Reduction of Higher Harmonics in the Signal Spectrum in Switched Mode Amplifiers Using Predistortions Generated by a Neural Network

Abstract

In recent years, there has been a tendency to reduce heat dissipation from various kinds of technical devices including radio transmitters. To reduce heat dissipation in radio transmitters, switched mode power amplifiers (PAs) can be used, the efficiency of which is as high as 95-98%. However, the high level of higher harmonics is a problem of such PAs. To reduce them to the required value, a staged voltage can be used. In this case, attention must be paid to the angle coordinates of the voltage stages. It is shown that even their insignificant deviations caused by different values of the transistor parameters significantly increase the level of higher harmonics. To solve this problem, a predistortion of control pulses should be implemented using a neural network. The results of experiments confirm the possibility to reduce the level of the 2nd, 3rd, 5th and 7th harmonics in a three-stage voltage by 30…40 dB to the required level of minus 60 dB.