Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 236 / 813

Trace Menu R&S
®
ZVA/ZVB/ZVT
1145.1084.12 4.74 E-6
Compression point
The x-dB compression point of an S-parameter or ratio is the stimulus signal level where the magnitude
of the measured quantity has dropped by x dB compared to its value at small stimulus signal levels
(small-signal value). As an approximation for the small-signal value, the analyzer uses the value at the
start level of the evaluation range
(Eval Range...) .
The compression point is a measure for the upper edge of the linearity range of a DUT. It is close to the
highest input signal level for which the DUT shows a linear response (|a
n
| —> x*|a
n
| |b
n
| —>
x*|b
n
|, so that the magnitude of all S-parameters remains constant).
When Compression Point is activated, a marker labeled Cmp is placed to compression point with the
smallest stimulus level. Moreover the Trace Statistics info field shows the numerical results of the
compression point measurement:
•
Cmp In is the stimulus level at the compression point in units of dBm.
•
Cmp Out is the magnitude of the wave reflected or transmitted by the DUT. If an S-parameter
S
ij
is measured, then Cmp Out is the magnitude of the wave b
i
.
•
The ratio Cmp Out / Cmp In (in the example above: –14 dB) is equal to the magnitude of the
measured S-parameter or ratio at the compression point.
The info field shows invalid results ('---') if the wrong sweep type, trace format or measured quantity is
selected, or if the trace contains no x-dB compression points in the selected evaluation range.
Remote control: CALCulate:STATistics:NLINear:COMP:RESult?
Define Compression Value
Opens the numeric entry bar to define the compression value x (in dB) for the compression point
measurement.
Remote control: CALCulate:STATistics:NLINear:COMP:LEVel