62
Instrument Functions
Pushing the softkey TRACE MATH will open the menu of
the trace mathematics. After saving a trace in memory (via
the softkey TRACE
MEMORY) the difference between
the stored trace and the actual trace can be displayed
using the TRACE - MEM button. If there a trace is stored
the difference between the stored an the active trace will
be displayed by pushing the softkey MEM-TRACE. With
the softkey OFF the stored trace can be faded out. The
trace in the trace memory will be stored as bitmap file.
The R&S®HMS-X will not adapt the stored curve if the refe-
rence level or the displayed frequency range are changed.
6.7.4 Trace math functionality example with TG
Using the tracking generator (only available with
R&S®HMS-TG option resp. R&S®HV211 voucher) a spectral
analysis of hardware components should be done. For this
purpose, the DUT is looped into the signal path between
TG output and receiver input. Creating this loop requires
one or more RF cables.
The trace mathematics of the R&S®HMS-X spectrum
analyzer allows you to compensate the characteristics of
the RF cable(s) used. This is done by subtracting a stored
trace from an active trace and display the difference. To
measure the characteristics of the RF cable and to
compensate the connector the tracking generator output
will be connected to the input of the spectrum analyzer.
Now, the tracking generator function in the FREQ menu
will be activated. After activating the tracking generator
(softkey TRACKING GEN.) the red UNCAL message will
appear. This message indicates that the measurement with
the tracking generator is unaligned. The spectrum analyzer
shows the following trace:
Fig. 6.7 shows the transmission characteristics of the cable
and the connector. This curve will be stored with the soft-
key TRACE
MEMORY in the Memory menu (TRACE
button). The stored memory curve will be displayed by
pushing the SHOW MEMORY softkey. The spectrum ana-
lyzer shows the following trace:
Fig. 6.7: Tracking generator measurement unaligned
The following result will be displayed if you activate the
trace mathematics (TRACE MATH softkey) and choose the
softkey TRACE - MEM:
By calculating the difference between the recorded and
the stored curve, there is a differential curve of approxi-
mately zero, because the two curves are nearly identi-
cal (except the noise). The characteristics of the RF cable
are now compensated which will make UNCAL message
disappear.
Now that we have compensated the characteristics of the
RF cable we can make a little change in the measurement
setup by loosening the RF cable. By doing this we simulate
an antenna transmission which will result in the following
image:
Fig. 6.9: Aktivation of the trace math
Fig. 6.8: Display of the stored trace (Show Memory)
Summary of Contents for HMS-X
Page 82: ...82 Appendix ...
Page 83: ...83 Appendix ...
