Signal Id; Image Shift - Keysight X Series Measurement Manual

Option EXM External Mixing
Using Option EXM with the Keysight 11970 Series Mixers.

Signal ID

Image Suppress
The Image Suppress mode of Signal ID mathematically removes all image and
multiple responses of signals present at the mixer input. Two hidden sweeps are
taken in succession. The second sweep is offset in LO frequency by 2*IF/N. For each
point in each trace, the smaller amplitude from the two traces is taken and placed in
that point in Trace 1. Responses of each trace that lie on top of one another will
remain and are valid signals, others are images and are suppressed.
NOTE
This function takes control of and uses Trace 1. Any data in this trace prior to
activating Image Suppress will be lost.
In Image Suppress Mode, synchronization is ensured by first turning off Signal ID,
initiating a single sweep, then turning on Signal ID followed by two single sweeps.

Image shift

Like the Image Suppress mode, Image Shift is a two sweep sequence. The data from
the first sweep is placed in Trace 1 and the data from the second (LO frequency
shifted by 2*IF/N) sweep is placed in Trace 2. Signal responses of Trace 1 and Trace
2 that have the same horizontal position are considered to be in the current band and
therefore can be analyzed with the amplitude and frequency measurement systems of
the SA. All other responses are invalid and should be ignored.
NOTE
This function takes control of and uses Trace 1 and Trace 2. Any data in these traces
prior to activating Image Shift will be lost.
To synchronize in Image Shift Mode, turn off Signal ID and then initiate a single
sweep. Then turn on Signal ID and initiate two single sweeps. The results of the first
sweep after Signal ID is turned on are available in Trace 1. The next sweep is shifted
and the data from that sweep is available in Trace 2. The unshifted and shifted data
can then be compared.
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