Atec Agilent-N1921A - Manual (Page 8)

8
Characteristic Peak Flatness
The peak flatness is the flatness of a peak-to-average ratio measurement for various tone separations for an equal magni-
tude two-tone RF input. Figure 2 refers to the relative error in peak-to-average ratio measurements as the tone separation
is varied. The measurements were performed at –10 dBm with power sensors with 1.5 m cable lengths.
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
0 5 10 15 20 25 30
Input tone separation frequency (MHz)
Error (dB)
High
Medium
Low
(< 500 MHz)
Off
Off
(> 500 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 Zero drift 1
Noise per
sample Measurement noise
(Free run)
2
< 500 MHz > 500 MHz
N1921A /N1922A No RF on input 200 nW
100 nW 2 μW 50 nW
RF present 550 nW 200 nW
Measurement average setting 1 2 4 8 16 32 64 128 256 512 1024
Free run noise multiplier 1 0.9 0.8 0.7 0.6 0.5 0.45 0.4 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 hours 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 implemented, 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 car-
ried out every 1 μs 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.