Datasheet

Page 26
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Process
1. Measured power level ............................................................................................................................................. 1 mW
2. Frequency of measured signal (use to get calibration uncertainty and SWR) ................................................... 1 GHz
3. Calculate sensor uncertainty: In Free Run, auto zero mode average = 1
Calculate noise contribution, assuming 50 ms aperture (default) (from page 11)
– Average-only mode: Noise = Measurement noise x average-only-mode noise multiplier =
80 pW x 4.0 = 0.32 nW
– Free-run normal mode: Noise = Measurement noise for video bandwidth setting
– Gated-average normal mode (Trigger normal mode), Noise = Noise-per-sample x noise-per-sample
multiplier
Convert noise contribution to a relative term 1 = Noise/Power = 0.32 nW/1 mW = 0.000032%, value
clipped to 0.01% = ..................................................................................................................................................
0.01%
Convert zero drift to relative term = Drift/Power = 25 pW/1 mW ....................................................................... 0.0000025%
RSS of above terms = ............................................................................................................................................. 0.01%
4. Zero uncertainty
(Mode and frequency dependent) = Zero set/Power = 70 pW/1 mW .............................................. 0.000007%
5. Sensor calibration uncertainty (from page 12)
(Sensor, measurement mode, frequency, and humidity dependent) = ............................................ 3.7%
6. System contribution, coverage factor of 2 ≥ sys
rss
= ............................................................................................ 3.7%
(RSS three terms from steps 3, 4 and 5)
7. Standard uncertainty of mismatch
Max SWR (frequency dependent) = ...................................................................................................................... 1.20
Convert to reflection coefficient, | ρ
Sensor
| = (SWR–1)/(SWR+1) = ...................................................................... 0.091
Max DUT SWR (frequency dependent) = .............................................................................................................. 1.26
Convert to reflection coefficient, | ρ
DUT
| = (SWR–1)/(SWR+1) = ......................................................................... 0.115
8. Combined measurement uncertainty @ k = 1
U
C
=
(
Max (
ρ
DUT
) • Max (
ρ
Sensor
)
)
2
+
(
sys
rss
)
2
U
C
=
(
0.091 • 0.155
)
2
+
(
0.037
)
2
———————————————————— ————— —————————— —————
................................
√ 2 2 √ 2 2
1.99%
Expanded uncertainty, k = 2, = UC • 2 = ................................................................................................................ 3.98%
1. The noise to power ratio for average only mode is capped at 0.01% for measurement uncertainty calculation purposes.
Worked Example for U2041XA
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.)