Abstract
A method to predict intermodulation (IM) products of two tone test based on Amplitude to amplitude (AM-AM) and amplitude to phase (AM-PM) diagrams of power amplifier is proposed in this paper. An RF power amplifier is mathe-matically modeled by a power series in order of 13. Coefficients of the transfer function are obtained by odd-order polynomial fitting of the transfer function of the power amplifier that is modeled by power series, with AM-AM and AM-PM diagrams. Because of considering AM-PM distortion, coefficients have become complex. By using this transfer function, analytical expressions of IM products are derived. Frequency effect of IM products are modeled in suggested method to estimate the effects of changing in input frequency on output. With the mean of this factor the model is able to predict IM products of wideband frequency input. Simulated results agree well with the predicted method in comparisons.
Highlights
In modern communication systems, digital communication schemes, such as code division multiple access, where the information is carried are admitted by various systems
A method to predict intermodulation (IM) products of two tone test based on Amplitude to amplitude (AM-AM) and amplitude to phase (AM-PM) diagrams of power amplifier is proposed in this paper
Coefficients of the transfer function are obtained by odd-order polynomial fitting of the transfer function of the power amplifier that is modeled by power series, with AM-AM and AM-PM diagrams
Summary
Digital communication schemes, such as code division multiple access, where the information is carried are admitted by various systems. The power amplifier is the major source of nonlinearity in a communication system To increase their efficiency, power amplifiers are sometimes driven into their nonlinear region [1], causing spectral regrowth, increasing bit error rate, interference to adjacent channel, and intermodulation products to be generated. Similar previous models only used AM-AM diagram to characterize power amplifier’s transfer functions [3,8,9,10,11] while such an effect is considered in [7,1215] In this case, transfer function’s coefficients have become complex and this increases the difficulty of the calculations, but neglecting the AM-PM distortion causes many problems in predicting output spectrum [16,17,18]. With the mean of this method we can analyze power amplifier systems in the case that their circuit is not reachable
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