Load Pull Simulation

Welcome

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Andy HowardSenior Applications Engineer Agilent EEsof

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Outline

• What is load pull and why do it?

• Working with measured load pull data – use to design matching networks

• Simulating load pull on nonlinear device models (including X-Parameters) – use to determine optimal source and load impedances

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Outline




A really simple load pull

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Device performance depends on source and load impedances

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Input match.network

Output match.network

freqf1 f2 f3

freqf1 f2 f3

Externalload (or next stage)

Externalsource (or previous stage)

Fundamental load pull setup

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freqf1 f2 f3

freqf1 f2 f3

Load tunerSource

tuner

Available source power constant

Why? Quick “sanity check”; adjust sampled area

Guess reasonablevalues for allvariables.Adjust, if necessary.

Fundamental load pull – with power sweep

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freqf1 f2 f3

freqf1 f2 f3

Load tunerSource

tuner

Available source power swept freq

Why? See gain compression and constant powerdelivered data

Fundamental source pull setup

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freqf1 f2 f3

freqf1 f2 f3

Load tuner

Source tuner


Why? Source impedances affect performances, too

Fundamental load pull with parameter sweep

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freqf1 f2 f3

freqf1 f2 f3

Load tunerSource

tuner


…

Sweep any parameter - source frequency, bias, etc.Why? Investigate device performancemore thoroughly

freq

Harmonic load phase sweep

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freqf1 f2 f3

freqf1 f2 f3

Load tunerSource

tuner

freq

Sweep input power to see constant powerdelivered data

Why? Harmonic impedancesmatter, but usually want highreflection

Source stimulus determines responses we may plot

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Gain comp.curves from source powersweep

IMD from2-tonesource

ACLR frommodulated source

Constant power delivered load pull with parameter sweep – more precise characterization

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freqf1 f2 f3

freqf1 f2 f3

Load tuner

Source tuner

Available source power optimized

…

Sweep any parameter - source frequency, bias, etc.

freq

Power deliveredheld constantvia optimization

Check sensitivity of completed design

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Input match.network

Output match.network

freqf1 f2 f3

freqf1 f2 f3

Loadtuner

Sourcetuner

Could be X-Parametermodel, instead

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Outline




You have measured load pull data (Maury)

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What’s the optimal load? What performance can we get from this device?

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Examine performance contours

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1) Reads LP data file2) Simulates S-parameters

of network3) Gets corresponding

performance data Tuner generates loads in region you specify

View independent variables and performance parameters

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Frequency andinput power constant

Plot performance contours of interest

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Load giving best performance

Using measured data containing a power sweep

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Sweep valueswithin rangeof those in file

Sweep based ongamma_x, gamma_yvalues in file

Why sweep power? See gain compression data.

Contours at specified gain compression

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Why do contours look strange? Measurements at some loads were not valid.

Contours at a particular input power

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From contours we decide optimal impedances. What’s next?

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Design impedance matching network(s) using existing techniques, or…

Use measured data directly in optimization

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This impedance should bethe same as this.

Optimized component values and corresponding reflection coefficient

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Outline




A sequence for running load pull simulations

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1) 1-tone, 1 input power load pull2) Add power sweep to see gain compression3) Run frequency or bias sweep4) Run harmonic load phase sweep5) Run constant output power with swept var6) Run source pull7) Use 2-tones to see IMD8) Use modulated signal to see ACLR

Based on experience:a) Change orderb) Delete stepsc) Iterate

Use of “instrument” subcircuits simplifies setup

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Most parameters are passed to tuner inside “instrument” subcircuit

Start with fast, simple load pull

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Source Power= 5 dBm

Source Power= 12 dBm

Refine sample space

• Available source power held constant• Guess optimal Zsource and harmonic Zs


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Load Pull with power sweep

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Interpolated data at 30 dBm output power

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Loads for maximum PAE and minimum gain compression

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Contours at X-dB gain compression

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Adjusting contour lines to all pass through maximum PAE load

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Maximum PAE (Perf1 marker) occurs with 28.8 dBm power delivered (Perf3 contour) and 12.3 dB gain(Perf2 contour.)


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Contours versus swept parameter (frequency)

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28 dBm contour at 750 MHz

28 dBm contour at 1.25 GHz


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Dependency on phase of gamma at harmonic(s)

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Also sweeping gate bias

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Controlling output powerenables more precise analysis

Contours with gate bias = 1.5 V

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High PAE, but low gain

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Results with gate bias = 2.25 V

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Constant power delivered load pull with two tones

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Load pull with WCDMA signal

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Read modulated data from file. Scale signal amplitude by optimizing “SFexp” variable.

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Review

• Basic load pull concepts

• Using measured load pull data files to design matching networks

• Fast, simple load pull

• Adding power sweeps to see compression

• Sweeping frequency

• Sweeping harmonic reflection coefficient phase

• Constant power-delivered load pull with sweep

• Using two tones to see intermodulation distortion

• Load pull with a WCDMA source

For more information:

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http://edocs.soco.agilent.com/display/eesofkc/Load+Pull+DesignGuide+Enhancements+for+post+ADS+2011_05

On the latest release of ADS:

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On the latest release of the ADS Load Pull DesignGuide:

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© Agilent Technologies, Inc. 2011Published in USA, November 8, 20115990-9506EN

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Load Pull Simulation