Precision Power
Measurement Solutions
from Bird
Agenda
• National Standards Traceability- Challenges
& Bird’s Solution
• RF Metrology Paths at Bird Electronic
Corporation
–
–
–
–
–
High power RF Calorimetry
Low power microwave attenuation
Low power microwave power
MCS (master calibration system)
Test Setups & system considerations
• 4020 Series Power Sensors and the 4421
Power Meter
• Typical Field Power Measurement Systems
National Standards TraceabilityChallenges & Bird’s Solution
Generic Traceability Path
National Reference
Standard
Measurement
Reference Standard
Working Standard
Power Sensors
NIST
Bird Metrology
Bird Manufacturing
Facility
Power Measurement Requirements of the
Semiconductor Industry
Various
frequency &
power combos
40 kW
Power
13.56 Mhz
Frequency
Accuracy Capability of the
Scientific Community
Bird’s performance range
& capability
Power
NIST, NPL etc.
Frequency
Accuracy Capability of the
Scientific Community
Bird’s performance range
& capability
Calorimetry Path
Precision Attn & Power Path
Power
NIST, NPL etc.
Frequency
Bird’s Multi-Path Solution
High Power
RF Calorimetric Path
Low Power Precision
Attenuator
RF & Microwave Path
NIST AC & DC
Standard
NIST Attenation
Standard
Primary Lab
Low Power
RF & Microwave Power Path
< 10 mw
Primary
Standard
Thermistor
CN Mount
Working
Standard
Thermistor
Mount
Precision 60 Hz
Power Analyzer
Working
Standard
Measurement Ref.
Standard
MicroCalorimeter
< 10 mw
AC Voltage &
Current Stds.
NIST Fixed
Attenuator
Set
Working Standard
NIST
Standard
High Power
Calorimeter
VNA
Coupler Verification
Cal Factor
Verification
MCS Transfer
Standard
Couplers + Power Meter
Test Setups
4027, 4028
4024, 4025
Model 43
Calibration Subtleties of the Bird
System
•
•
•
•
•
+/- 1% calibration requirements dictate daily calibration
+/- 3% is calibrated every 6 months
+/- 5% is calibrated annually
Cross correlations are on-going and constant
Multiple paths are used to cross correlate high power &
high frequency standards
• It is capital intensive, time consuming, and demands
high skill levels, but worth every effort in order to
guarantee the high accuracy demands of the
semiconductor industry
RF Metrology Paths at Bird
Electronic Corporation
•
•
•
•
•
High power RF Calorimetry
Low power microwave attenuation
Low power microwave power
MCS (master calibration system)
Test Setups & system considerations
High Power RF Calorimetric Path
NIST AC & DC
Standard
Primary Lab
AC voltage &
Current Stds.
Working Standard
Precision 60 Hz
Power Analyzer
Measurement Ref.
