IMS2011 in Baltimore: A Perfect Match
IMS2011
Power Amplifier Design Utilizing the
NVNA and X-parameters
Loren Betts1, Dylan T. Bespalko2, Slim
Boumaiza2
1Agilent
Technologies, Santa Rosa CA, USA
2University of Waterloo, Waterloo ON, Canada
IMS2011 in Baltimore: A Perfect Match
Presentation Outline
Amplifier Design Considerations using X-parameters
• Industry Challenges
• Introduction to X-parameters
End-to-End Power Amplifier Design with X-parameters
• Load-Dependent X-parameters
• High Power X-parameter Measurement Configuration
• Final PA Results
IMS2011 in Baltimore: A Perfect Match
Next Generation Communication Systems
Power Amplifier Industry Challenges:
• Research & development of new semiconductor processes for
next generation components
• Develop smaller, higher power, more efficient active device
designs
• Reduce cost and the development time to bring product to
market
Issues:
• Components are exhibiting more & more nonlinear behavior
(often by design to increase efficiency)
• Models of newer technologies (such as GaN) may not exist or
may not provide an accurate description of all the component
behavior.
IMS2011 in Baltimore: A Perfect Match
How do I optimize desired Amplifier
Specifications?
Ant
PAE (accuracy<3%)
Vcc
Icc
Zo=50ohm
Matching
Network
Matching
Network
ACPR
(accuracy<1dB)
2W max
VSWR=2.5 max
PAE= Power Added Efficiency
ACPR= Adjacent Channel Power Ratio
VSWR= Voltage Standing Wave Ratio
IMS2011 in Baltimore: A Perfect Match
Evolution of the Tools & Measurements
Patchwork
S-Parameters
TOOLS:
SS & Oscilloscope
Grease pens and
Polaroid cameras
Slotted line
Power meter
MEASUREMENTS:
Bode plots
Gain
SWR
Scalar network analyzers
Y & Z parameters
TOOLS:
Vector Network
Analyzer
MEASUREMENTS:
Gain
Input match
Output match
Isolation
Transconductance
Input capacitance
S-Parameters +
Figures of Merit
NVNA
X-Parameters
TOOLS:
NA
SA/SS/NFA
Power meter
Oscilloscope
DC Parametric Analyzer
MEASUREMENTS:
Gain compression, IP3, IMD
PAE, ACPR, AM-PM, BER
Constellation Diagram, EVM
GD, NF, Spectral Re-growth
ACLR, Hot “S22”
Source and Load-Pull
IMS2011 in Baltimore: A Perfect Match
S-parameters:
Linear Measurement, Modeling & Simulation
Measure with linear VNA:
Small amplitude sinusoids
a1
S 21
Incident
S 11
Reflected
Transmitted
Linear Simulation:
Matrix Multiplication
S-parameters
b1 = S11a1 + S12a2
b2 = S21a1 + S22a2
b2
DUT
Port 2
Port 1
b1
Transmitted
S 12
S 22
Reflected
Incident
a2
Model
Parameters:
Simple algebra
bi
Sij =
aj
ak = 0
k≠ j
IMS2011 in Baltimore: A Perfect Match
S-parameter Measurements
y (t )
x(t )
a10
e110
e111
e100
b10
a11
e101
S11
b11
a12
b20
e200
e11
2
S 22
S12
e201
b21
S 21
e10
2
a20
bi = ∑ Sik ⋅ ak
k
=
b1 S11a1 + S12 a2
=
b2 S 21a1 + S 22 a2
 b1   S11
b  =  S
 2   21
S12   a1 
S 22   a2 
S-Parameter Definition
To solve, VNA’s traditionally use a
forward and reverse sweep (2 port
error correction).
IMS2011 in Baltimore: A Perfect Match
S-parameter Measurements
If the S-parameters change versus
drive direction then by definition
the resulting computation of the Sparameters becomes invalid
 b1   S11
b  =  S
 2   21
 b fwd
 1
 b fwd
 2
 S
 11
 S21

b1rev   S11
=
rev 
 S
b2
  21
S12
S22
  b fwd
= 1
  b2fwd
 
rev
1
b
b2rev
  a fwd
 1
  a fwd
 2
a1rev 

rev 
a2

rev
1
a
a2rev




y (t )
This is often why customers are
asking for Hot S22 because the
match is changing versus input
drive power and frequency
(Nonlinear phenomena).
