HP 8510, Руководство пользователя

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Pulse Repetition P eriod and Duty Cycle Considerations
F rom this information it can b e seen that the pulse rep etition p erio d and th us the dut y cycle
of the pulsed-RF signal applied to the DUT can v ary dep ending up on the instrumen t state.
F or measuremen ts in whic h the PRP or dut y cycle is not imp ortant, simply set the pulse
width and the dut y cycle con trols to an appropriate v alue and make the measuremen t. The
sp ecied dut y cycle limit will not b e exceeded, but the actual dut y cycle may b e less than
exp ected.
F or example, Figure 8-2 sho ws the pulse output w a v eform for v arious conditions. Figure 8-2a
sho ws the pulse output when the pulse width is 500 microseconds, the dut y cycle limit is 50
p ercen t, and a v eraging is o. Under these conditions the measuremen t cycle time is ab out 3
milliseconds p er trace data p oint in the pulse prole domain, or ab out 30 milliseconds in the
frequency domain. Figure 8-2 b sho ws the same conditions with a v eraging on and an a v eraging
factor of four. No w four measuremen ts are taken for eac h data p oint with the measuremen t
cycle time alternating b et w een 1 millisecond for eac h of the measuremen ts required for the
a v eraging, and the time to mov e to the next data p oint. Figure 8-2 c sho ws the measuremen t
when 2-P ort correction is On. Here, the parameter switching time also aects the o v erall PRP
and dut y cycle.
Figure 8-2. Example Internal Pulse Output PRP and Duty Cycle
In Figure 8-2 , the pulse width is greater than the measuremen t cycle time, so the dut y
cycle could approac h 100 p ercen t. This is a v oided b y setting the dut y cycle function to the
maximum v alue allo w ed in the measuremen t. When the com bination of the pulse width
and the dut y cycle limit approac hes the measuremen t cycle time, the pulse o part of the
measuremen t cycle time is increased to satisfy the dut y cycle limit.
8-4 General Timing Information