Standard
High Power
Calorimeter
• Calorimetry is the critical link
between high power AC standards
& high power RF standards
Calorimetric Power Meters
6091
Power (kW) = .263 x flow rate (GPM) x T (0C)
8860
Calorimeter Block Diagram
Bird
Metrology
Manufacturing
Facility
Characteristics of Calorimetric
Power Meters
• Highly Accurate, Especially When Using
60Hz Substitution Technique
• Measures True Heating Power, Regardless of
Harmonic Content or Modulation
Characteristics of Signals
• Requires Careful Setup and Maintenance,
Due to Coolant Characteristics
• Long Settling Time
Specific Heat of Water
AC Substitution Method
60 Hz
AC Source
Precision
AC Power
Meter
RF
Calorimeter
RF
Source
• Measure 60 Hz power into calorimeter w/AC Power meter
• Adjust calorimeter display to match AC power meter
• Accuracy of AC standard has now been transferred to calorimeter
• When RF is supplied to load, read calibrated watts from calorimeter display
AC Substitution Technique
• Use Low Distortion 60Hz Source
• Calibrate Calorimeter Using Precision 60Hz Power
Meter (Accuracy = <0.1%)
• Apply Unknown RF Source to Calorimeter
• Adjust Coolant Flow Rate to Maintain ΔT Across
Load of > 2º C
• Allow 1 hour For Stabilization
Transfer of Accuracy from AC to RF
VSWR
AC (60 Hz)
RF
frequency
• Calorimetric load has virtually identical response at both AC & RF
-0.15
9/
11
9/
12
9/
13
9/
14
9/
15
9/
16
9/
17
9/
18
9/
19
9/
20
9/
21
9/
22
9/
23
9/
24
9/
25
9/
26
9/
27
9/
28
9/
29
9/
30
10
/1
10
/2
9/
10
Calorimetric Stability
% Error
0.2
0.15
0.1
Error
0.05
0
-0.05
-0.1
Days
Low Power Precision Attenuator
RF & Microwave Path
NIST Attenuation
Standard
< 10 mw
• Provides the important link
between low power, high frequency
attenuation values & high frequency
coupling values
NIST Fixed
Attenuator
Set
Working
Standard
VNA
Coupler verification
MCS Transfer
Standard
Working Standard
VNA
Precision
Coupler
• Transfers the accuracy of the
VNA to the precision coupler
when the coupling value is
determined
Attenuation Standards
• Attenuation kit traceable to NIST
VNA
Attenuation Kit
Low Power
RF & Microwave Power Path
NIST
Standard
MicroCalorimeter
< 10 mw
Primary
Standard
Thermistor
CN Mount
Working
Standard
Thermistor
Mount
MCS Transfer
Standard
Cal Factor
verification
Provides the link between high
frequency low power standards
and high frequency power meters
Working Standard
Thermal Power
Meter
CN Thermister
Mount
• Cal factor of power meter is verified
with reference to Thermister mount
MCS Transfer Standard
MCS Transfer
Standard
Provides the combinational accuracy
of calibrated high frequency power
& coupling standards into a single calibrated
device that can be used as a measurement
standard in a high frequency, high power test
setup
Directional Coupler - Thermal
Power Meter MCS Standard
Characteristics of Directional CouplerThermal Power Meter Standards
• Wide Dynamic Range
• Useful Frequency Range Determined by Directional Coupler
• Complicated Error Budget
– Internal Reference Uncertainty
– Mismatch Uncertainty
– Calibration Factor Uncertainty
• Fundamental Accuracy Limited by Knowledge of Directional
Coupler Attenuation, as well as Power Meter Error Sources.
• Mismatch Uncertainty is a Major Contributor to Total
Uncertainty
Precision Power Measurement
Test Setups
Test Setups
