Adding noise and predistortions, and impairing the signal
R&S
®
SMM100A
268
User Manual 1179.1341.02 ─ 05
Mode
Activates/deactivates the generation of an AWGN signal. The interferer (AWGN or CW
interferer, depending on the selected mode) is generated after the generator is activa-
ted.
"Additive
Noise"
The AWGN noise signal with selectable system bandwidth is added
to the baseband signal.
"Noise Only"
The pure AWGN noise signal with selectable system bandwidth is
modulated to the carrier. The connection to the baseband is interrup-
ted.
"CW Interferer" A sine with a defined frequency offset is added to the baseband sig-
nal.
This mode is disabled in "System Configuration" with more than 4
input streams.
Remote command:
System Bandwidth
For "Additive Noise" and "Noise Only" modes, sets the RF bandwidth to which the set
carrier/noise ratio relates.
Within this frequency range, the signal is superimposed with a noise signal which level
corresponds exactly to the set C/N or S/N ratio.
For more information, refer to the description of
.
Remote command:
Minimum Noise/System Bandwidth Ratio
For "Additive Noise" and "Noise Only" modes, sets the ratio of minimum noise band-
width to system bandwidth, as required by some standards.
"Noise Bandwidth" = "System BW" x "Minimum Noise/System BW Ratio"
The parameter
displays the resulting noise bandwidth. Because the
noise power density is a constant value, increasing the noise/system bandwidth ratio
increases the noise bandwidth.
The calculation of level from the selected C/N or S/N ratio in relation to system band-
width is not influenced.
Remote command:
[:SOURce<hw>]:AWGN:BWIDth:RATio
Center Frequency Offset
Requires "Mode > Additive Noise/Noise Only".
Defines the frequency offset of the noise signal relative to the carrier center frequency.
Use the setting to shift noise signals relative to the output RF signal.
Remote command:
[:SOURce<hw>]:AWGN:FREQuency:CENTer:OFFSet
Target CW Frequency Offset
In "CW Interferer" mode, sets the desired frequency of the sine wave.
Adding noise to the signal