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Direct Digital Predistortion on a Computer Controlled FPGA

We report on the development of direct digital radio frequency predistortion techniques for high power amplifiers and their demonstration in a MF band FPGA-based system. The basic component of our work is a nonlinear cubic voltage characteristic which is realized digitally by means of a look-up table. This method is situated in the context of existing baseband and analog predistortion techniques. In particular, we demonstrate our results experimentally and show a relationship between the bit-depth of our look-up table and the size of intermodulation distortions in the output of a class A amplifier.