4027, 4028
4024, 4025
Model 43
4027A +/-1% Calibration System
These two measurements must
agree within +/- .2%
Test Results 4027A
Test Results
1.00
Difference from Calorimeter (%)
0.80
0.60
0.40
SN 11569
MCS-59 w ith 11569
0.20
SN 11596
MCS-59 w ith 11596
0.00
-0.20
SN 11597
5
10
15
20
25
30
35
40
45
50
55
60
MCS-59 w ith 11597
SN 11598
MCS-59 w ith 11598
-0.40
-0.60
-0.80
-1.00
Elapsed Time (minutes)
A Typical Field Calibration Setup
Bird 4020AM
Power Sensor
p2
p1
p2
RF Matching
Network
p1
p2
p1
Bird Oil load
5 kW RF Generator at
13.56 MHz
p2
Plasma
Etching
Chamber
Bird 4421
Power Meter
Mismatches are present at each interconnection
of system components
Mismatch Uncertainty
p 2p 1p 2 S
p 1p 2 S
p1
p2
S
p 2S
Total reflected signal
p2 +/- p1p2p2 = p2’
Mismatch Uncertainty
VSWR (apparent) =
1 + p2’
p2 +/- p1p2p2 = p2’
1–
p2’
VSWR (apparent) = 1 + ( p2 +/- p1p2p2 ) =
1 - ( p2 +/- p1p2p2 )
1 + p2 +/- p1p2p2
1 - p2 -/+ p1p2p2
Recognize that this expression can be
approximated as the product of
Very small contribution
1 + p2
1 – p2
x
1 +/- p1p2p2
1 -/+ p1p2p2
=
1 +/- p1p2p2 + p2 +/- p1 p32
1 -/+ p1p2p2 + p2 +/- p1 p32
Then:
VSWR (true) x
1 +/- p1p2p2
1 -/+ p1p2p2
~
VSWR (apparent)
Mismatch Uncertainty
VSWR (true) x
1 +/- p1p2p2
1 -/+ p1p2p2
~
VSWR (apparent)
• The true VSWR is multiplied by an uncertainty factor which can only be controlled
by carefully choosing the reflection coefficients (p1 and p2) at the source and test points
Lower limit of multiplier factor =
1 - p1p2p2
1 + p1p2p2
Lower uncertainty limit of measured VSWR = F-
Upper limit of multiplier factor =
1 + p1p2p2
1 - p1p2p2
Upper uncertainty limit of measured VSWR = F+
= F-
1 + p2
1 – p2
= F+
1 + p2
1 – p2
Mismatch Uncertainty
Mu (%) = 100 [(1 ± Pg Pl)2 – 1]
Where:
Pg = Reflection Coefficient of Source
Pl = Reflection Coefficient of Load
Pg and Pl are FREQUENCY DEPENDENT QUANTITIES!
VSWR Mismatch Uncertainty
3
1.1 source VSWR
VSWR Uncertainty
2
1.1 source VSWR
1.5 source VSWR
1
1.5 source VSWR
2.0 Source VSWR
0
1
2
3
-1
4
5
2.0 Source VSWR
2.5 Source VSWR
2.5 Source VSWR
3.0 Source VSWR
3.0 Source VSWR
3.5 Source VSWR
3.5 Source VSWR
-2
-3
Load VSWR
Transmission Uncertainty
p 2p 1p 2 S
p 1p 2 S
p1
p2
S
p 2S
Total transmitted signal
S(1 +/- p1p2)
+/- dB (ripple) = 20 log | 1- p1p2 |
Transmission Uncertainty
High point
flatness
Ripple averaged
out
Low point
• If data is taken at discrete points, then each individual
reading carries an uncertainty of +/- x dB
Measurement
uncertainty
Transmission Uncertainty
4.5
4
Uncertainty +/- dB
3.5
3.5 Source VSWR
1.1 Source VSWR
3
1.5 Source VSWR
2.5
2.0 Source VSWR
2
2.5 Source VSWR
3.0 Source VSWR
1.5
3.5 Source VSWR
1
1.1 Source VSWR
0.5
0
1
2
3
Load VSWR
4
5
Transmission Uncertainty
0.25
Uncertainty +/- dB
0.2
1.1 Source VSWR
1.15 Source VSWR
0.15
1.2 Source VSWR
1.25 Source VSWR
0.1
1.3 Source VSWR
1.35 Source VSWR
0.05
0
15
20
25
30
Load Return Loss (dB)
35
40
Example of Typical RF System Error Budget
Prototype RF Delivery System Gain/Mismatch Analysis
Power
Sensor
Matching
Network
Cable
Cable
Cable
RF
Generator
No.
Termination
Device
Return Loss
(dB)
Input
1
2
3
4
5
6
7
8
9
10
Generator
cable
Power Sensor
cable
Matching Network
cable
termination
Total
25.00
30.00
30.00
30.00
30.00
37.00
Output
25.00
30.00
30.00
30.00
30.00
37.00
Gain/Loss
(dB)
Mag.
