R&S ZNB Series User Manual page 227

®
R&S ZNB/ZNBT
Finding the appropriate algorithm
The three types of harmonic grids have different advantages and drawbacks. Note that
for a bandpass transformation the grid parameters have the following effect:
●
A wider sweep range (i.e. a larger bandwidth) increases the time domain resolu-
tion.
●
A smaller frequency gap extends the unambiguous range.
●
A larger number of points increases the sweep time.
With default analyzer settings, the differences between the grid types are small. The
following table helps you find the appropriate grid.
Table 4-21: Properties of grid types
Grid type: Keep
Stop freq. and no. of
points
Freq. gap and no. of
points
Stop freq. and approx.
freq. gap
4.7.2.5 Time gates
A time gate is used to eliminate unwanted responses that appear on the time domain
transform. An active time gate acts on the trace in time domain and in frequency
domain representation.
The properties of the time gates are analogous to the properties of the frequency
domain windows. The following table gives an overview:
Table 4-22: Properties of time gates
Window
Steepest Edges
(Rectangle)
Steep Edges
(Hamming)
Normal Gate
(Hann)
Maximum Flat-
ness (Bohman)
Arbitrary Gate
Shape (Dolph-
Chebychev)
User Manual 1173.9163.02 ─ 62
Sweep Time
time domain
resolution
Side lobe Passband
suppression ripple
13 dB 0.547 dB
43 dB 0.019 dB
32 dB 0.032 dB
46 dB 0 dB
User defined 0.071 dB
between 10 dB
and 120 dB
Concepts and features
Optional extensions and accessories
Unambig- Algorithm fails if...
uous
range
–
Stop frequency beyond upper fre-
quency limit
Number of sweep points beyond limit
Best for...
Eliminate small distortions in the vicinity of the
useful signal, if demands on amplitude accu-
racy are low
Good compromise between edge steepness
and side lobe suppression
Good compromise between edge steepness
and side lobe suppression
Maximum attenuation of responses outside the
gate span
Adjustment to individual needs; tradeoff
between side lobe suppression and edge
steepness
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