166Option EXM External MixingUsing Option EXM with the Keysight 11970 Series Mixers.Signal IDImage SuppressThe Image Suppress mode of Signal ID mathematically removes all image andmultiple responses of signals present at the mixer input. Two hidden sweeps aretaken in succession. The second sweep is offset in LO frequency by 2*IF/N. For eachpoint in each trace, the smaller amplitude from the two traces is taken and placed inthat point in Trace 1. Responses of each trace that lie on top of one another willremain 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 toactivating 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 shiftLike the Image Suppress mode, Image Shift is a two sweep sequence. The data fromthe first sweep is placed in Trace 1 and the data from the second (LO frequencyshifted by 2*IF/N) sweep is placed in Trace 2. Signal responses of Trace 1 and Trace2 that have the same horizontal position are considered to be in the current band andtherefore can be analyzed with the amplitude and frequency measurement systems ofthe 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 tracesprior to activating Image Shift will be lost.To synchronize in Image Shift Mode, turn off Signal ID and then initiate a singlesweep. Then turn on Signal ID and initiate two single sweeps. The results of the firstsweep after Signal ID is turned on are available in Trace 1. The next sweep is shiftedand the data from that sweep is available in Trace 2. The unshifted and shifted datacan then be compared.
