A simple and reliable technique to characterize amplitude to phase modulation distortion for high-frequency amplifiers and nonlinear devices

Abstract

This paper presents a simple and reliable measurement system for characterizing the amplitude to phase modulation (AM-PM) characteristics of high frequency amplifiers and nonlinear devices. The AM-PM measurement system is based on a null detector implemented with a double balanced mixer, and requires a voltmeter and a calibrated phase shifter. A 12 W class A radio frequency power amplifier has been designed using a GaN transistor, and the AM-PM has been measured using both the method proposed in this work and the classical method with a calibrated vector network analyzer. A good correlation between both methods is observed, which validates the proposed method.

FPGA-based test bed for measurement of AM/AM and AM/PM distortion and modeling memory effects in RF PAs

“…In this section, three AM/AM and AM/PM measurement techniques are described: the traditional measurement technique based on VNA [22], a simple and reliable test bed to measure the amplitude-to-phase conversion, and an alternative as a low-cost technique with PCs used as DSPs. As an additional technique, we propose a system at the emulation level that can implement the PA behavior in an FPGA board if the distortion curve data are available, as well as add a PA as a DUT.…”

“…2. This traditional technique mainly uses a microwave signal source, a power splitter, a calibrated phase shifter, and a double-balanced mixer, as reported in [11,22]. The reference signal S DOWN propagates through the calibrated phase shifter, referred to as the reference signal.…”

“…Some studies have used traditional measurement techniques such as the use of a vector network analyzer (VNA) [20] or a typical spectrum analyzer [21], a technique to characterize the AM/PM distortion for RF PAs and nonlinear devices [11,22], or the use of scalar power measurements of the PA [23]. More recently, in addition to calculating the PA's distortion curves [24,25], the works in [26][27][28] have used personal computers (PCs) as digital signal processors (DSPs) to reduce the cost of measurements.…”