Cyril Descleves
Mentor Graphics

This technical paper shows how Eldo RF can be used to perform spectral regrowth analysis, a complex effect occurring when RF circuit blocks (typically power amplifiers) are driven with digitally modulated signals. The standard measure of the spectral regrowth effect is the ACPR (Adjacent Channel Power Ratio).

The ACPR measurement uses the 'modulated steady-state' analysis feature of Eldo RF, which allows efficient simulation of realistic digitally modulated signals. ACPR is rather difficult to estimate with two-tone tests. Indeed, using two-tone simple steady-state simulations requires crude approximations, and the reliability of the ACPR estimations obtained through these methods is questionable.

Using the modulated steady-state analysis with realistic digitally modulated signals is a much more accurate method to estimate ACPR.

This document describes how to set up the simulations to analyze a power amplifier, extract its gain and S parameters, determine its large-signal behavior (compression), and finally estimate its ACPR. Ready-to-run netlists are provided with the application note to illustrate the simulations.