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
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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