5-18
Optimizing Measurement Results
Reducing Receiver Crosstalk
Reducing Receiver Crosstalk
To reduce receiver crosstalk you can do the following:
• Perform a response and isolation measurement calibration.
• Set the sweep to the alternate mode.
Alternate sweep is intended for measuring wide dynamic range devices, such as high pass and bandpass
filters. This sweep mode removes a type of leakage term through the device under test, from one channel to
another.
To set the alternate sweep, press .
Refer to "Frequency Response and Isolation Error Corrections" on page 6-17.
Reducing Recall Time
To reduce time during recall and frequency changes, the raw offset function and the spur avoidance function
can be turned off. To turn these functions off, press
.
The raw offset function is normally on and controls the sampler and attenuator offsets. The spur avoidance
function is normally on and generates values as part of the sampler offset table. Depending on the state, the
creation of this table takes approximately 15
percent of the time during the recall of an instrument state.
To save time at recalls and during frequency changes, both functions should be turned off. This will avoid
generating the sampler offset table.
Raw offsets may be turned on or off individually for each channel. They follow the channel coupling. For dual
channel operation, raw offsets should be turned off for each channel if the channels are uncoupled. Spur
avoidance is always coupled between channels, therefore both channels are turned on or off at the same
time.
NOTE Both functions must be turned off to realize the recall time savings.
Refer to “Specifications and Characteristics” chapter in the reference guide for examples of recall state
times with the following functions on or off: raw offsets, spur avoidance, and blank display. Using blank
display may speed up recall times.
Understanding Spur Avoidance
In the 400 MHz to 3 GHz range, where the source signal is created by heterodyning two higher frequency
oscillators, unwanted spurious mixing products from the source may be present at the output. These spurs
can become apparent in filter measurements when filters have greater than 80 dB rejection.
Spur avoidance slightly moves the frequency of both oscillators such that the source frequency remains the
same but the spurious mixing products shift out of the measurement receiver range. The calculation of the
exact frequency points where the shifting must occur (stored in the sampler offset table) increases the time
needed to change or recall instrument states. Selecting
and
eliminates this calculation.
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