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4 Operation
4.1 Basic operation
Operation of the broadband VSA is substantially the same as that of the 89600
VSA. See the following sections for some differences or special confi gurations.
There is an online Tutorial and Getting Started Guide under the Help/Roadmap
toolbar in the 89600 software.
4.2 Sampling modes: full rate and user rate
Full rate mode
When the Sample Mode is set to full rate using the Utilities/Hardware/ADC1
/Agilent Acqiris One Channel Digitizer/Confi gure/Sample Mode/Edit menu
path for the U1065A-001 or Utilities/Hardware/ADC1 /Agilent Acqiris Two
Channel Digitizer/Confi gure/Sample Mode/Edit menu path for all the other
models, the digitizer sample rate is fi xed at the maximum for each digitizer
model according to Table 4.
With the addition of the anti-alias lowpass fi lter described above, this mode is
free of alias exposure zones. This means that no signal anywhere in the range
of the VSA’s center frequency will alias upon the desired signal and corrupt the
measurement.
There is a trade-off when using this mode. Although the digitizers have deep
memories allowing long record lengths, if a longer Main Time (or Result Length
for digital demodulation) is needed for more resolution in the frequency domain
a different sample mode may be required. Go to the Confi gure menu, click on
Sample Mode/Edit and select User Rate from the drop-down menu. The Main
Time limit for any sample rate is shown in the operating region curves that
appear in Appendix C.
NOTE: Any limitation to Main Time (or Result Length) will be indicated by the
inability of the software to increase the Main Time or decrease RBW when
Number of Frequency Points is increased.
Table 4. Sample rates of Acqiris digitizers in full rate mode
Digitizer model No. of channels Full sample rate
U1066A-001 (DC440) 1 400 M
U1066A-001 (DC440) 2 400 M
U1066A-002 (DC438) 1 200 M
U1066A-002 (DC438) 2 200 M
U1065A-001 (DC222) 1 8 G
U1065A-002 (DC252) 1 8 G
U1065A-002 (DC252) 2 4 G
U1065A-004 (DC282) 1 8 G
U1065A-004 (DC282) 2 4 G
8