Temperature Controlled Predistortion Circuits for 64 QAM Microwave Power Amplifiers

This report deals with the problem of nonlinearity characteristics in microwave power amplifiers for digital radio link systems with multi-level modulation (ex. 64 QAM); and in particular With reference to their degradations vs temperature variations. Moreover various possible methods of compensation are taken into account. After a brief examination of the not temperature controlled predistortion method operating at intermediate frequency, solutions are suggested to keep the non-linearity characteristics independent from thermal conditions. By presenting the experimental results and the comparative considerations, the use of the "feed-back controlled predistorter" and the "predictive method" is analysed.