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Understanding the SystemVue To
ADS Simulation Bridge
Application Note
Introduction
Agilent SystemVue is a new system- Coded baseband Closed-loop feedback for Coded baseband
level design environment that enables reference IP BER, HARQ, throughput reference IP
a top-down, model-based design
methodology for both communication Source SystemVue SystemVue Receiver
I/O I/O
physical layer (PHY) systems and
aerospace/defense systems.
This application note examines the
link from SystemVue directly into a ADS RF/IF ADS
I/O Designs I/O
RF hardware design flow that allows
RF nonlinear physical
mutual system-RF co-verification. design with layout/EM
At a practical level, this is achieved
by adding special I/O blocks that Figure 1. SystemVue can drive ADS in a live co-simulation to achieve higher system-level
connect dataflow simulators in both accuracy and enable more predictive collaboration.
SystemVue 2010.01 and Agilent
Advanced Design System (ADS) Benefits for both baseband/DSP and RF designers
2009 Update 1. This connection
allows a complex-valued, sampled This completed round trip allows system-level architects and baseband algo-
I/Q datastream from SystemVue to rithm developers to benefit from the increased accuracy for analog-domain
flow to ADS where it can be pro- components and RF "work-in-progress." Typically, these users of math, C++,
cessed with the Circuit Envelope or and HDL language modelling do not have access to high-accuracy, envelope-
Transient/Convolution circuit simula- domain physical models. Instead, they do their development in isolation with
tor and then return to SystemVue inferior RF equivalents.
for coded receiver and demodulation
(Figure 1). RF circuit designers also derive a benefit from the completed round trip. Their
early RF designs can be seen operating in a working system with early baseband
DSP processing wrapped around them, using realistic waveforms. While ADS
users are accustomed to co-verifying baseband designs with their RF circuits, in
most situations, the baseband DSP has already been completed. Consequently,
there is no real opportunity to change the DSP, only to verify the RF. RF design
groups can now access earlier baseband investigations (in the math or C++
stages), before they are committed to implementation and while there is still
time to re-partition the system design between either the baseband or RF
paths--the best place to solve a problem, if one should occur.
In essence, SystemVue allows cross-domain debugging (down to the math or
C++ algorithms) in order to track and solve architectural issues that were
previously difficult to do across toolsets.
Indirect alternatives to live co-simulation
In this application note we will look Coded baseband Closed-loop feedback for Coded baseband
at a live co-simulation between reference IP BER, HARQ, throughput reference IP
SystemVue and ADS. However, there
are indirect alternatives to this con- Source RF/IF Receiver
Model
figuration that have other advantages.
They are briefly discussed here, for a
more complete perspective.
Represent the RF in a friendly way to Baseband DSP, X-param,
so the system-level can go fast, with improved accuracy DPD, other
SystemVue can export active base-
band models and file-based I/Q wave-
forms to ADS, for use natively within
the ADS environment. Similarly, ADS ADS simulations RF/IF
can export X-parameters* and static PNA-X measurements Designs
RF nonlinear physical
I/Q waveforms back to SystemVue. design with layout/EM
These exported objects are easier to
use, run orders of magnitude faster in Figure 2. SystemVue and ADS can both export models to each other's environments,
the target environment (with control- allowing faster, offline simulations tailored to that environment.
lable accuracy trade-offs), and allow
separate simulations to be done Live co-simulation, the subject of this application note, allows both baseband
offline across different computers, and RF design to be used directly in their native environments, with no addi-
organizations, license pools, and tional translation or model extraction steps. While the resulting simulations
intellectual property domains are often slower, they enable the full functionality, libraries and accuracy of the
(Figure 2). original environments to be used. For example, the ADS Circuit Envelope simula-
tor supports memory and dynamic biasing effects that are not typically included
in behavioral models, and can also include the full 3D EM accuracy of the
physical amplifier design. Another benefit is that the live simulation connection
makes it convenient to cross-check and debug partially-completed designs (that
is, use them "as-is"), saving considerable troubleshooting and verification effort
at later stages of integration.
SystemVue-ADS co-simulation: two cases
Two application cases are shown
SystemVue
below. The first case shows a direct
link between the SystemVue dataflow
simulator, and the dataflow simulator
in ADS ("ADS Ptolemy"), shown in
Figure 3. This link allows for re-use
of signal processing schematics
and behavioral models that an ADS
user may already have created.
Additionally, it enables ADS users ADS
to take advantage of newer libraries
and capabilities of the SystemVue
platform.
Figure 3. Shown here is the SystemVue to ADS Ptolemy co-simulation link.
2
The second application case goes
SystemVue
one step further (Figure 4). It shows
the same link from SystemVue to
ADS Ptolemy, but here ADS Ptolemy
also performs its own system-circuit
co-simulation inside ADS, linking
to either the Circuit Envelope or
Transient/Convolution simulation
engines. By connecting SystemVue
to a real physical simulation,
system-level designers can improve
the accuracy of the RF PHY for their
algorithmic studies (e.g., for digital
pre-distortion). ADS users can take
advantage of higher SystemVue
capabilities, such as closed-loop
ADS (Circuits) ADS (Ptolemy)
LTE "throughput" measurements, by
embedding their RF in active HARQ Figure 4. System designers who already own ADS Ptolemy can perform cross-domain,
feedback channels. line-by-line debug of their C++ and math algorithms in SystemVue while connected to
active RF, carrier/envelope-level memory effects in ADS. This cannot be done without
the two Agilent platforms, shown above.
Configuration
The ADS-SystemVue co-simulation
link discussed here requires files and
examples that are not included with
the commercial releases of either
SystemVue 2010.01 or ADS 2009
Update 1. To download and install
these files, supported customers are
invited to visit the Agilent EEsof EDA
Knowledge Center technical support
website at (http://edocs.soco.
agilent.com/x/YoFvBg).
Installation steps
Figure 5. The ADS co-simulation palette