Common Measurement Settings
R&S
®
FSW
418User Manual 1173.9411.02 ─ 43
Figure 8-18: Different mixer products displayed at the same frequency in the test sweep and refer-
ence sweep (large span)
Example:
The external mixer is set to use the 2nd order harmonic. The signal recorded in the test
sweep is displayed by trace 1. The IF filter of the R&S FSW is represented at a 3 dB
bandwidth of 20 kHz, the real IF bandwidth being 30 kHz. If, however, the 3 dB band-
width of the signal recorded in the reference sweep is examined (trace 2), it will be
found to be larger exactly by a factor of 2. This shows that the two products were gen-
erated by mixing with LO harmonics of different orders. The signal recorded in the test
sweep was generated by mixing with the 3rd order harmonic. Since the frequency axis
scaling is based on the 2nd order, the mixer product or the resulting diagram of the IF
filter is compressed by a factor of 2/3. The signal recorded in the reference sweep was
generated by mixing with the fundamental of the LO signal. Since the frequency axis
scaling is based on the 2nd order, the mixer product or the resulting diagram of the IF
filter is expanded by a factor of 2.
Automatic identification with a large span is not possible since the two mixer products
are displayed at the same frequency. The diagram shown in Figure 8-19 is obtained
when examining products with a narrow span using the Auto ID function. You can
easily recognize unwanted mixer products in the diagram obtained using one of the
automatic detection functions.
Data Input and Output
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