Reliable Prediction of Intermodulation Interference and Crosstalk in Nonlinear Satellite Transponders

The prediction of multicarrier performance in nonlinear satellite transponders is essential for optimizing a communication system providing frequency division multiple access (FDMA) operation. In general satellite nonlinearity is determined by the traveling wave tube amplifier (TWTA) used as power stage. A suitable mathematical tool for TWTA performance computation is the quadrature model, which is shortly described. Numerical results obtained with this model being in excellent agreement with measurements are used as basis for evaluation of intermodulation and crosstalk effects in satellite transponders. Partially new results are presented covering the following aspects: optimization of multicarrier operation point under uplink fading, spectrum spreading in multicarrier operation, suppression of single-tone and noiselike interference and cascading of amplifiers.