Analysis of different optimization criteria for IF predistortion in digital radio links with nonlinear amplifiers

A compensation technique for nonlinearities is usually necessary in QAM digital satellite links. Analog waveform compensation has the advantage of reducing out-of-band spectral emissions with respect to end-to-end digital predistortion, in addition to its easy realization. Nevertheless, it has been often neglected in the literature because of its lack of adaptivity; we propose making the predistorter fully adaptive. Different control schemes applied to fifth-order IF predistortion with different optimization criteria have been investigated. A simulation-based analysis shows that adaptive IF compensation achieves excellent performance if compared with static predistortion of the same order. Comparisons with upper bounds related to digital predistortion with memory, moreover, denote that IF analog predistortion can be truly considered an alternative approach, especially for narrow pulse shaping.