter in link-budget calculations is the equivalent isotropic radiated power, conventionally denoted as EIRP. the maximum power flux density at some distance r from a transmitting antenna of gain G is

The [C/N0] ratio is then used in the link budget calculations The [C/N0] ratio is then used in the link budget calculations. A measure of the performance of a satellite link is the ratio of carrier power to noise power at the receiver input, and link-budget calculations are often concerned with determining this ratio. Conventionally, the ratio is denoted by C/N (or CNR), which is equivalent to PR/PN. In terms of decibels,

Earth Stations – antenna systems on or near earth Uplink – transmission from an earth station to a satellite Downlink – transmission from a satellite to an earth station Transponder – electronics in the satellite that convert uplink signals to downlink signals

UPLINK The uplink of a satellite circuit is the one in which the earth station is transmitting the signal and the satellite is receiving it. The free space loss and other losses which are frequency dependent are calculated for the uplink frequency. The resulting carrier to noise density ratio which appears at the satellite receiver.