-0.010
-0.025
-0.010
-0.050
-0.010
-0.11
(db)
Ripple
0.03
0.02
0.02
0.02
0.01
+/- 0.05
Watt Budget
Watts In
Watts out
dbm out
1700.0
1696.1
1686.4
1682.5
1663.2
1,700.0
1,696.1
1,686.4
1,682.5
1,663.2
1,659.4
62.30
62.29
62.27
62.26
62.21
62.20
Low Uncertainty
1,642.1
62.15
62.24
Hi Uncertainty
1,676.8
1659.4
stage loss
Cumulative loss
3.9
9.7
3.9
19.3
3.8
0.0
3.9
13.6
17.5
36.8
40.6
40.6
Delta Watts
34.7
Prototype RF Delivery System Gain/Mismatch Analysis
Powe r
Se nsor
Ma tching
N e twork
Ca ble
Ca ble
Ca ble
RF
Ge ne ra tor
No.
T e rmina tion
Device
Return Loss
Input
1
2
3
4
5
6
7
Generator
cable
adapter
adapter
Power Sensor
adapter
adapter
cable
adapter
Matching Network
adapter
adapter
cable
adapter
adapter
termination
Total
25.00
26.44
26.44
30.00
26.44
26.44
26.44
26.44
30.00
26.44
26.44
26.44
26.44
26.44
37.00
(dB)
Output
25.00
26.44
26.44
26.44
30.00
26.44
26.44
26.44
26.44
30.00
26.44
26.44
26.44
26.44
26.44
Gain/Loss
Watt Budget
(dB)
Mag.
(db)
Ripple
Watts In
Watts out
dbm out
stage loss
Cumulative loss
-0.010
-0.005
-0.005
-0.025
-0.005
-0.005
-0.010
-0.005
-0.050
-0.005
-0.005
-0.010
-0.005
-0.005
0.05
0.04
0.04
0.02
0.04
0.04
0.04
0.04
0.02
0.04
0.04
0.04
0.04
0.04
1700.0
1696.1
1694.1
1692.2
1682.5
1680.5
1678.6
1674.7
1672.8
1653.7
1651.8
1649.9
1646.1
1644.2
1,700.0
1,696.1
1,694.1
1,692.2
1,682.5
1,680.5
1,678.6
1,674.7
1,672.8
1,653.7
1,651.8
1,649.9
1,646.1
1,644.2
1,642.3
62.30
62.29
62.29
62.28
62.26
62.25
62.25
62.24
62.23
62.18
62.18
62.17
62.16
62.16
62.15
3.9
2.0
1.9
9.7
1.9
1.9
3.9
1.9
19.1
1.9
1.9
3.8
1.9
1.9
0.0
3.9
5.9
7.8
17.5
19.5
21.4
25.3
27.2
46.3
48.2
50.1
53.9
55.8
57.7
Low Uncertainty
1,547.7
61.90
62.41
Hi Uncertainty
1,742.6
57.7
Delta watts
194.9
-0.15
+/- 0.26
1646.1
4027A +/-1% Calibration System
These two measurements must
agree within +/- .2%
Effects of Harmonics on Power
Measurement
• 4027 Power Sensor Detector Scheme is Very
Sensitive to Harmonics in the Signal.
• 4027 is Calibrated with Signals Having
Harmonics of Less than –60dBc.
• Signals with Harmonic Content Greater Than
–60dBc will Cause Offsets in Power Readings
• Effects of Harmonics are Determined not
Only by Diode Response, but Also by
Directional Coupler Response
Characteristics, as well as Phase
Relationships of Harmonic.
Effects of Harmonics on Power
Measurement
Worst Case Errors
% Error
% Error
% Error
Harmonic with One with Two with Three
Level
Harmonic Harmonics Harmonics
-55
0.36%
0.70%
1.00%
-50
0.63%
1.10%
1.80%
-45
1.10%
2.10%
2.90%
-40
1.90%
3.90%
5.80%
Effects of Modulation on Power
Measurement
• Detector Scheme Used in 4027 is Sensitive to
Amplitude Modulation of the Signal.
• Magnitude of Change in Power reading is
Related to Power Level and Instrument
Range.
