Measurements and Result Displays
R&S
®
ESW
103
User Manual 1177.6298.02 ─ 08
The resolution filters are implemented as digital Gaussian bandpass filters. Concerning
the attenuation characteristic, the filters behave like analog filters, but their measure-
ment speed is much higher than the measurement speed of comparable analog filters.
This is because the transient response can be compensated because the filters have
an accurately defined behavior.
The highest sensitivity is obtained at the smallest bandwidth. If the bandwidth is
increased, the reduction in sensitivity is proportional to the change in bandwidth.
Increasing the bandwidth by a factor of 3 increases the displayed noise by approx.
5
dB (4.77
dB precisely). If the bandwidth is increased by a factor of 10, the displayed
noise increases by a factor of 10 (= 10
dB).
The higher spectral resolution with smaller bandwidths leads to longer measurement
times at each frequency, because the measurement time has to allow the resolution fil-
ters to settle during a sweep at all signal levels and frequencies to be displayed.
For large measurement bandwidths, signal parts that are very far away (for example
from a different signal) are considered in the measurement and distort the results. The
displayed noise increases.
For small measurement bandwidths, the measurement time increases.
Bandwidths and detectors
If you use the Quasipeak, CISPR Average or RMS Average detector, the R&S
ESW by
default couples the resolution bandwidth to the receiver frequency.
If you need a different bandwidth, you can decouple the bandwidth from the frequency.
When decoupled, you can select any of the supported CISPR bandwidths.
9.3.1.2
Calculating the Number of Measurement Points
The number of measurement points (or sweep points in some applications) determines
the amount of data that is captured in one measurement. At each measurement point,
the R&S
ESW collects one set of data, which contains, for example, the signal level at
a given frequency.
The effect of the number of measurement points on the measurement is that its num-
ber defines how much of the entire span is covered by a single data point.
Example:
Consider the following settings:
●
Start frequency: 100 MHz
●
Stop frequency: 900 MHz
●
Number of measurement points: 1001
With said settings, each measurement point would cover a frequency range of about
800
kHz.
By increasing the number of measurement points, you can increase the reliability of the
individual data points and thus the accuracy of the analyzed results. All of these data
Test Automation
