5.2 Operating region curves for Agilent Acqiris digitizers
Several interrelated characteristics of both the Acqiris digitizers and the 89600 VSA software combine to form a region within which the VSA is constrained to operate. The 89600 VSA software characteristics that affect this operating region include maximum number of time points, the minimum number of time points (not user settable), a maximum acquisition record size (not user settable) and a maximum decimation factor (not user settable). The Digitizer characteristics that affect the operating region are sample rate and memory depth. This section describes the effects each of these parameters has on the VSA operating region.
The operating region is described in terms of span and time record length. For a given window type it could just as easily be described in terms of span and RBW. Figure 3 shows the effects of the number of time points the 89600 VSA software is allowed to collect. Because sample spacing is inversely proportional to span, the record length decreases as span increases. Although a family of lines is shown, only two define the operating region at any one time. The lowest line gives the smallest time record length allowed for any given span. The position of this line is determined by minimum number of time points (16) the VSA requires in a time record. The line that defines the upper time record length boundary is positioned by the maximum number of time points the VSA allows in a time record . The maxi- mum number of time points is determined by the Frequency Points setting (Meas- Setup/ResBWFrequency Points). The 89600 VSA is constrained to operate in the region between these two lines. Note that the operating lines of Figure 3 are the same for all digitizer models.
Operating region: number of frequency points limits
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Time record length |
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| 1.E+02 | 1.E+03 | 1.E+04 | 1.E+05 | 1.E+06 | 1.E+07 | 1.E+08 | 1.E+09 | 1.E+10 | 1.E+11 |
Span (Hz)
Figure 3. The user-settable parameter, frequency points, begins to determine the boundaries of the time record length and frequency span operating region
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