Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 222 / 813

Trace Menu R&S
®
ZVA/ZVB/ZVT
1145.1084.12 4.60 E-6
Gated and ungated state of the frequency domain representation
The trace in the frequency domain depends on the state of the Time Gate:
•
If the gate is disabled, the frequency domain trace corresponds to the sweep results prior to the
transformation.
•
If the gate is enabled, the frequency domain trace shown is calculated from the time domain
trace which is gated and transformed back into the frequency domain.
In time domain representation, you can use the Time Gate settings in order to eliminate
unwanted responses in your signal. After switching back to the frequency domain, you will receive the
frequency response of your DUT without the contribution of the unwanted responses.
Remote control: CALCulate<Ch/Tr>:TRANsform:TIME:STATe OFF
Time Domain
Selects the time domain representation for the active diagram area. The softkey is enabled if option
ZVAB-K2,
Time Domain, is available, and if a linear frequency sweep (Channel – Sweep – Sweep Type
– Lin. Frequency) is active. The analyzer automatically quits time domain representation as soon as a
different sweep type is selected.
In time domain representation the diagram shows the measurement results as a function of time. The
results are obtained by transforming the measured frequency sweep data into the time domain using an
appropriate mathematical transformation type and frequency window
(Define Transform...) . The sweep
range and the output power for the active channel is still displayed below the diagram; the displayed
time interval is shown in a second line:
Trace settings in time domain representation
While the time domain representation is active the trace settings behave as follows:
•
The settings in the Time Domain Stimulus Axis submenu configure the time axis.
•
All Trace Formats including the circular diagrams are available.
•
Limit lines can be defined like the limit lines for time sweeps.
•
The bandfilter search functions are available for the transformed trace.
•
If marker coupling is active, then the markers in the time domain and in the frequency domain
are coupled with each other.
The analyzer places no restriction on the measured quantities to be transformed into the time domain.
Impedances and admittances are first converted back into the equivalent S-parameter, transformed,
and restored after the transformation.
Properties of the Chirp z-transformation
The Chirp z-transformation that the analyzer uses to compute the time domain response is an extension
of the (inverse) Fast Fourier Transform (FFT). Compared to the FFT, the number of sweep points is
arbitrary (not necessarily an integer power of 2), but the computation time is increased by approx. a