08 | Keysight N1911A/N1912A P-Series Power Meters and N1921A/N1922A Wideband Power Sensors - Data Sheet
Characteristic Peak Flatness
The peak flatness is the flatness of a peak-to-average ratio measurement for various tone-separations for an equal magnitude two-
tone RF input. Figure 2 refers to the relative error in peak-to-average ratio measurements as the tone separation is varied. The mea-
surements were performed at –10 dBm with power sensors with 1.5 m cable lengths.
0.5
High
0.0
Off
-0.5
Medium
(> 500 MHz
Off
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
(< 500 MHz)
Low
0
5
10
15
20
25
30
Input tone separation frequency (MHz)
Figure 2. N192XA Error in peak-to-average measurements for a two-tone input (High, Medium, Low and Off filters)
Noise and drift
Sensor model
Zeroing
Zero set
< 500 MHz
200 nW
Zero drift1
Noise per sample
Measurement noise (Free run)2
> 500 MHz
200 nW
N1921A /N1922A
No RF on input
RF present
100 nW
2 μW
50 nW
550 nW
200 nW
Measurement average setting
1
2
4
8
16
32
64
128
0.4
256
512
1024
Free run noise multiplier
1
0.9
0.8
0.7
0.6
0.5
0.45
0.3
0.25
0.2
Video BW setting
Low 5 MHz
Medium 15 MHz
High 30 MHz
Off
Noise per sample multiplier
< 500 MHz
≥ 500 MHz
0.5
0.45
1
0.75
2
1.1
1
1
1. Within 1 hour after a zero, at a constant temperature, after 24 hour warm-up of the power meter. This component can be disregarded with Auto-zero mode
set to ON.
2. Measured over a one-minute interval, at a constant temperature, two standard deviations, with averaging set to 1.
Effect of video bandwidth setting
The noise per sample is reduced by applying the meter video bandwidth filter setting (High, Medium or Low). If averaging is implement-
ed, this will dominate any effect of changing the video bandwidth.
Effect of time-gating on measurement noise
The measurement noise on a time-gated measurement will depend on the time gate length. 100 averages are carried out every 1 us of
gate length. The Noise-per-Sample contribution in this mode can approximately be reduced by √(gate length/10 ns) to a limit of 50 nW.
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