TABLE OF CONTENTS The link budget uses the noise and LNA along with the signal level to determine the range and quality of the satellite link. To calculate the signal or carrier level at the input to the receiver, an effective isotropic radiated power EIRP is determined from the transmitter.
The EIRP out of the transmitting antenna is power output of the power amplifier PA, losses from the PA through the antenna, and the gain of the antenna. The power out of the PA is usually expressed in dBw, 10 log (watts).
Several types of PAs are used for transmitting signals to the satellite. They include traveling wave tubes (TWTs), Klystrons, and low-cost field effect transistor (FETs) amplifiers. TWTs offer wide bandwidths, up to 500 MHz and higher, good group delay, and the ability to handle many signal inputs. The Klystrons are expensive, high-power only PAs with narrow bandwidths around the 40 to 80 MHz range. The FET solid state (SS) amplifiers offer low-cost solutions and include many of the features that the other technologies offer, though generally not for extremely high power outputs. A general power requirement for different types of signals include 1 watt per channel for telephone signals and 1 kilowatt per television carrier.
The losses are negative (in dB) and are added to the PA output power. The antenna gain is added to the final result (in dB). Some of the losses that could be included...
