Operation
Model 8642A/B
RF Frequency Sweep (cont'd)
How to Set Sweep Time for Phase Continuous Frequency Sweep (Special Function 123)
(Understanding Limitations Between Sweep Spans and Sweep Times; Also, How to Set a Specific
Number of X-Axis Steps)
The operating characteristics for sweep time are as follows:
Minimum Sweep Time
Maximum Sweep Time
Sweep Time Resolution
Refer to calculation #3 on page 3-61
Refer to calculation #4 on page 3-6
1
1 ms
Since this type of frequency sweep sweeps in a phase continuous manner, no frequency
steps are used (although the X-axis output still uses steps). However, you might want to
choose frequency span and sweep time so each allows the other's settings (as described on
page 3-52). Also, you can calculate X-axis steps (available at the rear-panel output).
The information that follows will enable you to calculate:
1) the minimum sweep span for a desired sweep tune and frequency band (page 3-61),
2) the maximum sweep span for a desired sweep time and frequency band (page 3-61),
3) the minimum sweep time for a desired sweep span and frequency band (page 3-61),
4) the maximum sweep time for a desired sweep span and frequency band (page 3-61),
5) the number of automatically selected X-axis steps based on a sweep time setting
(page 3-62), and
6) the required sweep time to select a specific number of X-axis steps (page 3-62).
Since some of the calculations below use the frequency band divide number, the number
for each band is listed in the following table.
Band
10
9
8
7
6
5
4
3
2
1
Het
RF Frequency Range
1057.500001 to 2115.000000
(8642B only)
528.750001 to 1057.500000
264.375001 to 528.750000
132.187501 to 264.375000
66.093751 to 132.187500
33.046876 to 66.093750
16.523438 to 33.046875
8.261719 to 16.523437
4.130860 to 8.261718
0.100000 to 4.130859
0.100000 to 132.187500
Divide Number
0.5
1
2
4
8
16
32
64
128
16
1
If the frequency span is not possible from a divide band but would be possible if the Het
band was used, the Signal Generator will automatically select the Het band (if Special
Function 8, Prefer Heterodyne Band, is not selected). However, if the divide band or the
Het band could be used, the Signal Generator will select the divide band, i'or example, if
a sweep setting of 120.0 to 120.4 MI
r
z is selected, the Signal Generator will
automatically select the heterodyne band because a 400 kHz span is not possible in Band
6. But if a sweep setting of 120.00 to 120.03 MHz is selected, the Signal Generator will
automatically select band 6. (Refer to RF Frequency, page 3-39, for more information
about the divide bands and the heterodyne band.)
3-60
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