R&S FSQ Signal Analyzer - Rohde & Schwarz

R&S FSQ Instrument Functions
4.5.4.1 Filter Types
The R&S FSQ provides the following filter types.
Analyzer Mode
Normal (3 dB) Filter
The resolution bandwidths are implemented by Gaussian filters (analog 5-pole filter)
with the set 3 dB bandwidth. The resolution bandwidths correspond approximately
to the noise bandwidth. For bandwidths up to 100 kHz, digital bandpass filters with a
perfect Gaussian shape are used.
5-Pole Filter
The resolution bandwidths are implemented by 5-pole filters with the set 3 dB bandwidth.
The filters are approximations of a Gaussian filter.
For bandwidths up to 100 kHz, the digital bandpass filters operates with a near 5pole
shape. For bandwidths greater than 100 kHz it uses the same analog 5-pole filters
as the Normal 3 dB filter uses.
The 5-Pole filter is especially suited for measurements on signals with a steep
power ramp or for gated sweeps. This advantage results from the reduced group
delay time and the reduced settling time compared to a Gaussian filter.
However, with a shape factor from -60 dB to -3 dB, the filter’s shape factor is worse
compared to the perfect Gaussian shape of the Normal 3 dB filter.
5-Pole Digital Filter
The resolution bandwidths are implemented by 5-pole filters with the set 3 dB bandwidth.
The filters are approximations of a Gaussian filter.
For bandwidths up to 5 MHz, the digital bandpass filter operates with a near 5-pole
shape. For bandwidths greater than 5 MHz, the R&S FSQ uses the same analog 5pole
filters as the Normal 3 dB filter.
These digital filters are designed for minimized overshoot and it is a compromise
between 5-pole and gaussian shape.
The 5-Pole Digital filter is especially suited for measurements on signals with steep
power ramps. This results from the reduced power overshoot that the 5-Pole Digital
filter has.
Just like the 5-Pole filter, the 5-Pole Digital filter also has a faster settling time than a
Gaussian filter, but has an inferior shape compared to a Gaussian filter (-60 dB to -
3 dB bandwidth)
4.26 Operating Manual 1313.9681.12 - 01