Instrument Function
R&S
®
SMBV100A
257Operating Manual 1407.6062.32 ─ 08
Internal Compensation
"Internal compensation" of signal distortions "of the RF output "can be activated / deac-
tivated.
Optimize internal IQ-Impairments for RF Output - Digital Impairments
Activates or deactivates internal compensation of signal distortions of the RF output.
Signal distortions can be either optimized for the RF output (active) or for the differential
I/Q output (not active).
SCPI command:
[:SOURce<hw>]:BB:IMPairment:OPTimization:STATe on page 588
Optimization Mode - Digital Impairments
Selects the optimization mode.
"Fast"
Optimization is reached by compensation for I/Q skew.
"High Quality"
Optimization is reached by compensation for I/Q skew and frequency
response correction.
SCPI command:
[:SOURce<hw>]:BB:IMPairment:OPTimization:MODE on page 588
5.6.2 AWGN - Noise Generator
The noise generator generates an AWGN signal (Additive White Gaussian Noise) in the
digital baseband, i.e. the noise power density has a Gaussian distribution and is distrib-
uted evenly across the frequency. This noise signal superimposes the (interference-free)
useful signal ("Additive Noise" mode). Typical applications for the noise generator are
bit-error or block-error measurements, depending on the set S/N or C/N ratio.
The Gaussian noise is generated by means of feedback shift registers with subsequent
probability transformation. The switching configuration is such that virtually ideal statis-
tical characteristics are achieved:
●
I and Q paths are decorrelated from each other.
●
The crest factor of 18 dB allows very small probabilities to be realized.
●
The period of the noise signal depends on the selected system bandwidth. The rela-
tionship of period P to system bandwidth B
sys
is approximated:
P ≈ 1*10
13
/ B
sys
This results in periods between 317 years with minimum bandwidth and approxi-
mately 2 days with maximum bandwidth.
This results in a period of approximately one month for 3GPP FDD with a bandwidth
of 3.84 Mcps, and a period of 427 days for GSM with 270.833 ksps.
Scalable low-pass filters are used to produce a noise level with both a broad dynamic
range and a broad bandwidth range (from 1 kHz to 60 MHz).
Apart from the "Additive Noise" mode, there are also the "Noise Only" and the "CW Inter-
ferer" mode. In the "Noise Only" mode a pure noise signal is generated and modulated
to the carrier. In the "CW Interferer mode", a sinusoidal signal with an adjustable fre-
Impairment of Digital I/Q Signal and Noise Generator - AWGN/IMP Block
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