Development Environment for EER and Envelope Tracking RF transmitters

Abstract

Power amplifier (PA) efficiency is a criticalfactor in any portable device. Two ofthe most popular architectures to improve the efficiency, envelope tracking (ET) and envelope elimination and restoration (EER), are discussed in this paper. A test systemfor characterization ofsuch a system is presented. A Class E based EER system is tested and characterized and software corrections are implemented to linearize the transmitter Test results show an ACPR improvement of 15 dB by only tuning the phase signalk amplitude and adding AM/PM correction. EVM improves from 2.8% to 0. 71% at the same time.

Comparison of static and memory predistortion in envelope tracking system

“…The AWG hardware [1] consists of 1) The FPGA part implemented on Xilinx Virtex-II-1000, 2) The interface to controlling PC and 3) converter and filter board. The IQ modulator is a Texas instruments model TRF3701, which is used to upconvert the baseband signal to 1GHz.…”

“…This paper is a further study of a well-documented (ET) and (EER) transmitter environment [1]- [3]. The environment is built around data sequencer implemented on a Xilinx Virtex-II FPGA and the following test setups has been published:…”

“…• Class E based EER with polynomial AM-AM and AM-PM predistortion for 0.5MHz signals [1] • Class AB based ET with polynomial AM-AM and AM-PM for 1MHz signals [2] • Class AB based ET for 1MHz signals with emphasis on different envelope modulation schemes (i.e. V DD -drives) [3] In [3], ET transmitter with linear 0.5W 1GHz LDMOS power amplifier with constant compression envelope yielded drain efficiency of 41% and power added efficiency of ca.…”

Bias relationships for Envelope Tracking technique

“…In fact, for input power level lower than 5dBm the assumption of constant g m value is not yet verified. Moreover the dependence of the drain-source capacitance (C ds ) by the drain bias voltage (V DD (x)) would cause a variation of the output load during the dynamic [5].…”

Envelope tracking power amplifier with static predistortion linearization

“…The power supply is modulated from 0 to 6 V with a linearly assisted switcher with a modulation bandwidth of 6 MHz, presented in more detail in [10]. A programmable DSP signal generator [11] provides modulated carrier and envelope signals. Section 2 discusses the design methods and constraints of the implemented amplifier and Section 3 provides the results achieved with different driving techniques.…”