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19-3
S-Parameter Commands
TDRSparam
If you move the reference plane to the second display division to the right of the display's left
edge, only data from eight display divisions is used. With the same 10 ns/div time scale and
1024 points-per-waveform setting, the maximum frequency will now be 6.4 GHz. As you can
see from the equation, as the time span decreases, the frequency span increases.
Frequency Span
Between Points
The number of points displayed on the screen is a result of the Fast Fourier Transform. If the
graph is drawn with too few points, you may want to increase the frequency resolution. Fre-
quency resolution is defined by the following equation:
Select a time span (acquisition interval) that is appropriate for your frequency data. Because
time and frequency are inversely related, decreased time spans result in increased frequency
resolution (fewer frequency data points). For example, with a 200 ps-per-division time-per-
division setting with data taken across the full 10 display divisions, the frequency resolution
equals 500 MHz. For the most information about your test device, place the reference plane
near the display's left edge and increase the time-per-division setting.
TDRSparam
Command :SPARameter:TDRSparam {ON | 1 | OFF | 0}
Turns on and off the S-parameter measurements, which also displays or hides the S-parame-
ter graph. Because the S-parameter calculations occure only when the graph shade is dis-
played, the graph must be displayed before S-parameter data can be saved to a file. Refer to
“SPARameter:SAVE” on page 10-8.
Example 10 OUTPUT 707;":SPAR:TDRS ON"
Query :SPARameter:TDRSparam?
Returned Format [:SPARameter:TDRSparam] {ON | 1 | OFF | 0}<NL>
MAGGraph:HORizontal:STARt
Command :SPARameter:MAGGraph:HORizontal:STARt <start_freq>
Sets the start frequency of the S-parameters graph. Depending on the span setting, the span
may need to be reduced before the start frequency can be changed.
Example 10 OUTPUT 707;":SPAR:MAGG:HOR:START 10E+6"
Query :SPARameter:MAGGraph:HORizontal:START?
Returned Format [:SPARameter:MAGGraph:HORizontal:STARt] <start_freq><NL>
MAGGraph:HORizontal:SPAN
Command :SPARameter:MAGGraph:SPAN <span_freq>
F
resolution
1
time/division()display divisions()
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