Overview of modern load-pull Overview of modern load-pull and other non-linear and other non-linear

measurement systemsmeasurement systems

ARFTG Nonlinear Measurements WorkshopARFTG Nonlinear Measurements Workshop

San Diego, November 2001San Diego, November 2001

Andrea Ferrero

Dipartimento di ElettronicaPolitecnico di Torino, Italy

ARFTG –2001 – San Diego 2

Basics of load-pull

Load-pull Controlling the loading condition at the output port

Source-pull Controlling the loading condition at the input port

Fundamental load-pull Controlling the loading/source condition at the

fundamental frequency

Harmonic load-pull Controlling the loading condition at one or more

harmonic frequencies

Definitions

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Basics of load-pull

Example of load-pull data

Output power [dBm] @ 1dB gain compression

Power Added Efficiency (PAE) [%]

@ 2dB gain compression

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Basics of load-pull

Power meter or scalar analyzer-based only scalar information on DUT performances economic

Vector receiver (ANA, 6-port) vectorial and more complete informations on DUT

performances high accuracy, thanks to vector calibration expensive

Time Domain Receiver (MTA-NVNA) Waveform capabilities Complexity, high cost

Measurement systems

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Passive load-pull systems

Passive loads Mechanical tuners Electronic tuners (PIN diode-based)

PowerMeter

PowerSensor

PowerSensor

and power sensors Passive tuners

S L

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Passive load-pull

Features Single or double slug tuners High repeatability of tuner positions Pre-characterization with a network analyzer High power handling

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Passive Load Pull

Slab LineMotors

DUT

TUNERS

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Passive Limits

Drawback Load reflection coefficient limited in magnitude

by tuner and test-set losses This is true especially for harmonic tuning

higher frequency optimum load on the edge of the Smith chart

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PreMatchingPre-matching

To reach higher gamma while characterizing highly mismatched transistors Pre-matching networks Pre-matched tuners

L

LOSSL

LOSS L

Features Highest gamma attainable Difficult pre-calibration (5D space!!) Harmonic Loading uncontrolled

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PreMatching

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SWITCHING NETWORK

PORT 2

Real Time load-pull

Vector network analyzer-based system

NETWORK ANALYZER

DUT

InputLoad

OutputLoad

VECTOR INFO

NORMAL VNA CAL

ACTIVE LOADS

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Active load

Active loop technique

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Harmonic Load Pull

Controlling the Load/Source condition at harmonic frequencies

Waveshaping techniques at microwave frequencies

Great complexity of the system but potential improvement of the performance

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Passive load-pull

Passive Harmonic system

A Tuner for each harmonic Complex Easy to change frequency More control of the harmonic

load

Harmonic Resonators Difficult to change frequency Only Phase control of the

load

f0

2f0

FundamentalHarmonic

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Harmonic active load-pull

Extending the active loop technique

Politecnico di Torino System

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Harmonic active load-pull

Extending the active loop technique

IRCOM Active Harmonic Load Pull

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4 Loops Harmonic system

VNA

Switching Unit

Couplers

Amplifier

Loop Unit

DUT and Probe

Maury/Paf Active Harmonic Load Pull

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SWITCHING NETWORK

Test Signal

Time domain load-pull

Transition Analyzer based system

MTA TD WAVEFORMS

DUT

InputLoad

OutputLoad

VECTORAND TD INFO

TD CAL REQUIRED

ACTIVE LOADS

Ref Signal

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Calibration and Verfication

Passive System Coaxial VNA Measurement of the Tuners for different

positions (typically thousands) De-embedding of external components (probe,cables ..)

Real Time Active System Standard Measurements directly at the reference plane Error Model as ordinary S-parameters

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Load-pull Accuracy

Reference plane definitions

VNA-based system: calibration

t

Thru

Line

Short

Short

Load

Open

PwrMeter

DUT

1

in

2

L

3

SWITCHING NETWORK

NETWORK ANALYZER

Probe Tip

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Main Contributions to Power Waves Calibration Residual UncertaintyNWA measurement repeatability (0.1 %)Uncertainty on power calibration

coefficient (input TWTA during calibration: 2%, no TWTA 0.5%)

On-wafer probe position repeatability (0.2%)

Uncertainty

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Passive LP System

tuner position repeatability S-parameter measurement uncertainty:

residual NWA calibration uncertainty NWA repeatability

measured power uncertainty (power meter dynamic range)

Main Contributions to Uncertainty

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Comparison Passive vs. Active

Output Power Standard Uncertainty

• passive LP: red line

• active LP

0.086

0.17

0.25

0.34

0.4

0.5

dBm

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Classical PA design Information like: Power Sweep Optimum Loads

MAP based designAdditional info with Active Real Time

System GammaIn AM/PM conversion

Harmonic Load conditionTime Domain Info

Load Pull and PA Design

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DATA SET EXAMPLE

Load Pull and PA Design

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Power Sweep and more

Power Sweep @ Best Load for Pout

-70.00

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

10.00

20.00

30.00

27.5526.7525.4423.6021.6019.5817.7115.9614.3112.74

Pav (dBm)

dB

/ d

Bm

40.00

42.00

44.00

46.00

48.00

50.00

52.00

54.00

56.00

58.00

60.00

Pout

Gain

IM3L

IM3R

AM/PM

Eff

GammaL= 0.41 , 167 Frequency= 18 GHz

1dB Compression

1dB compression PointPout=26.29 dBmGain= 9.72dBIM3R= -18.34 dBcIM3L=-18.50dBc

Eff=48.07 %

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Load Pull and PA Design

OUTPUT POWER @ 1 dB GAIN COMPRESSION

POWER GAIN@ 1 dB GAIN COMPRESSION

COMBINING LP MAP INFORMATIONTO OPTIMIZE POWER PERFORMANCES

26dBm

12dB

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PAE @ 1 dB GAIN

COMPRESSION

C/I 3 LEFT @ POUT = 24 dBm

COMBINING LP MAP INFORMATION TO OPTIMIZE LINEARITY PERFORMANCES

50% -28dBm

Load Pull and PA Design

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Harmonic Information

Harmonic Load Effect on Efficiency

Power Added Efficiency (PAE) [%] @ 4 GHz, 2dB gain compression

as a function of the second harmonic load value (8 GHz).

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Time Domain LP

Waveform check

Istantaneous Working Point

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Conclusions

Load-pull test set as important tools for: Power amplifier design Model Verification Device optimization

Different possibility available according to Testing needs Application needs Budget

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Many Thanks to

Dave Hartskeerl - Philips Research Laboratories

Surinder Bali – Maury Microwave