Graphical example, B. standard uncertainty of mismatch, C. combine a & b – Atec Agilent-N1921A User Manual
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Graphical Example
A. System contribution to measurement uncertainty versus power level (equates to step 6 result/2)
Standard uncertainty of mismatch - 1 sigma (%)
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0 0.1 0.2 0.3 0.4 0.5
ρ
Sensor
ρ
DUT
System uncertainty contribution - 1 sigma (%)
1.0%
10.0%
100.0%
-35 -30 -25 -20 -15 -10
-5
0
5
10
15
20
Power (dBm)
N1921A: 500 MHz to 10 GHz
N1922A:18 to 40 GHz
Other bands
Note: The above graph is valid for conditions of free-run operation, with a signal within the video bandwidth setting on the system.
Humidity < 70 %.
B. Standard uncertainty of mismatch
Note: The above graph shows the standard uncertainty of mismatch = ρDUT. ρSensor / ←2, rather than the mismatch uncertainty
limits. This term assumes that both the source and load have uniform magnitude and uniform phase probability distributions.
SWR
ρ
SWR
ρ
1.0
0.00
1.8
0.29
1.05
0.02
1.90
0.31
1.10
0.05
2.00
0.33
1.15
0.07
2.10
0.35
1.20
0.09
2.20
0.38
1.25
0.11
2.30
0.39
1.30
0.13
2.40
0.41
1.35
0.15
2.50
0.43
1.40
0.17
2.60
0.44
1.45
0.18
2.70
0.46
1.5
0.20
2.80
0.47
1.6
0.23
2.90
0.49
1.7
0.26
3.00
0.50
C. Combine A & B
U
C
= √ (Value from Graph A)
2
+ (Value from Graph B)
2
Expanded uncertainty, k = 2, = U
C
• 2 = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
± %