Measurement Accuracy - Keysight V3500A User Manual

Measurement accuracy

V3500A User's Guide
Since the power is constant over the interval T
the power is zero over the remainder of the interval T
average and peak power of pulse modulated signals are
related by the equation:
where
T is the pulse width of the signal.
1
T is the period of the waveform
2
In decibels, this would be expressed as:
P
,
peak dB
Mismatch error
Mismatch error is one of the primary factors affecting power
measurement accuracy. The goal is to measure the power
that a source will deliver into a load of impedance Z
power meter is designed to have an impedance as close as
possible to Z . Since its impedance is not exactly Z
0
power delivered to the meter is not exactly equal to the
power delivered to a perfect load.
Deriving the equations to calculate the mismatch error is
beyond the scope of this document, but the results can be
easily understood.
Consider the setup in
impedance Z is connected to a load of impedance Z
g
RF Measurement Basics
T
2
----- P
P =
peak avg
T
1
× ( ⁄ )
= 10 log T T
2 1
10
Figure 4- 4. A source of output
, and since
1
, the
1
+ P
,
avg dB
. The
0
, the
0
.
l
89
4