A.O. Pergushev – Assistant, 

Higher School of Applied Physics and Space Technologies of Peter The Great St. Petersburg Polytechnic University E-mail: pergushev.aleksey@mail.ru

V.A. Sorotsky – Dr.Sc.(Eng.), Professor, 

Higher School of Applied Physics and Space Technologies of Peter The Great St. Petersburg Polytechnic University E-mail: sorotsky@mail.spbstu.ru

A.M. Ulanov – Ph.D.(Eng.), Associate Professor, 

Higher School of Applied Physics and Space Technologies of Peter The Great St. Petersburg Polytechnic University E-mail: ulan-bator-1955@mail.ru

Amplification of signals with a high peak-to-average power ratio is accompanied by a decreasing of the RF power amplifiers efficiency. To overcome this disadvantage, either envelope tracking method or Kahn envelope elimination and restoration technique can be used. In both cases, a tracking power supply (TPS) is used, the output voltage of which changes in accordance with the law of the radio frequency signal envelope. To increase the efficiency the TPS it contains a switched mode power amplifier that gains the envelope in the pulsewidth modulation mode. Due to nonlinear voltage transformations caused by the switched mode, envelope distortions inevitably appear in the output voltage of the TPS, which can lead to a noticeable deterioration in the radio frequency signal spectrum.

Their level can be evaluated via simulation. However, due to the excessive complexity of such models, the simulation time for a single calculation can reach up to several hours. This significantly complicates the research of the TPS characteristics, and it makes almost impossible to take into account the statistical dispersion of the TPS elements' parameters. Reducing simulation time can be achieved by using the analytical model. The objective of the paper is to develop an analytical model that allows to take into account the influence of factors that can affect the distortion of the TPS output voltage, and to work out measures enabling to reduce them. In this case, the analytical model should provide a calculation error acceptable in engineering practice and be highly efficient in terms of simulation time. The proposed analytical model provides an error as much as 10% in comparison with the results of simulation, whereas the simulation time can be reduced by 5…8 times. Based on the research results, recommendations are formulated on the choice of the electronic components and the forming TPS control signals, which will enable reducing by 10…30 dB the level of spurious harmonics in the spectrum of the TPS output voltage.

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