Rohde & Schwarz SMW200A - Bit Rate; Carrier;Noise Ratio, Signal;Noise Ratio; E B;N

Simulating Fading, Adding Noise and Predistortions, and Impairing the Signal
R&S
®
SMW200A
400User Manual 1175.6632.02 ─ 16
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 1007
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 5.2.2, "About the AWGN Generator", on page 390.
Remote command:
[:SOURce<hw>]:AWGN:BRATe on page 1008
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 power of the output signal, i.e. the carrier +
noise signal.
It does not affect the power of the useful signal, i.e. the carrier power remains con-
stant.
●
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 5-3.
Remote command:
[:SOURce<hw>]:AWGN:CNRatio on page 1008
E
b
/N
0
In "Additive Noise" mode, sets the ratio of bit energy to noise power density.
●
In "Reference Mode > Carrier": sets the noise power and hence the power of the
output signal, i.e. the carrier + noise signal.
It does not affect the power of the useful signal, i.e. the carrier power is kept con-
stant.
●
In "Reference Mode > Noise": sets the power of the useful signal, i.e. the carrier
power.
The noise power is kept constant.
Adding Noise to the Signal