Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 287 / 813

R&S
®
ZVA/ZVB/ZVT Channel Menu
1145.1084.12 4.125 E-6
| DRECeiver, <attenuation>
Meas. Bandwidth
Sets the measurement bandwidth of the IF filter. Step Atten. b2 opens a submenu (and displays a range
of softkeys) to directly select bandwidths between 10 Hz and 1 MHz:
Fine Adjust... opens a dialog to modify the selected measurement bandwidth and the selectivity of the
IF filter.
•
Bandwidth shows the last IF filter bandwidth selected. The arrow buttons increment and
decrement the bandwidth in 1-2-5 steps for each decade. Entered values between the steps will
be rounded up, values exceeding the maximum bandwidth rounded down.
•
Selectivity selects between two types of IF filters: Filters with Normal selectivity and short
settling time, and filters with High selectivity but larger settling time.
The selected bandwidth and selectivity applies to all filters used in the current channel. This makes
sense because the measurement speed is limited by the slowest filter in the channel. In Segmented
Frequency sweeps, the bandwidth and selectivity can be set independently for each segment; see
Define Segments .
Optimizing the filter settings
A high selectivity and a small filter bandwidth both suppress the noise level around the measurement
frequency and thus increase the dynamic range. On the other hand the time needed to acquire a single
measurement point increases for small filter bandwidths and high selectivity. For small bandwidths, the
filter settling time, which is inversely proportional to the bandwidth, is responsible for the predominant
part of the measurement time.