Introduction to Noise Parameters
Transcript of Introduction to Noise Parameters
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1
Introduction to Noise Parameters
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2Noise Parameters
Noise Figure:
• Noise Performance at one Impedance
• Typical – 50Ω Noise Figure
Noise Parameters:
• Noise Performance at any Source Impedance
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3
( )
−+
−+=
22
2
min
114
sopt
opts
nrFF
n
optoptopt
r
F
→ |,|
min
Four Scalar Values:
nr
Noise Parameters
Imag s
Real s
opt
NF
minF
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4Noise & Gain Circles
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5Noise Parameters Measurement
• Set 4 Values of s
• For Each s, Measure F
• Solve 4 Simultaneous Equations for the 4 Values
𝐹 = 𝐹𝑚𝑖𝑛 + 4𝑟𝑛Γ𝑠 − Γ𝑜𝑝𝑡
2
1 + Γ𝑜𝑝𝑡21 − Γ𝑠
2
.
General Method
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6Noise Parameters Measurement
Practical Method
Use Over-Determined Data:
• Measurement is Sensitive to Small Errors
• Measure at more than 4 s Values
• Use Least-Mean-Squares to Reduce Data
Use Noise Power Equation:
• Rigorous Solution
• Account for hot and cold of Noise Source
• Allows Hot/Cold or Cold Only Approaches
𝑃 = 𝑘𝐵 𝑡𝑛𝑠 + 𝑡0(𝐹1 − 1) 𝐺𝐴1 + 𝑡0(𝐹2 − 1) 𝐺𝑇2
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Data Collection Methods 7
Traditional Method
Ultra Fast Method*
Very Time Consuming• Can Have Drift Issues • Data Scatter
• One Frequency at a Time• Allows Ideal Impedance Pattern• Based on 1969 Paper• Used by everyone for almost 40 years
• Characterize One Set Of Tuner States
• Sweep Frequency at Each State
• Take Advantage of Fast Sweep of Modern Instruments
*Invented by Maury Microwave
US Patent 8,892,380
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8Noise Parameters System Block Diagram
Typical Maury on-wafer noise parameters system
PNAX
NS
MT7553B03
DUT VNA
Bias
Power Supply
DUT
Switch Driver
GPIB
28V
NSMNoise
Source
VNA
Tuner
Bias
MT984AL01
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9Noise Parameters System Photo
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On-Wafer, 8-50 GHz, Fmin= 0.35 – 0.9 dB
Measured Data, No Smoothing Applied
Noise Parameters Measurement Results
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Data Outliers and Noise Data Processing 11
Outliers
• Transistor Data should be continuous• Noise Measurements are Over-Determined• Noise Data results should always come from one set of measured data.
Processing: • Data Outlier causes change from good data• Calculate Noise Parameters from Subsets to Remove Outliers• Errors add or cancel at different frequencies• Data Scatter vs Frequency is an Indicator of the measurement quality• Removing outliers tends to reduce scatter
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12
Noise Parameter Validation & Confidence in Measurements
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Measurement Confidence 13
System Accuracy is established using known devices:• Passive Verification Devices
• Active Device as Golden Standard
• Cascade Verification
System Repeatability must be a requirement• Measurement Repeatability
• Multiple calibrations
• Overlap bands with different tuners or receivers
• Comparison with other Labs
• Benchmark with legacy ATN systems
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Passive Device Measurement 14
A passive device tests accuracy of:• S-Parameter Measurements
• Noise Calibration
• Noise Measurement
Passive DUT
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Passive Device Measurement 15
Two Options:
• Matched Passive Device → Some Errors are Masked
• Mismatched Passive Device → Better Test
Known Limitation: System is tested at a different Gain Range than Active DUT
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Passive Device Measurement 16
0
1
2
3
4
5
6
7
8
9
10
7 12 17 22 27 32 37 42 47
Fmin
(d
B)
Freq (GHz)
6dB Mismatch comparison: NFmin
ATS_with NRM Passive verification
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Active Device as Golden Standard 17
• Challenges: • Selecting a stable bias condition for repeatable measurements
• Device wears out over multiple touch-downs