S12   a1 
S 22   a2 
S12   a1fwd

S22   a2fwd

x(t )
−1
This still does not provide the
complete picture. X-parameters
are the solution.
IMS2011 in Baltimore: A Perfect Match
X-parameters
X-parameters are the mathematically correct extension of Sparameters to large-signal conditions.
Measurement and simulation based, device independent, identifiable from a simple
set of automated NVNA measurements or directly from ADS circuit-level designs
Fully nonlinear (Magnitude and phase of distortion)
Cascadable (correct behavior in even highly mismatched environment)
Extremely accurate for high-frequency, distributed nonlinear devices
Measure X-parameters
-orGenerate X-parameters from
circuit-level designs
X-parameter Component
Simulate using X-parameters
ADS, SystemVue & Genesys
Design using X-parameters
IMS2011 in Baltimore: A Perfect Match
X-parameters
A1
A2
B1k = F1k ( DC , A11 , A12 ,..., A21 , A22 ,...)
B2 k = F2 k ( DC , A11 , A12 ,..., A21 , A22 ,...)
Harmonic (or carrier) Index
Port Index
B1
B2
Unifies
S-parameters
Load-Pull,
Time-domain
load-pull
The X-parameters provide a mathematically correct mapping of the ‘A’ and
‘B’ waves at ports, input powers, harmonics, DC bias, etc, etc.
IMS2011 in Baltimore: A Perfect Match
Scattering Parameters
S-Parameters – Linear System Description
=
b1 S11a1 + S12 a2
bi = ∑ Sik ⋅ ak
=
b2 S 21a1 + S 22 a2
k
X-Parameters – Linear and Nonlinear System Description
bij
X ij( F ) ( A11 ) P j +
∑ (X
k ,l ≠ (1,1)
(S )
ij , kl
( A11 ) P j −l ⋅ akl + X ij(T,kl) ( A11 ) P j +l ⋅ akl* )
A11 = Large signal drive to the amplifier input port (port #1) at the fundamental frequency (#1)
Definitions
i = output port index
j = output frequency index
k = input port index
l = input frequency index
For example:
Means:
T
X21,21
output port = 2
output frequency = 1 (fundamental)
input port = 2
input frequency = 1 (fundamental)
IMS2011 in Baltimore: A Perfect Match
NVNA and X-parameters
Measure X-parameters with
Agilent’s NVNA
Design with measured
X-parameters in ADS
Design and simulate with
measured or generated Xparameters in ADS
IMS2011 in Baltimore: A Perfect Match
Presentation Outline
Amplifier Design Considerations using X-parameters
• Industry Challenges
• Introduction to X-parameters
End-to-End Power Amplifier Design with X-parameters
• Load-Dependent X-parameters
• High Power X-parameter Measurement Configuration
• Final PA Results
IMS2011 in Baltimore: A Perfect Match
Load-Dependent X-parameters
Some components (un-matched transistors) may require input and output
tuners because their match is far from 50 ohm.
This may require an X-parameter model that also includes dependence an
arbitrary fundamental frequency load impedance supplied to the output of
the component. This is accomplished by adding an impedance tuner.
Depending on the component, and the class of operation, a multi-harmonic
tuner may not be required.
The source tuner can be fixed at a single impedance that is close to the
conjugate match point and a power sweep performed to vary the
available power to the component (i.e. No source pull required).
X-Parameter definition with port 2 gamma dependence
bij = X ij( F ) ( DC, A11 , Γ 2 ) P j +
∑
k ,l ≠ (1,1)
(X
(S )
ij , kl
*
( DC, A11 , Γ 2 ) P j − l ⋅ akl + X ij(T, kl) ( DC, A11 , Γ 2 ) P j + l ⋅ akl
)
IMS2011 in Baltimore: A Perfect Match
Load-Dependent X-parameter
Measurements
A11 is swept through
a power sweep
Γ 2 is swept through
a set of fundamental
frequency impedances
supplied by tuner. All other
harmonic impedances
are uncontrolled
Γ1, fixed
Γ2
IMS2011 in Baltimore: A Perfect Match
Power Amplifier Design
Goal:
Design a power amplifier
using X-parameter measurements
of a transistor.
