User manual

44
Subject to change without notice
I n s t r u m e n t f u n c t i o n s
setting of the parameters is performed as described in chap-
ter 4. In order to assist the user when setting the sweep time,
an automatic selection of the sweep time with respect to the
RBW and the span settings may be chosen with the soft menu
key AUTO. The automatic mode will always set the sweep time
to the shortest possible value consistent with the correct
display of the spectrum content.
The HMS series will sweep the selected frequency range
continuously, i.e., after a sweep was completed, a new one will
be started and the display refreshed. If continuous sweeping
is not desired (e.g., if a single event shall be recorded upon
a trigger), there is also the possibility of selecting SINGLE
sweep. If single sweep is selected, the spectrum analyzer
will sweep the frequency range once or it displays the video
signal vs. time if the span is set to zero. The instrument will
only repeat the measurement after the soft key SINGLE was
pushed again.
Additionally the soft menu TRIGGER offers diverse trigger
functions in order to react to events.
– SOURCE: With the submenu SOURCE an internal or external
trigger source can be selected.
– SLOPE: With the softkey SLOPE the sweep of an external
trigger signal will be started by a positive or negative edge;
the external trigger signal is applied via the BNC connector
EXTERNAL TRIGGER (TTL logic levels).
Use the respective soft key for the selection of the desired
trigger mode.
5.7 Curve display settings (TRACE)
Pushing the key TRACE will call the settings menu. There are
several modes of curve display (TRACE MODE):
– CLEAR / WRITE (basic setting): The previous curve will be
erased during a new sweep.
– MAX HOLD: The maxima of the curve being measured and all
previous ones will be displayed. MAX HOLD allows to easily
ndintermittentsignalsinthespectrumorthemaximum
values of varying signals.
– MIN HOLD: The minima of the curve being measured and all
previous ones will be displayed. MIN HOLD allows to recover
periodic signals out of the noisefloorortosuppressinter-
mittent signals.
– AVERAGE: The average level of consecutive measurements
will be displayed. In the standard setting, averaging will be
performed pixel by pixel and over the last measured curves.
The average mode is hence suitable for an improved display
of periodic signals close to the noise level
– HOLD: Freezes the curve being displayed, the measurement
will be terminated, this allows to subsequently use the
markers for the measurement of spectra.
5.7.1 Trace Mathematics
The sub function TRACE a MEMORY allows to transfer a curve
to the background curve memory; by pushing the soft menu
key SHOW MEMORY it will be displayed and can be compared
to the presently displayed curve. The stored curve will always
be shown in white and thus can be easily differentiated from
the presently displayed curve. In order to let the stored curve
disappear, push the SHOW MEMORY key again.
Fig. 5.3: Display of a measured and a stored reference curve
The spectrum analyzer can subtract a stored curve from an
active curve and display the difference. If there is a curve
stored under TRACE a MEMORY the difference between the
stored an the active curves will be displayed by pushing the
soft menu key TRACE MATH. In order to let the stored curve
disappear push the key TRACE MATH and select OFF.
The TRACE MATH function can not be used in HOLD
mode.
Pushing the softkey TRACE MATH will call the menu of the
curve mathematics. After saving a trace in memory (via the
softkey TRACE a MEMORY) the difference between this
memory and the actual trace can be displayed using the
TRACE-MEM button. If there is a curve stored under TRACE
a MEMORY the difference between the stored an the active
curves will be displayed by pushing the softkey MEM-TRACE.
With the softkey OFF the saved waveform can be faded out.
The curve in the memory (Memory Trace) will be
stored in the video memory as a bitmap. The spec-
trum analyzer hence will not adapt the stored curve
if the reference level or the displayed frequency
range are changed.
5.7.2 Detector
A detector converts the video signal of a spectrum analyzer
before it will be displayed. It functions pixel by pixel, determining
how the value of a pixel will be measured. Pushing the soft menu
key DETECTOR will call the settings menu for the selection of
various types of detectors.
– AUTO PEAK: The spectrum analyzer will display the maxi-
mum and minimum value of each pixel from the frequency
range represented by that pixel, no signal will be lost; if the
signallevelfluctuates(noise), the width of the curve will
indicatethewidthofthesignalfluctuations(Basicsetting).
– SAMPLE: Only displays an arbitrary point within a display
pixel. The sample detector should be always used at span =
0 Hz, because this is the only method for a correct display of
the video signal vs. time. Can be used for the measurement
of noise power. For spans wider than than the resolution
bandwidth x 501, signals may be lost.