1038 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 58, NO. 4, APRIL 2010
Broadband Time-Domain Measurement System
for the Characterization of Nonlinear
Microwave Devices With Memory
Mouhamad Abouchahine, Alaa Saleh, Guillaume Neveux, Tibault Reveyrand,
Jean-Pierre Teyssier, Danielle Rousset, Denis Barataud, and Jean-Michel Nebus
Abstract—This paper describes a novel fully calibrated four
channel broadband time-domain measurement system for the
characterization of nonlinear microwave devices with memory.
The hardware architecture of the proposed time-domain measure-
ment system is based on a wideband sub-sampling principle. The
sampling heads work at a high strobe signal repetition frequency
that can be tuned between 357–536 MHz. We achieve a 40-GHz
RF frequency bandwidth and a 160-MHz IF bandwidth. This
instrument enables the measurement of carrier and envelope
waveforms at both ports of nonlinear microwave devices driven
by broadband modulated multicarriers. The test-bench is applied
to the cross modulation characterization of a 15-W GaN HEMT
CREE -band power amplifier with memory due to different
biasing circuit configurations. The amplifier under test is driven
by the sum of a large-signal modulated carrier (double-sideband
amplitude modulation at 3.6 GHz) and a small single-tone signal
at a 110-MHz offset frequency. Our significant contribution comes
from the capability of the measurement system to record the
time-domain waveforms of several nonadjacent modulated signals
on a similar time equivalent scale for different cases of memory
effects of the power amplifier under test.
Index Terms—Broadband sub-sampling, GaN power amplifiers,
memory effects, nonlinear microwave circuits, time-domain mea-
surements.
I. INTRODUCTION
W IDEBAND communication systems are increasinglyused to target multistandard multiband applications. In
these communication systems, various architecture design so-
lutions, as well as different modulation standards and multiple
access techniques can be implemented, as seen in [1] and [2].
In that context, the characterization of nonlinear devices such
as power amplifiers driven by multiple nonadjacent signals is of
interest.
Manuscript received June 18, 2009; revised December 20, 2009. First pub-
lished March 11, 2010; current version published April 14, 2010. This work was
performed in the context of the ELOPSYS cluster’s Lipsys Project supported by
the “Ministère de l’économie des finances et de l’emploi Direction Générale des
Entreprises” under Contract 06.2.93.0716.
The authors are with the XLIM Laboratory, UMR 6172, University
of Limoges, 87060 Limoges Cedex, France (e-mail: mouhamad.abou-
chahine@xlim.fr; alaa.saleh@xlim.fr; guillaume.neveux@xlim.fr; tibault.
reveyrand@xlim.fr; jean-pierre.teyssier@xlim.fr; danielle.rousset@xlim.fr;
denis.barataud@xlim.fr; jean-michel.nebus@unilim.fr).
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TMTT.2010.2042503
The work proposed in this paper focuses on wideband time-
domain measurement technique and setup based on the broad-
band harmonic sub-sampling principle.
Recently, different time-domain measurement systems have
been proposed to target the wideband characterization of non-
linear microwave devices. The need for a good tradeoff between
dynamic range and frequency bandwidth has led to the use of
microwave transition analyzers [3], digital storage oscilloscopes
[4], [5], or large-signal network analyzers [6], [7].
Large-signal network-analyzer measurements based on the
harmonic sub-sampling principle performed at 20 MHz have
demonstrated great interest for nonlinear microwave device
characterization. Nevertheless, significant complexity arises
when measurements of signals having envelope bandwidths
wider than 10 MHz are required. This is due to low-frequency
repetition rate of the strobe signal. Time-domain measurements
of wideband multisines requiring complex processing tech-
niques and specific control of the strobe frequency have been
proposed in [7] and [8]. The complexity of these techniques is
due to the hardware frequency limitation of sampling heads.
In [9], we proposed a new architecture based on the use
of sampling heads working with a high-repetition frequency
strobe signal (from 350 to 540 MHz) that enables wideband
time-domain measurements. 60-MHz bandwidth have been yet
performed and demonstrated in [9].
This paper presents an extended description of the main char-
acteristics of the broadband sampler based instrument, such as
gain conversion versus IF and RF frequencies. We report up
to 110-MHz envelope bandwidth measurements. We also focus
on time-domain envelope waveform measurements applied to
the characterization of a power amplifier exhibiting memory ef-
fects depending on its biasing circuit configuration. Additional
insights are mentioned to prove the capability of the setup to
perform simultaneous time-domain envelope waveforms at dif-
ferent carriers.
To conclude, we mention the potential use of the measure-
ment tool for behavioral modeling of wideband nonlinear de-
vices with memory.
II. DESCRIPTION OF THE MEASUREMENT SYSTEM
A. Hardware Configuration for Wideband Measurements
The proposed instrument is based on the harmonic sub-sam-
pling principle, which enables the downconversion of mi-
crowave spectra into IF spectra. The downconvertor is the key
component of the instrument.
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