U2044XA Datasheet, PDF (10/25 Pages) Keysight Technologies – U2040 X-Series Wide Dynamic Range Power Sensors

10 | Keysight | U2040 X-Series Wide Dynamic Range Power Sensors – Data Sheet
Noise and drift
Mode
VBW setting
Zero set ¹
External zero
Normal ³
LOW/MED
HIGH/OFF
< 16 nW
< 50 nW
Average
100 pW for < 300 MHz
–
70 pW for ≥ 300 MHz

Average only mode noise multiplier
Internal zero
< 23 nW
< 60 nW
1 nW
Zero drift ²
< 10 nW
< 15 nW
< 25 pW
Measurement noise
< 10 nW ⁴
< 32 nW ⁴
< 80 pW ⁵
Noise per sample
< 0.15 µW
< 0.8 µW
-
The measurement noise due to the U2040 X-Series power sensor is dependent on the
measurement time. In general, the longer a measurement takes the lower the noise is.
The measurement noise specification is defined for 16 averages with an aperture of 50
ms, or a total time of 800 ms. Noise will reduce or increase with the square root ratio of
the measurement time to the specification measurement time. Thus a noise multiplier
√ factor can be derived for any combination of averaging and aperture:
N_mult =
————⁰——^.——⁸———— ^.
N_ave × t_a
Increasing measurement time will reduce noise at this rate until around 3 seconds. As the
measurement time increases beyond 3.2 seconds the noise reduction exponent changes
from 0.5 to 0.2.
( ) ^{Nmult = 0.89 ×}
1
N_ave× t_a
0.5
( ) ^{Nmult = 0.63 ×}
1
N_ave× t_a
0.2
, for N_ave × t_a ≤ 3.2
, for N_ave × t_a > 3.2
Noise_actual = N_mult × Noise_spec
Where N_ave ^def number of averages and t_a ^def aperture in seconds
1.  After 1 hour of warm up and at a constant temperature.
2.  After 1 hour of warm up and at a constant temperature, measurements taken over a period of 4 hours
after zeroing. Drift is calculated based on the average difference of any two measurements 1 hour apart.
3.  Only applicable to U2042XA/44XA.
4.  Noise defined for 1 average at free run mode.
5.  Noise defined for 16 averages at 50 ms aperture