Power amplifier characterization: an active load-pull system based on six-port reflectometer using complex modulated carrier

Abstract

An original measurement system for nonlinear RF power-transistor characterization is presented. This new setup enables measurement and optimization of output power, power added efficiency (PAE) or linearity using active fundamental tuning and six-port reflectometers as vector network analyzers. High and low frequency bias-Tees are inserted at both ports of transistors in order to control source and load impedances at the base-band (envelope) frequency. Experimental results at 1.575 GHz, show an ACPR improvement of 20 dB for a commercial GaAs MESFET power transistor.

An active load-pull setup for broadband signals using digital baseband processing for the active loop

“…This phase deviation as well as the frequency response around the carrier frequency (typically not considered in other work [5]) further contributes to an accuracy degradation of EVM and ACPR measurements. Hence, a way has to be found for compensating the time delay and frequency response.…”

“…If broadband signals are used in active load pull systems, only closed loop systems can be used [5]. Open loop systems like [6] provide inaccurate results because of using an undistorted signal as the reflected wave for a nonlinear amplifier (the error is only small when using undistorted signals for the harmonic zones [7]).…”