Image Frequency Rejection - Rohde & Schwarz R&S FSW-K30 User Manual

®
R&S FSW-K30
Message
"Ext. Generator Command Error!"
"Ext. Generator Visa Error!!"
Risk of damage to the instrument
To allow for highest sensitivity during the measurement, the R&S FSW Noise measure-
ments application automatically sets the input attenuation to 0 dB.
Because this configuration minimizes the overrange reserve, make sure that the signal
you apply does not cause an overload condition. In particular, consider the LO feed-
through. An overload condition can damage or destroy the input mixer.
The FSW shows a corresponding message in the status line if an overload occurs ("RF
OVLD" or "IF OVLD").
To avoid an overload, do one of the following:
●
Reduce the LO feedthrough of the mixer device.
●
Increase the reference level.

4.5 Image frequency rejection

Frequency converting DUTs convert a radio frequency (RF) to an intermediate fre-
quency (IF). The IF is lower than the RF for down-converting DUTs, and higher than
the RF for up-converting DUTs.
In a basic test setup, the image frequency of the RF signal is also converted to the IF.
Depending on the DUT, this effect can be wanted or even necessary, or not. To avoid
measurement errors of the "noise figure" and "gain" of up to 3 dB, make sure to use
the appropriate measurement configuration.
Basically, you can distinguish between single sideband (SSB) mixers, double sideband
(DSB) mixers, and mixers that partly suppress a sideband. If a sideband is not needed
or only partly needed, you can reject the image frequency. If you do so, the application
activates a filter that suppresses the image frequency to a certain extent.
The following illustrations help you configure the measurement correctly.
For more information on how to configure image rejection, see
on page 54.
Double sideband measurements
Double sideband mixers use both sidebands to the same extent. Both RF and image
frequency are converted. In that case, turn off image rejection.
User Manual 1173.9270.02 ─ 31

Image frequency rejection

Description
Missing or wrong command in the generator setup file.
Error with Visa driver provided with installation (very
unlikely).
"Image Rejection"
Measurement basics
33