Tektronix RSA6100A Series, Help Manual

Page: 324 / 415

Amplitude Corrections External Gain/Loss Correction Tab
External Gain Value
Use the External Gain Value setting to apply a fl at gain/loss correction to the signal. Positive values
represent a gain and negative values represent a loss. The range is –50 to +30 dB. Resolution is 0.1 dB.
NOTE.
Selecting Preset clears the check box, but it does not change the value.
Apply Table Corrections To
Use the two selections to specify whether the enabled external loss tables are applied to all acquired data
or only to traces in the Spectrum, Spectrogram, Spurious, and Amplitude vs Time displays.
When choosing whether to correct sample data or traces, keep the following in mind:
If sample data is acquired while data correction is enabled, that data record is permanently corrected.
If the acquisition is saved and recalled, the recalled acquisition includes corrections. Corrections
are not saved separately from the raw data; they are used during the acquisition process to adjust
the data values.
Trace corrections can be applied at any time, as they are part of the measurement’s computations.
Using Replay will apply trace corrections to a trace if this control is enabled (and an external loss
table is speci
fi ed and enabled).
Be aware that if you recall acquisition data that was saved with data corrections and you use Replay
with trace corrections selected and an external loss table enabled, the trace will be calculated using
corrected data and also corrected with trace corrections. This probably creates incorrect traces.
Trace Corrections Versus Data Corrections
Because of the real-time nature of the instrument and desire to frequently reanalyze stored acquisitions, it
is possible to apply amplitude corrections in real time. Applying real-time corrections to the incoming
data means that, the correction factors present during the acquisition are already part of the data when the
data is stored and then reanalyzed. This also allows the DPX Spectrum display to maintain its update rate
while presenting an amplitude-corrected display.
Real-time gain/loss factors are applied by creating a correction fi lter that is applied by the same digital
signal processing hardware used to correct for calibration and alignment factors in the instrument. This
process does have limitations. In creating a digital
fi lter to represent the gain/loss table, a limited number
of fi lter taps are be used in order for the fi lter to be practically realizable. If your amplitude corrections
contain discontinuities or extremely sharp transitions, the fi lter used will contains errors and ringing.
312
RSA6100A Series Real-Time Spectrum Analyzers Help