In-flight adaptive pre-distortion techniques for ttc subsystems with high-order modulations - expro plus

Future near-Earth F-class and M-class SCI missions will require high-rate links in X-Band, for either maximizing the data return or decreasing the ground station usage (especially in case of 35-m DSN antennas). Clear examples are THESEUS and HAYDN that are targetting 15-20 Mbps and, forachieving this, their TTC subsystems will need to resort to high-order modulations that fully exploit the 10 MHz X-Band allocation.ESA already performed several activities for the development of X-Band transponders and ground stations receivers that can support the high-order modulations foreseen in the standard CCSDS 131.2, known also as SCCC.However, the performance of these modulations is highly impaired by the nonlinear effects of the X-Band power amplifier, the TWTA or SSPA. For tackling this, currently, transponders adopt predistortion algorithms based on a training performed on ground that uses as reference the power amplifier nonlinear characteristic measured at beginning of life. On the other hand, the aging of components makes the nonlinear characteristic changing overtime, thus diminishing the benefits of predistortion along the lifetime of the satellite missions.For tackling this, in-flight adaptive pre-distortion techniques, able to track the nonlinear variations over time, becomes mandatory. Thus, this activity will first study and define possible techniques that can be adopted in TTC subsystem of SCI missions, by defining the changes to be performed in the transponder digital board, and its interface with the power amplifier. Then, a HW breadboard will be implemented as proof of concept.