Stanford Research Systems SR780, Operating Manual And Programming Reference

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Band Marker Menu 4-49
SR780 Network Signal Analyzer
ratio mode to measure THD+N (power with fundamental notched out/total power
including fundamental).
Command: BEXC (?) d {, i}
Band Ratio Mode
Select the Band Ratio Mode for the Band Marker in the active display [2/1, 2/(1+2)]. The
calculated ratio is displayed in the <Band Ratio> menu box.
2/1 specifies that the Band Ratio is computed from the ratio of the Upper (2) band power
to the Lower (1) band power.
2/(1+2) specifies that the Band Ratio is computed from the ratio of the Upper (2) band
power to the sum of the Lower (1) and Upper (2) band powers.
For example, to measure THD+N, use the Lower (1) band to define a small region around
the fundamental and the Upper (2) band to define the total bandwidth of interest. Exclude
‘1from2’ so the Upper (2) band does not measure the fundamental. Choose the 2/(1+2)
ratio mode to measure THD+N (power with fundamental notched out/total power
including fundamental).
Command: BRAM (?) d {, i}
Band Power
This menu box displays the Upper (top) and Lower (bottom) Band Powers of the active
display. The Band Power is the sum of the squared magnitudes of all bins within each
Band Marker. The result is shown in Vrms. (Square this result for power.)
Command: BPWR (?) d, i
Band Ratio
This menu box displays the band ratio, either 2/1 or 2/(1+2) as selected by the Band Ratio
Mode, for the active display. The result is shown in % and dB.
Command: BRAT (?) d, i