Agilent 5991-1463EN Simulating Envelope Tracking with Advanced Design System Software - Application Note c20 free download

File name 5991-1463EN Simulating Envelope Tracking with Advanced Design System Software - Application Note c20

Simulating Envelope Tracking with Keysight Advanced Design System Application Note 1.0 Introduction Modern modulated signals often have high peak-to-average One way to bolster low efficiency in the back-off region is power ratios (PAPR). Use of such high PAPR signals results to use Envelope Tracking (ET), a technique that allows the in power amplifiers (PAs) having to operate at a large amplifier's drain bias to track the magnitude of the input back-off when stringent linearity requirements must be signal envelope. When the input signal envelope is low, the satisfied. Operating a PA at relatively high output power drain bias can be reduced so the amplifier operates closer back-off ensures the signal is not greatly distorted when its to its optimal efficiency point. envelope excursion is near its peak. However, the greater the amount of back-off, the lower the PA's efficiency. If we could dynamically adjust the drain bias to lower values when the input signal is lower, we can operate the A power amplifier with a fixed drain bias may have high power amplifier at a higher level of efficiency (Param1 is power-added efficiency (PAE), but only at a high output the drain bias), as shown if Figure 2. power (the red trace in Figure 1.) The power amplifier with the PAE-versus-output power characteristic shown in this More information about Envelope Tracking is available at: figure would have to be operated in back off (thus with low www.open-et.org PAE) to avoid distorting the signal. Table of Contents 1.0 Introduction ... i 2.0 Characterizing the Power Amplifier ... 4 3.0 Examining the Modulated RF Signal ...10 4.0 Simulating the Power Amplifier with a Fixed Drain Bias ...13 5.0 Implementing Envelope Tracking Using Behavioral Model Components ...14 6.0 Using Ptolemy Sources and Sinks to Simulate EVM and Drain Efficiency ...16 7.0 Using the 89600 VSA Software to Display Results ...22 8.0 Modeling Effects That Influence Distortion ...23 9.0 Summary ... Back cover Figure 1. This power amplifier must be operated in back off (where PAE is lo