R&S SGT100A User Manual page 155

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R&S SGT100A
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"Noise Only": a pure noise signal is generated and modulated to the carrier; the
connection to the baseband is interrupted.
Figure 7-2: Representation of an "AWGN > Mode > Noise Only" in the block diagram
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"CW Interferer mode": a sinusoidal signal with an adjustable frequency offset and
carrier-to-interferer (C/I) power ratio is added to the baseband signal by a counter
instead of a shift register.
Signal and noise parameters
The
Figure 7-3: Graphical representation of the relation between system bandwidth and noise bandwidth
System BW* = Occupied BW
The system bandwidth is a measure for the transmitted RF bandwidth. The selected
value is usually the occupied bandwidth and may therefore be a value greater than the
pure signal bandwidth.
In the most test cases, the signal and the noise power are not defined directly but by
the target's signal-to-noise ratio (SNR) or carrier/noise ratio.
The carrier power is a measure for the signal without the noise distribution.
To ensure flat noise within the selected system bandwidth, the noise bandwidth
should be larger than the system bandwidth. The minimum noise bandwidth is some-
times part of the specifications and is calculated as follows:
"Noise Bandwidth" = "System Bandwidth" x "Minimum Noise/System Bandwidth Ratio"
The calculated noise bandwidth may not exceed the total available bandwidth of the
instrument, as specified in the data sheet.
By default, the noise power within the system bandwidth is not defined directly but cal-
culated depending on the selected system bandwidth and the desired SNR. The noise
power over the noise bandwidth is calculated respectively.
User Manual 1176.8674.02 ─ 07
Figure 7-3 illustrates the relation between the signal and noise parameters.
(Minimum Noise/System BW = 2)
Additive White Gaussian Noise (AWGN) - Noise Generator
Signal Generator Settings
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