19
Horizontal System
During peak detection, the oscilloscope distinguishes bet-
ween two types:
❙
Acquisition peak detection:
Each A/D converter converts at the full sampling rate (no
Interlace mode), even if results have not been written to
the acquisition memory at full sampling rate (for slow time
bases, for instance). If peak detection is activated, unused
converter values will be evaluated to detect minimum and
maximum amplitudes. During this process, the identified
minimum and maximum values including sampling
interval are written to the acquisition memory. As a result,
the acquisition memory stores data pairs representing the
signal sequence according to the sampling interval. The
smallest detectable pulse is the period of the maximum
sampling rate (no Interlace mode). This describes the
so-called acquisition peak detection.
❙
Memory peak detection:
A hardware peak detection is not available if data is
written to the acquisition memory at the ADC‘s maximum
sample rate. For slow time bases and the record mode is
set to AUTOMATIC or MA.WFM.RATE, not all data from
the acquisition memory will display on the screen. With
peak detection activated when reading out, skipped data
will be used to create a minimum and maximum value.
The smallest detectable pulse is the period of the sample
rate used to write to the acquisition memory. This
describes the so-called memory peak detection.
If one of the peak detection modes or a combination of
the two are used, the corresponding detection mode is
marked with „PD“ in the upper right of the display.
5 .3 .4 High Resolution
This mode uses Boxcar Averaging via adjacent detection
points (i.e. the converter runs at the maximum sampling
rate) to increase the vertical resolution to up to 16 bit. You
can deactivate this function within the menu (OFF) or you
can select the automatic switching mode (AUTO).
Averaging several adjacent sampling rates creates a value
with a higher degree of accuracy than the input data. The
resulting data is called high resolution data. The process
of merging multiple sampling rates to one new value only
allows a sampling rate that is smaller than the maximum
value. If the HIGH RESOLUTION mode is activated and
the current instrument setting allows the use of the HIGH
RESOLUTION mode, the detection mode is marked with
„HR“ in the upper right of the display.
The following requirements must be met to activate the
HIGH RESOLUTION mode:
❙
Sampling rate is smaller than the maximum sampling rate
(no Interlace mode)
❙
Peak detection is deactivated
❙
No active logic pod
❙
None of the serial or parallel buses are active
By default, all functions listed above are deactivated.
5 .3 .5 Interpolation
With the soft menu item INTERPOLATION users can se-
lect Sinx/x, Linear or Sample-Hold as interpolation type to
display acquired data points. The default setting is Sinx/x
interpolation which is the best option for displaying analog
signals. Linear interpolation (LINEAR) uses a line to con-
nect acquired data points. SAMPLE-HOLD allows a more
precise assessment of the position for the acquired data
points.
5 .3 .6 Record Mode
This soft menu item provides the following functions:
5 .3 .6 .1 MAX . WFM .-RATE
This mode allows you to select the memory depth and
sampling rate to obtain the maximum trigger repeat rate.
This mode allows you to select the memory depth and
sampling rate to obtain the maximum trigger repeat rate.
When using the MAX. WAVEFORM RATE mode, the oscil-
loscope is set to display the maximum amount of captures
per second in the signal window. Each column in the signal
window displays a captured date. When peak detection is
activated, each column displays a pair of min/max values.
The R&S®HMO1002 resp. R&S®HMO1202 series displays
a signal window of 600x400 pixels (Yt without zoom). This
translates into 600 data points per detection. When peak
detection is activated, 600 pairs of min/max values or 1,200
data values are displayed. The memory depth corresponds
to at least the displayed time window (time base x signal
window grid section in horizontal direction) multiplied by
the current sampling rate. The minimum value is deter-
mined by the maximum sampling rate and the maximum
signal repeat rate of the oscilloscope. The displayed samp-
ling rate corresponds to the current sampling rate divided
by the amount of data skipped while reading out from the
acquisition memory. If peak detection is activated, the dis-
played sampling rate corresponds to the current sampling
rate.
5 .3 .6 .2 MAX . SA . RATE
If this function is activated, the instrument always sets
the maximum sampling rate while using the maximum
memory available. The MAX. SAMPLE RATE function
always uses the maximum sampling rate and displays
Fig. 5.2: AM modulated signal with maximum repeat rate
