DIGITAL PREDISTORTION LINEARIZER BASED ON VOLTERRA SERIES FOR NONLINEAR POWER AMPLIFIER
Keywords:
digital predistortion linearizer, nonlinear inertial power amplifier, Volterra series, intermodulation distortions, bit-error rateAbstract
Modern requirements for satellite communication systems for interference immunity and information transmission rate makes it necessary apply signals with complex modulation types and high spectral efficiency. As a rule, used digital signals described changeable amplitude, such as when rounding the modulating low frequency envelope fluctuations by Nyquist. For wideband transmission channels and so produce high requirements to ensure the path linearity with a large peak factor signal at the amplifier input, in particular for broadband transmitters and broadband power amplifiers. To carry out the linearization the characteristics of nonlinear power amplifier the most simple and effective technique is predistortion input. The problems linearization of static characteristics of nonlinear inertial power amplifier radio signal microwave frequency by using digital predistortion linearizer (DPD). DPD model is built based on Volterra series. To determine the DPD model coefficients author compiled overdetermined system of linear equations in the solution which minimize the squared deviations from the estimated solution. The analysis of the signal characteristics at the output of the nonlinear amplifier with linearizer, and bit error rate at the radio signal receiver with linearization of power amplifier characteristics. It is shown that the amplification of signal in the power amplifier with pre-linearization characteristics in DPD reduces power of combinational components and spectrum component of the output signal outside the main lobe, eliminating uncontrolled phase shift of signal, generated by the amplitude-phase inversion and also is achieved advantage in signal to noise ratio at the output of digital signal receiver demodulator. It is shown that by using DPD is possible to increase the energy efficiency of the data-transmission system by switching from the small-signal operating regime of the amplifier into the mode great power values of signal at the operating point at the power amplifier input. Method of research is analytical calculation and simulation.
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