• Approximate Error:
– At 10% of Full Scale: 5% AM Results in 2% Error
– At 90% of Full Scale: 5% AM Results in 8% Error
Additional Tips for Making
Accurate Power Measurements
• Know the effects of the mismatches present in the system architecture on
the power measurement uncertainty
• Avoid the use of multiple adapters or non-compensated (high VSWR)
adapters between cables and components
• Perform a system error budget to quantify the effects of mismatches and
component tolerances in the system
• Avoid the use of long interconnecting cables, as the ripple period will be
more frequent as the length is increased for a given frequency
• Use coupler based measurement techniques when the load is unstable or
poor in performance compared to the system line impedance
• Averaging techniques over wider frequency bands can be effective in
minimizing the effect of mismatch uncertainties
4020 Series Power Sensors and
the 4421 Power Meter
4421/4020 Series Power Meters
• Highly Accurate, Highly Repeatable Power Meter
System
• Long Product History, Introduced in 1988
• Has Become the Power Meter of Choice in
Semiconductor Processing Applications
• Extremely Wide Dynamic Range
4027A Precision
Power Sensor
Model
Power Range
Frequency
VSWR Range
Directivity
Insertion Loss
4027A12M
300 mW to 1 kW
10-15 MHz
1.0 to 2.0
28 dB
<0.05 dB
4027A250K
3 W to 10 kW
250-400 kHz
1.0 to 2.0
28 dB
<0.05 dB
4027A400K
3 W to 10 kW
400-550 kHz
1.0 to 2.0
28 dB
<0.05 dB
4027A800K
3 W to 10 kW
800-950 kHz
1.0 to 2.0
28 dB
<0.05 dB
4027A2M
3 W to 10 kW
1.5-2.5 MHz
1.0 to 2.0
28 dB
<0.05 dB
4027A4M
3 W to 10 kW
3-5 MHz
1.0 to 2.0
28 dB
<0.05 dB
4027A10M
3 W to 10 kW
10-15 MHz
1.0 to 2.0
28 dB
<0.05 dB
4027A25M
3 W to 10 kW
25-30 MHz
1.0 to 2.0
28 dB
<0.05 dB
4027A35M
3W to 10 kW
35-45 MHz
1.0 to 2.0
28 dB
<0.05 dB
4027A60M
3W to 6kW
45-65 MHz
1.0 to 2.0
28dB
<0.05 dB
• Designed for Service in Semiconductor Processing Applications
• ± 1% Accuracy at Calibration Points
• Several Models to Address Specific Semiconductor Power Levels
and Frequencies
4027 true average responding detector scheme
VOUT
=
VIN
2
5.77
• First generation diode detectors
operate over transition region of diode
response curve limiting use in
modulated communications systems.
• The entire dynamic range of the 4027
series sensor is contained within the
square law operating range of the
detector
• Sensor will behave similar to a thermal
device, responding to the heating
power of the signal being measured
4027A Power Sensor
4027F Power Sensor
LP Filter
LP Filter
4027A Power Sensor
1
2
3
4
5
Error Budget
Error Source
4027A Limit
R2
Calibration Standards Uncertainty
± 0.4%
0.16
Frequency Response Error
0.0%
0
Dynamic Linearity
± 0.5%
0.25
Temperature Effects
± 0.5%
0.25
Noise
± 0.5%
0.25
Worst Case Error
± 1.9%
RSS (Probable) Error
± 0.91%
Notes:
Based upon a temperature range of +35 degrees celcius.
