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Solutions for

Characterizing and Designing
Linear/Nonlinear Active Devices
Accurately characterizing devices'
nonlinear behavior

Application Note

Overview Problem
With the proliferation of high data rate wire- The goal for R&D engineers and scientists
less communications, R&D engineers and working in the telecommunications industry
scientists are being challenged to research today is clear: efficiently and accurately
and design components and systems which simulate and design active components
provide voice, video, IP, and more in a (e.g., amplifiers and frequency doublers).
fast, compact, power-efficient format. This Accomplishing this goal requires accurate
requires pushing semiconductor devices to characterization of a device's linear and
their performance limits and, increasingly, nonlinear behavior, as well as an accurate
into their nonlinear regions of operation. and predictable simulation environment
Nonlinear device behavior can be especially covering this behavior. Traditionally,
problematic in the telecommunications interoperable solutions combining
industry, contributing significantly to modeling, simulation and measurement
information interference and a reduction have not been available for fully nonlinear
in effective bandwidth. Dealing with components and systems. Engineers rely
nonlinearity demands new measurement on limited S-parameter information and
methodologies that go far beyond today's are forced to perform extensive and costly
linear S-parameters which fail to provide empirical-based iteration of designs, adding
engineers with the capabilities to accurately substantial time and cost to the design
model, simulate and improve the design process. A new design methodology can
flow of new product technology. now make designing active devices and
components deterministic. By allowing
engineers to model, simulate and design
with significant reduction in design itera-
tions, it dramatically speeds time to market
for products with increased accuracy and
therefore better specifications.
A new design methodology from Agilent
Technologies, based on X-parameters,
X-parameter device models and nonlinear
vector network analyzer measurements,
enables fast and accurate characterization
and design of active devices and components.
X-parameters are a mathematically rigorous
superset of S-parameters, applicable to
nonlinear (as well as linear) components
under large and small signal conditions. They
enable the characterization and hierarchical
design of chains of nonlinear components
(e.g., multi-stage power amplifiers and multi-
chip modules) and RF systems (e.g., amplifiers
and mixers) which are commonly used in
communications applications. By measuring
X-parameters, R&D engineers and scientists
can accurately characterize and gain insight
into a device's nonlinear behavior.
FIGURE 1: Agilent's NVNA software, for use with the PNA-X microwave network analyzer,
Using Agilent's Nonlinear Vector Network establishes a new industry standard in RF nonlinear network analysis from 10 MHz to 50 GHz.
Analyzer (NVNA) -- based on Agilent's PNA-X
network analyzer technology -- X-parameters
can be quickly and accurately measured
(Figure 1). This information is then used
to create X-parameter models that can be
imported into Agilent's Advanced Design
System (ADS) simulator (Figure 2). Once
imported, these models are used to simulate
actual linear and nonlinear component
behavior. Together, the NVNA and ADS
simulator form an automated, interoperable
measurement and simulation system for
predictable design of nonlinear components.

X-parameters, ADS and the NVNA can be
used to reconstruct time domain waveforms,
optimize performance parameters such as
ACPR, EVM and PAE, design multi-stage
components and systems under varying
inter-stage match conditions, and optimize
nonlinear system performance. By providing FIGURE 2: Deterministically measure and view X-parameters with Agilent's NVNA and ADS.
a fast, accurate and powerful approach for
the design of active devices, these solutions
completely eliminate the need for limited
S-parameter information or costly, time
consuming design iterations. The time saved
can be much better spent designing the most
competitive products possible.


Handset Amplifier Example
Using the NVNA, X-parameters and the
ADS simulator, it is a straightforward
process to improve the performance
(PAE and output power) of an amplifier
being designed for use in a handset. The
process results in a significant reduction
in measurement test time and engineering
time, and saves substantial design costs.

X-parameters are first measured by the
NVNA and then modeled in ADS. Accurate
efficiency contours for PAE and output
power can then be simulated directly in
ADS from the X-parameter model (Figure
3). Inter-stage matching coefficients are
directly generated for optimization of the
component. By employing this method,
measurement test times and engineering
time are significantly reduced, and
substantial cost savings realized.

FIGURE 3: X-parameters give contours and waveforms at any loading condition including
cascaded systems.

Summary of Results
The Power of X
The inefficient, time-consuming and
expensive way of designing active devices The Agilent PNA-X Microwave Network
and components using limited S-parameter Analyzer with the NVNA software is a key
information is greatly improved by making product in Agilent's comprehensive Power
use of an interoperable measurement of X suite of test products. These products
and simulation environment for designing grant engineers the power to gain greater
nonlinear components. X-parameters help design insight, speed manufacturing
further simplify this design process by processes, solve tough measurement
providing an accurate representation of a problems, and get to market ahead of the
device's nonlinear (and linear) behavior. competition.
During simulation the device's linear/
nonlinear behavior can be fully optimized. Offering the best combination of speed
and scalability, and created and supported
by renowned worldwide measurement
experts, Agilent's X products are helping
engineers bring innovative, higherper-
forming products to emerging markets
around the globe.

To learn more about Agilent's suite of X
products please visit:

Related applications Remove all doubt www.agilent.com