Rohde & Schwarz R&S SMW200A - Page 427

Simulating Fading, Adding Noise and Predistortions, and Impairing the Signal
R&S
®
SMW200A
427User Manual 1175.6632.02 ─ 30
See also Chapter 6.2.2, "About the AWGN Generator", on page 416.
Remote command:
[:SOURce<hw>]:AWGN:POWer:MODE on page 1094
Reference Mode
Selects whether the carrier or the noise power is kept constant if the C/N or Eb/N0 ratio
is changed.
In the common case, the instrument keeps the carrier power and adjusts the noise
power accordingly. Some test cases however, for example the 3GPP base station tests
(TS 25.141), specify explicitly the noise power. These test cases require that the noise
power is permanently set as a function of the base station power class, whereas the
carrier power is variable.
Remote command:
[:SOURce<hw>]:AWGN:POWer:RMODe on page 1094
Bit Rate
In "Additive Noise" mode, indicates the bit rate used for converting C/N or S/N to E
b
/N
0
.
Tip: For digitally modulated signals, select the bit rate before or after channel coding,
as required.
See also Chapter 6.2.2, "About the AWGN Generator", on page 416.
Remote command:
[:SOURce<hw>]:AWGN:BRATe on page 1095
Carrier/Noise Ratio, Signal/Noise Ratio
In "Additive Noise" and "CW Interferer" mode, sets the carrier/noise, signal/noise or
signal/interferer ratio.
Whether a configuration of C/N or S/N is enabled, depend on the selected output Show
Powers For Output.
●
In "Reference Mode > Carrier": sets the noise power. It does not affect the power of
the useful signal, i.e. the carrier power remains constant.
Thus the power of the carrier + noise signal or the power of the output signal
changes.
●
In "Reference Mode > Noise", sets the power of the useful signal, i.e. the carrier
power.
The power of the output signal remains constant.
●
The power of the noise signal is derived from the entered C/N or S/N value and
displayed with the parameter "Noise Power" in the units of the useful signal.
●
The power of the useful signal is displayed with the parameter "Carrier Power" and
can also be changed there. This indication corresponds to the "Level" value in the
"Status bar".
●
The power of the output signal is displayed as "Carrier + Noise Power".
See also Figure 6-3.
Remote command:
[:SOURce<hw>]:AWGN:CNRatio on page 1095
E
b
/N
0
In "Additive Noise" mode, sets the ratio of bit energy to noise power density.
Adding Noise to the Signal