Common Measurement Settings
R&S
®
ESW
171
User Manual 1177.6298.02 ─ 08
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High attenuation helps you to avoid intermodulation
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High attenuation increases inherent noise (i.e. the noise floor) and thus decreases
measurement sensitivity: if you increase attenuation by 10
dB, the sensitivity is
reduced by 10
dB (in other words: the displayed noise increases by 10
dB)
Depending on the required test setup, a compromise must be found between a high
sensitivity, low intermodulation and input mixer protection. This is best done by letting
the R&S
ESW determine the ideal attenuation automatically.
You can determine the attenuation automatically with the auto ranging feature in the
receiver application and the auto attenuation feature in the other applications. Deter-
mining the attenuation automatically might not necessarily utilize the maximum
dynamic range, but still yields valid and reliable results.
When you select the attenuation manually and are measuring unknown signals, espe-
cially DUTs with a high RFI voltage, always select the highest possible attenuation
level before you apply the signal.
If you need a better sensitivity or signal-to-noise ratio, make sure that the applied sig-
nal does not exceed the specified limits, before you lower the attenuation.
For further protection of the input mixer, the R&S
ESW does not allow you to select
attenuation levels of less than 10 dB unless you explicitly turn on this feature ("
Risk of damage to the input mixer
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Do not apply a 0
dB attenuation when you measure unknown signals or RFI volt-
age in combination with an artificial network (LISN).
During phase switching, such test setups generate very strong pulses which can
damage the input mixer.
●
When you allow attenuation of less than 10
dB in combination with auto ranging,
make sure that the signal level at the RF input does not exceed the allowed limits.
Exceeding the limits can damage the input mixer.
10.7.1.2
Using the Preamplifier
The second tool that allows you to control measurement sensitivity is the preamplifier.
In addition to the standard preamplifier available in every R&S
ESW, an additional low
noise amplifier is available as an optional component (R&S
ESW-B24).
Signal gain has the following effects on the measurement:
●
The preamplifier allows you to detect even weak signals.
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The preamplifier reduces the noise figure of the R&S
ESW and thus increases its
sensitivity. Thus, it is recommended to use the preamplifier for measurements that
require maximum sensitivity.
●
The preamplifier reduces the dynamic range. If a measurement should be per-
formed at maximum dynamic range, you should turn off the preamplifier.
Amplitude and Vertical Axis Configuration
