What are X-Parameters?

Agilent NVNA and
X-Parameter Simulation
in ADS
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X-Parameters Enable Model
Generation from Simulation or
Measurement for Fast
Development
Measuring Nonlinearities for Use Directly in Design
Wouldn’t it be nice if you could measure and display the full amplitude and
phase information of each spectral component?
Wouldn’t it be even nicer to then use it directly in ADS harmonic balance or
circuit envelope simulation or Ptolemy system simulator?
A1,P1
A2,P2
A1,P1
2
A3,P3
F1
F1
F2
F3
in
out
out
out
What are X-Parameters?
X-parameters are the mathematically correct superset of Sparameters, applicable to both large-signal and small-signal
conditions, for linear and nonlinear components.
The math exists!
We can measure, model, & simulate with X-parameters. Each
part of the puzzle has been created The pieces now fit together
seamlessly.
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Nonlinear Vector Network Analyzer (NVNA)
The new industry standard for nonlinear measurements
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X-Parameters Come from the Poly-Harmonic
Distortion (PHD) Framework
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X-Parameter Concept:
Approxs. to NL Mapping
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Results: Design of Cascade vs. Measurement of
Cascade
“X-parameters enable predictive nonlinear design from NL data”
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X-Parameters: Why They are Critical
Predict performance of cascaded NL components
*
Be , f = X ef( F ) (| A11 |) P f + ∑ X ef( S,g)h ( A11 ) P f − h ⋅ Agh + ∑ X ef(T,g)h ( A11 ) P f + h ⋅ Agh
g ,h
g ,h
P = e jϕ ( A11 )
“New” Terms!
Cascaded Nonlinear Amplifiers:
Nonlinear effects of mismatch
versus drive
• Unambiguously identifiable (simple, automated extraction) from automated set of
measurements
• Fully nonlinear vector quantities (Magnitude and phase of all harmonics)
• Extremely accurate for high-frequency, distributed nonlinear circuits
• Cascadable (correct behavior in mismatched environment)
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Black-Box Characterization & Behavioral Modeling
Measurement-Based Model
Actual Amp Circuit
• Circuit models don’t exist
• Completely protect design IP
Generate
Behavioral
Model
Design of Module or
Instrument Front End
Detailed Circuit Model
(SPICE/ADS) of IC
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PHD Framework: Simulating with Measured Data
Once measured, the X-parameters can
be immediately used for design in ADS.
Agilent PHD Code
NVNA Application
Take X-parameter
measurements
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Memory
Interface
Extract X-parameters
Export model file
Works in HB and Envelope,
Not in Transient
Example: X-Parameters Verification
Amplifier component
models from individual
measured X-parameters
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Results Cascaded Simulation vs. Measurement
“X-parameters enable predictive nonlinear design from NL data”
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Third Order Intercept Simulation
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Input / Output Spectrums & ACPR
Spectral Re-growth
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PA Linearization using X-Parameters in ADS Digital
Pre-Distortion Linearization Design Guide
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Summary
• X-parameters are a mathematically correct superset of S-parameters for
nonlinear devices under large-signal conditions.
• X-parameters (for two-port devices under large-signal excitation from a
single large input tone in this offering) can be accurately measured by
automated set of experiments on the new Agilent NVNA instrument.
• Together with the PHD Framework, measured X-parameters can be used
in ADS to design nonlinear circuits.
• All pieces of the puzzle are available and they fit together!
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