Agilent 5992-0137EN Solutions for Implementing Envelope Tracking in Power Amplifiers - Application Note c201 free download

File name 5992-0137EN Solutions for Implementing Envelope Tracking in Power Amplifiers - Application Note c201

Keysight Technologies Solutions for Implementing Envelope Tracking in Power Amplifiers Application Note 02 | Keysight | Solutions for Implementing Envelope Tracking in Power Amplifiers - Application Note Fast and Efficient Configuration and Test of Envelope Tracking Systems--From R&D to Design Verification and Into Production--Using a Range of Flexible and Accurate Hardware and Software Solutions Overview By their very nature, Power Amplifiers (PAs) are power hungry, nonlinear devices. They are also a critical component in modern mobile communication devices like smartphones and tablets, which hold increased battery capacity and power efficiency at a premium. PA techniques like Crest Factor Reduction (CFR), Digital Pre-Distortion (DPD) and Envelope Tracking (ET) were introduced as a way to overcome these issues, while at the same time reducing problems associated with distortion and nonlinearity. ET offers significant advantages in terms of improved battery life and RF PA perfor- mance, along with reduced heat dissipation. Also, it's an increasingly important capability for PAs that support high peak/average modulation schemes. With smartphones and tablets increasingly employing wider bandwidths, Multi-Input Multi-Output (MIMO) technology, and higher order Orthogonal Frequency Division Multiplexing (OFDM) modulation formats to achieve higher data rates, the use of ET is projected to become even more critical. Problem While a PA operating in ET mode does exhibit greater power efficiency and better performance, these benefits come at the price of complexity. And it's this complexity that makes configuring and testing an ET system so challenging. Consider a basic ET system block diagram as shown in Figure 1. Here, the envelope detector gener- ates the envelope by taking the magnitude of the IQ waveform and then applying a shaping table to determine the actual voltage supplied to the PA. Next, a shaped envelope is supplied to the Envelope Tracking Power Supply (ETPS), which modulates the Vcc so that the bias voltage tracks changes to the RF input waveform. Finally, the PA outputs the amplified RF signal. Unlike polar modulation, ET does not apply a level limiter or operate with a fixed amplitude PA input signal. Instead, it uses a mixture of open and closed loop feedback, with delays introduced to the IQ or RF path to match those in the supply modulation path. In an open loop system, the shaping curve is applied to the envelope signal to match the supply voltage versus RF gain in the PA. Pre-distortion may also be used. DC Power Envelope Shaping Vin Envelope tracking detector table power supply |X| (LUT) (ETPS)