Desired Design Goals:
Frequency = 1.2 GHz
Output power > 45 dBm
PAE > 60%
Class AB
X-parameter model measured
of a Cree CGH40045F GaN
transistor using NVNA.
Linearity and other performance parameters
were not part of this first phase design.
IMS2011 in Baltimore: A Perfect Match
Power Amplifier Design
Total PA design completed in ADS:
1. Simulated impedance contours of output power and
PAE at fundamental and harmonic frequencies at input
(gate) and output(drain) ports.
2. Simulated impedance contours used to determine
appropriate termination impedances at fundamental and
harmonic frequencies at input (gate) and output(drain)
ports to maximize PAE and output power
3. PCB designed with appropriate matching from (2)
4. Final PA assembled and compared against simulation
IMS2011 in Baltimore: A Perfect Match
NVNA X-parameter System – Power
Budget (120 W)
Couplers minicircuits ZGDC10362HP+
CF ~ -10 dB
Pmax >+ 53 dBm
-18 dBm to +2 dBm (DT)
-18 dBm (ET)
Maury Microwave
Port 1
+10 dBm to +32 dBm
Tuner
Bias
2x20 dB
(< 1 W)
AR 5S1G4
G = 30 dB at lowest gain
Pmax = +37 dBm (5 Watts)
Frequency = .8 – 4.2 GHz
R1
A
-20 dBm
NVNA
+12 dBm (ET) at +32
dBm input
10 dB (<
1 W)
AR 60S1G4
G = max 38 dB min 33 dB at
0%
Pmax = +48 dBm (60 Watts)
Frequency = .8 – 4.2 GHz
30 dB
-20 dBm
-20 dBm
R3
Cree CGH40045F GaN HEMT
F = 1.2 GHz
Gain ~ 12-16 dB
Pout ~ 46 dBm
-20 dBm
C
20 dB
+36 dBm
+36 dBm
+46 dBm (max)
2x20 dB (<
1 W)
40 dB
(10 W)
+26 dBm (ET)
Tuner
Port 2
10 dB (100 Watt)
1 dBm (ET) at G=35 dB
External HW
DUT
Couplers minicircuits ZGDC10362HP+
CF ~ -10 dB
Pmax >+ 53 dBm
Bias
Maury Microwave
IMS2011 in Baltimore: A Perfect Match
High Power X-parameter Measurement
System
IMS2011 in Baltimore: A Perfect Match
Model Verification
Verification of the measured X-parameter model:
1. Make measurements of component (transistor). These are not
X-parameter measurements but instead measurements of other
parameters like ‘A’ and ‘B’ waves, output power, PAE or another
parameter of your choice.
2. Record the input power, impedances (input and output ports,
fundamental and harmonic) and bias used during the
measurements in (1).
3. Place these impedances in the simulator as terminations of the
X-parameter model and sweep power over that used in
measurement range.
IMS2011 in Baltimore: A Perfect Match
X-parameter Model Verification - Circuit
Template
IMS2011 in Baltimore: A Perfect Match
X-parameter Model Verification - Results
Verification of X-parameter Model
2.0
Measured
Simulated
Drain Current (Amps)
Delivered Power (dBm)
46
44
42
40
0.7
38
20
22
24
26
Incident Power (dBm)
28
30
IMS2011 in Baltimore: A Perfect Match
Simulated Fundamental Pout and PAE
Contours
Maximum
Power
and contour
levels, dBm:
Power_contours
PAE_contours
46.05
E
P
46.00
45.50
45.00
44.50
44.00
43.50
43.00
42.50
Maximum PAE
and contour
levels, %:
70.812
E
level=70.711610, number=65
Output Power > 45 dBm
68.000
64.000
60.000
56.000
P
52.000
level=46.029871, number=52 48.000
44.000
40.000
PAE > 70 %
IMS2011 in Baltimore: A Perfect Match
Simulated Parameters
ADS Amplifier DesignGuide
Output Spectrum, dBm
50
19
0
18
m1Transducer Power Gain, dB
Gain Compression
between markers, dB
3.220
17
-50
m2
16
-100
45.70
15
38
-150
39
40
41
42
44
45
46
70
1.6
60
1.4
1.2
50
1.0
40
0.8
30
0.6
38
4.00G
3.50G
3.00G
2.50G
2.00G
1.50G
1.00G
500.M
0.000
1.200 GHz
30.0
29.0
28.0
27.0
26.0
25.0
24.0
23.0
22.0
21.0
20.0
20.000
21.000
22.000
23.000
24.000
25.000
26.000
27.000
28.000
29.000
30.000
RFpower[0,::]
Input and Output Voltage Waveforms
39
40
41
42
43
44
45
46
38
39
Fund. Output Power, dBm
Available
Source Power
dBm
Fundamental
Frequency
m3
Fundamental
Output Power
dBm
38.916
39.826
40.717
41.596
42.460
43.318
44.122
44.775
45.180
45.472
45.696
Transducer
Power Gain
18.916
18.826
18.717
18.596
18.460
18.318
18.122
17.775
17.180
16.472
15.696
Power- Added
Efficiency, %
37.953
42.019
46.465
51.376
56.108
61.767
67.226
71.322
72.659
73.308
74.317
DC Power
Consumpt.