• Device performance can change over time
• Benefits:• System verification is established using similar DUT conditions
• Recommendations: • Multiple known devices based on reference measurements
• Limit the usage of these golden standards to system verification only
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18
DUT
1. Measure Noise
2. Measure S-Para
3. Measure Noise
4. Calculate Noise
DUT
Passive
Passive
DUTPassive +Compare
Cascade Verification
Advantage: System is tested at same Gain Range as Active DUT
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System Repeatability 19
• Measurement Repeatability
• S-parameters
• Multiple calibrations
• Overlapping bands with different tuners (same or different setups)
• Comparison between measurements at different sites
• Benchmark with legacy ATN system
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20Noise Measurement Repeatability
• On wafer Calibration measured over multiple days • Excellent repeatability
• Complete tear down and rebuilding setup• Multiple coaxial and on-wafer calibrations
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Nfm
in (
dB
)
Frequency (GHz)
6
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8
9
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12
13
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15
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Nfm
in (
dB
)
Freq (GHz)
Noise Calibration DUTRAW DATA
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Measurements at Different Sites 21
0
0.5
1
1.5
2
2.5
3
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
NFm
in (
dB
)
Freq (GHz)
Modelithics (FL)Maury (CA)
0
0.5
1
1.5
2
2.5
3
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
NFm
in (
dB
)
Freq (GHz)
Raw Data Processed Data
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Benchmark With Legacy ATN System 22
0.5
1
1.5
2
2.5
3
3.5
4
0 5 10 15 20 25
NFm
in(d
B)
Frequency (GHz)
ATS
ATN/NP5
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Critical Variables that Affect
Noise Parameters Measurements
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24With NRM
Without NRM
PNAX
NS
MT7553B03
DUT VNA
Bias
Power Supply
DUT
Switch Driver
GPIB
28V
NSMNoise
Source
VNA
Tuner
Bias
MT984AL01
Noise Receiver Module
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50N
fmin
(d
B)
Frequency (GHz)
Without NRM
With NRM
NRM To increase the sensitivity of DUT noise measurement a LNA stage is required.
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Maury Microwave Noise Receiver 25
Model Freq range Noise FigureMT7553B03 0.1-50GHz 10dB Typical
16dB Max
• Hold your solutions providers accountable!• Published vs actual data comparison
23456789
10111213141516
8 18 28 38 48
Nfm
in (
dB
)
Frequency (GHz)
On wafer calibration
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• Maury SW has the ability to calibrate at multiple attenuation levels • Dynamically chooses the right attenuation during DUT
measurements
Measurement Problems• Too much attenuation• Too low attenuation• Receiver overload
High Attenuation
Low Attenuation
Noise Receiver Attenuation
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3
2 4 6 8 10 12 14 16 18
Nfm
in (
dB
)Frequency (GHz)
High Attenuation
Low Attenuation
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27
Shields cell phone and wireless signals that can interfere with noise measurements.
0
1
2
3
4
5
6
7
8
0.8 3.2 5.6 8
NFm
in(d
B)
Freq (GHz)
Noise calibration (0.8 to 8 GHz)Screenroom No screenroom
interference point at 1.9 GHz
Screened Room (Faraday Cage)
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• Need a good Γ𝑆 spread at every frequency• Need to have the Γ𝑆 spread include high gamma values.
Bad Γ𝑆 spread Good Γ𝑆 spread
Typical Γ𝑂𝑃𝑇 DUT
Low Γ𝑆 spread
Gamma Source Selection
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Oscillation 29
DUT Γ𝑂𝑃𝑇
• At some high-gamma states, oscillation could occur
• MMC Software detects oscillation states and
removes them
• Points in the stability circle may not be unstable,
they are only Potential Unstable, stability also
depends on the output load
• But most high-gamma states are useful –
Γ𝑂𝑃𝑇 can be within stability circles