4027A Typical Linearity, 13.56 MHz
0.30
0.20
4027A10M
Serial #
0.10
S/N#11758
S/N#11759
0.00
0.50
1.00
1.50
2.00
2.50
3.00
S/N#11822
S/N#11823
S/N#11817
% Error
-0.10
Power Levels (kW)
S/N#11818
S/N#11820
S/N#11821
-0.20
S/N#11824
S/N#11825
S/N#11826
-0.30
-0.40
-0.50
4027A Typical Linearity, 12 MHz
4027A10M Serial #
Power Levels in
(kW)
.5kw
1kw
1.5kw
2.0kw
2.5kw
3.0kw
11596 11597 11598
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.60
0.20
0.10
-0.07
-0.50
0.00
Short Term Drift at Elevated Power Level
4027A10M S/N#11820
100w
1000w
3000w
Time (Min) 15
4027A10M
4027A10M
4027A10M
Min Warmup MCS-59 (w)
(w)
MCS-59 (w)
(w)
MCS-59 (w)
(w)
0
99.8
99.8
1009
1009
3.01
3.01
5
99.6
99.6
1008
1008
3.01
3.01
10
99.5
99.5
1009
1009
3.00
3.00
15
99.6
99.6
1010
1010
2.99
2.99
20
99.7
99.7
1012
1012
2.98
2.98
25
100
100
1013
1013
2.98
2.98
30
100
100
1011
1011
2.99
2.99
35
100
100
1009
1009
2.99
2.99
40
99.6
99.6
1011
1011
2.98
2.98
45
99.3
99.3
1013
1013
2.99
2.99
50
99.6
99.6
1015
1015
2.99
2.99
55
99.4
99.4
1013
1013
2.97
2.97
60
99.3
99.3
1009
1009
2.97
2.97
Higher Power 4028 Capability
4028A
1-5/8” or 3-1/8”
Transmission
Line
• Similar Accuracy To Other 4027 Models
• Uses Larger Transmission Line (1-5/8”
or 3-1/8”) Flanged or Unflanged
• Power Measurement Capability Up To
40Kw
Typical Field Power Measurement
Systems
A Typical Power Measurement Setup
Utilizing a Directional Coupler
Wattmeter
Forward
watts
Reverse
watts
Amplifier
Source
p2
p1
p1
p1
p2
Directional
Coupler
p2
High Power
Termination
Coupler Based Measurements
Advantages:
• Typically not limited by power- very little power dissipated
• Typically have good thru line reflection coefficients
• Forward Power readings are basically isolated from load
stability issues
• Allows in-line monitoring of signal with actual system load
Disadvantages:
• Must know the coupling value very accurately
• Directivity limits reflected power reading
• Frequency bandwidth limited
A Typical Power Measurement Setup utilizing an
Attenuator and Thermal Power Meter
Wattmeter
Thermal
Sensor
Amplifier
Forward
watts
Source
Attenuator
• Knowledge of the attenuation factor and stability is crucial
to making a precise power measurement
Attenuators and Their Effect
On Accuracy
Forward
Power
attenuation
+/- attn.
tolerance
Output
power
Low
reading
High
reading
+/- % fwd
power change
1000
30
0.01
1
0.998
1.002
0.23
1000
30
0.1
1
0.977
1.023
2.28
1000
30
0.25
1
0.944
1.059
5.59
1000
30
0.5
1
0.891
1.122
10.87
• Assuming nominal attenuation value can lead to significant errors
• Errors can be minimized by calibrating the attenuator at the specific
frequency or band of frequencies
Attenuator Based Measurements
Advantages:
• Wideband frequency response, DC coupled
• Convenient to use, eliminates a termination
Disadvantages:
• Limited in power dissipation
• Attenuation accuracy is often not precise, not
as stable
• Reflection coefficients are generally higher
Attenuator Based Measurements
• Uncertainties Associated With This System
– Input Mismatch Uncertainty (Typically Small Due to Low
Input VSWR)
– Output Mismatch Uncertainty
– Uncertainties Associated With Thermal Power Meter
– Attenuation Factor Uncertainty
– Stability of Attenuation Factor Over Temperature
– Additional Thermal Errors Due To Excessive Load
Temperatures Affecting Thermal Power Sensor
When an attenuator is used, obtain the calibrated attenuation factor from the
manufacturer (or make the measurement yourself) for best possible
precision measurements.
Summary
• National Standards Traceability- Challenges & Bird’s Solution
– Bird’s multi-path solution and test capabilities make it
unique in the industry
• RF Metrology Paths at Bird Electronic Corporation
– High accuracy transfer of standards at every step of the
way
– Know the concepts behind the error sources in a test setup
• 4020 Series Power Sensors and the 4421 Power Meter
– +/- 1% power sensor ideal for semiconductor industry
• Typical Field Power Measurement Systems
– Know your system and the errors associated with it