Watts
20.281
22.583
25.069
27.747
30.984
34.283
37.877
41.453
44.579
47.124
48.783
40
41
42
43
50
30
45
20
40
10
35
0
-10
-20
High
Supply
Current
0.724
0.807
0.895
0.991
1.107
1.225
1.353
1.481
1.592
1.683
1.743
Thermal
Dissipation
Watts
12.547
13.047
13.361
13.415
13.500
12.977
12.242
11.653
11.865
12.142
11.988
30
25
20
-30
15
0.2
0.4
0.6
0.8
1.0
time, nsec
1.2
1.4
1.6
1.8
10
20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0
RFpower
44
Fund. Output Power, dBm
Fundamental and Third Harm., dBm
40
Spectrum[2]
Spectrum[3]
Spectrum[1]
ts(Vload), V
ts(Vinput), V
43
High Supply Current
1.8
Fund. Output Power, dBm
RF Power Selector
-40
0.0
Output Power
at Marker m2, dBm
PAE, %
80
45
46
IMS2011 in Baltimore: A Perfect Match
Final Power Amplifier
PAE could be improved based on
a better physical termination
impedance at the 2nd harmonic
at the input. However, there is a
tradeoff between the bandwidth
of the impedance and PAE.
Courtesy University of Waterloo
IMS2011 in Baltimore: A Perfect Match
X-parameter technology is expanding
rapidly
X-parameter breakthroughs:
• Load-dependent X-parameters
• 50 GHz Agilent NVNA
• High-Power X-parameters
• X-parameter generator in ADS
• Simulation of XnP component in ADS,
Genesys & SystemVue
• Two-tone measured X-parameters
• Three-port measured X-parameters
(mixers/converters)
• Memory: Dynamic X-parameters
• Education, training, app. Notes
IMS2011 in Baltimore: A Perfect Match
Thank You to Supporting Partners
•
•
•
•
•
AR RF/Microwave
Instrumentation
Cree
Maury Microwave
Mini-Circuits
University of
Waterloo
Thank You
IMS2011 in Baltimore: A Perfect Match
Appendix
IMS2011 in Baltimore: A Perfect Match
X-parameter Measurements
“Rules-of-Thumb”
Leave enough pre-amplifier linear gain for extraction and drive tones
If the pre-amplifier is saturated with the drive signal then adding the extraction
signal will degrade X-parameters. Generally seen during a power sweep
where there is divergence between simulated and measured results at the
higher end of the power sweep (watch receiver compression though).
Simulation termination impedance
When comparing simulated a’s and b’s from X-parameters against measured a’s
and b’s it is critical that the terminations in the simulation match that used
during measurement. Ensure proper calibration and de-embedding
techniques where applicable.
Calibration procedure using 8 term error model, tuners and preamplifiers
Often pre-amplifiers are removed behind the couplers during calibration and
then placed back in-line after the calibration procedure is complete. This may
effect the tuner characterization and therefore the source and load
impedances behind the tuners should be determined from the NVNA and
accounted for to ensure proper applied impedance to the component by the
tuners.
