Calculation of the suppression of signals and intermodulation noise when multiple unequal carriers are amplified by a TWT

Weak signals are suppressed and intermodulation noise is generated when a number of carriers having different amplitudes are amplified by a TWT. These effects are analyzed using an extension of a method which has been described previously² and which is simpler to use than other methods in current use^4,5,6,7. This paper describes the calculations and includes a comparison of the results with experimental observations. The results are useful in the design of a satellite communications system in which a TV signal and multiple radio or two-way voice signals are present in one satellite transponder. The calculations show that for each 1 dB signal suppression of the small carriers due to the presence of a large carrier at saturation, the suppression of intermodulation noise is by more than 2 dB. Based on these results, it would be advantageous to operate with a single carrier saturating the transponder when multiple unequal carriers are present.