U2021XA Datasheet, PDF (17/20 Pages) Keysight Technologies – U2020 X-Series USB Peak and Average Power Sensors

17 | Keysight | U2020 X-Series USB Peak and Average Power Sensors – Data Sheet
Worked Example
Uncertainty calculations for a power measurement (settled, average power)
(Specification values from this document are in bold italic, values calculated on this page are underlined.)
Process
1. Power level:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Frequency: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3. Calculate sensor uncertainty:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
In Free Run, auto zero mode average = 16
Calculate noise contribution
– If in Free Run mode, Noise = Measurement noise x free run multiplier = 100 nW x 0.6 = 60 nW
– If in Trigger mode, Noise = Noise-per-sample x noise per sample multiplier
Convert noise contribution to a relative term¹ = Noise/Power = 60 nW/100 µW . . . . . . . .
Convert zero drift to relative term = Drift/Power = 100 nW/1 mW. . . . . . . . . . . . . . . . .
RSS of above terms =. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4. Zero uncertainty
(Mode and frequency dependent) = Zero set/Power = 200 nW/1 mW. . . . . . . . . . . . . .
5. Sensor calibration uncertainty
(Sensor, frequency, power and temperature dependent) =. . . . . . . . . . . . . . . . . . . . . . . .
6. System contribution, coverage factor of 2 ≥ sys_rss = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(RSS three terms from steps 3, 4 and 5)
7. Standard uncertainty of mismatch
Max SWR (frequency dependent) =. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
convert to reflection coefficient, | ρ_Sensor | = (SWR–1)/(SWR+1) =. . . . . . . . . . . . . . . . . . . .
Max DUT SWR (frequency dependent) = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
convert to reflection coefficient, | ρ_DUT | = (SWR–1)/(SWR+1) =. . . . . . . . . . . . . . . . . . . . . .
8. Combined measurement uncertainty @ k=1
( ) ( ) ^UC ⁼
Max(ρ_DUT ) • Max(ρ_Sensor )
2
+
sys_rss
2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
√2
2
Expanded uncertainty, k = 2, = U_C • 2 =. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 mW
1 GHz
0.06%
0.01%
0.061%
0.02%
4.0%
4.0%
1.20
0.091
1.26
0.115
2.13%
4.27%
1.  The noise to power ratio is capped for powers > 100 μW, in these cases use: Noise/100 μW.