IMS2011 in Baltimore: A Perfect Match
For More Information
X-parameters
www.agilent.com/find/x-parameters
Nonlinear Vector Network Analyzer
www.agilent.com/find/nvna
ADS MMIC design seminar (click on X-parameters link)
www.agilent.com/find/eesof-mmic-seminar
X-Parameters Aid MMIC Design
http://www.mwrf.com/Articles/Index.cfm?Ad=1&Article
ID=22811
X-Parameter YouTube Videos
http://www.youtube.com/user/AgilentEEsof
Trademark Usage, Open Documentation &
Partnerships
http://www.agilent.com/find/x-parameters-info
IMS2011 in Baltimore: A Perfect Match
Selected References and Links
1.
D. E. Root, J. Horn, L. Betts, C. Gillease, J. Verspecht, “X-parameters: The new paradigm for measurement, modeling, and
design of nonlinear RF and microwave components,” Microwave Engineering Europe, December 2008 pp 16-21.
http://www.nxtbook.com/nxtbooks/cmp/mwee1208/#/16
2. D. E. Root, “X-parameters: Commercial implementations of the latest technology enable mainstream applications” Microwave
Journal, Sept. 2009, http://www.mwjournal.com/search/ExpertAdvice.asp?HH_ID=RES_200&SearchWord=root
3. J. Verspecht and D. E. Root, “Poly-Harmonic Distortion Modeling,” in IEEE Microwave Theory and Techniques Microwave
Magazine, June, 2006.
4. D . E. Root, J. Verspecht, D. Sharrit, J. Wood, and A. Cognata, “Broad-Band, Poly-Harmonic Distortion (PHD) Behavioral Models
from Fast Automated Simulations and Large-Signal Vectorial Network Measurements,” IEEE Transactions on Microwave Theory
and Techniques Vol. 53. No. 11, November, 2005 pp. 3656-3664
5. J. Verspecht, J. Horn, L. Betts, D. Gunyan, R. Pollard, C. Gillease, D. E. Root, “Extension of X-parameters to include long-term
dynamic memory effects,” IEEE MTT-S International Microwave Symposium Digest, 2009. pp 741-744, June, 2009
6. J. Verspecht, J. Horn, D. E. Root “A Simplified Extension of X-parameters to Describe Memory Effects for Wideband Modulated
Signals,” Proceedings of the 75th IEEE MTT-S ARFTG Conference, May, 2010
7. J. Xu, J. Horn, M. Iwamoto, D. E. Root, “Large-signal FET Model with Multiple Time Scale Dynamics from Nonlinear Vector
Network Analyzer Data,” IEEE MTT-S International Microwave Symposium Digest, May, 2010.
8. J. Horn, S. Woodington, R. Saini, J. Benedikt, P. J. Tasker, and D. E. Root; “Harmonic Load-Tuning Predictions from Xparameters,” IEEE PA Symposium, San Diego, Sept. 2009
9. D. Gunyan , J. Horn, J. Xu, and D. E. Root, “Nonlinear Validation of Arbitrary Load X-parameter and Measurement-Based Device
Models,” IEEE MTT-S ARFTG Conference, Boston, MA, June 2009
10. G. Simpson, J. Horn, D. Gunyan, and D. E. Root, “Load-Pull + NVNA = Enhanced X-Parameters for PA Designs with High
Mismatch and Technology-Independent Large-Signal Device Models, ” IEEE ARFTG Conference, Portland, OR December 2008.
11. J. Horn, J. Verspecht, D. Gunyan, L. Betts, D. E. Root, and J. Eriksson, “X-Parameter Measurement and Simulation of a GSM
Handset Amplifier,” 2008 European Microwave Conference Digest Amsterdam, October, 2008
12. J. Verspecht, D. Gunyan, J. Horn, J. Xu, A. Cognata, and D.E. Root, “Multi-tone, Multi-Port, and Dynamic Memory Enhancements
to PHD Nonlinear Behavioral Models from Large-Signal Measurements and Simulations,” 2007 IEEE MTT-S Int. Microwave
Symposium Digest, Honolulu, HI, USA, June 2007.
13. D. E. Root, J. Xu, J. Horn, M. Iwamoto, and G. Simpson, “Device Modeling with NVNAs and X-parameters,” 2010 IEEE MTT-S
INMMiC Conference, Gοtenborg, Sweden, April 26, 2010
14. J. Horn, G. Simpson, D. E. Root, “GaN Device Modeling with X-parameters,” Accepted for publication 2010IEEE CSICS, Oct. 2010