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28 Chapter 2
Operation
Using the Mixers with the E4440A, E4446A, or E4448A PSA Series Spectrum Analyzer (Option
AYZ)
Operation
Signal Identification
The IF output of a harmonic mixer will contain a signal at the intermediate frequency of the
analyzer whenever the harmonic frequency of the LO and the frequency of the RF differ by the
intermediate frequency.
As a result, within a single harmonic band, a single input signal can produce multiple responses on
the analyzer display, only one of which is valid (see Figure 2-6.). These responses come in pairs,
where members of the valid response pair are separated by 642.8 MHz and either the right-most
(for negative harmonics) or left-most (for positive harmonics) member of the pair is the correct
response.
Figure 2-6.
Identification of valid responses is achieved by simply turning on the signal-identification feature.
(instrument preset selects the Image Suppress signal identification mode.) Press
Input/Output, Input
Mixer
, Signal Ident (On) and note that now only the valid response (35 GHz) remains.
Press
Peak Search to place a marker on the remaining response. Refer to Figure 2-7.
After identifying a signal of interest, press
Signal Ident (Off) before making final amplitude
measurements. Note that Image Suppress should only be used to identify the fundamental signal
and not for accurate amplitude measurements.