Pulse Repetition Period And Duty Cycle Considerations - HP 8510 User Manual

Pulse Repetition Period and Duty Cycle Considerations

From this information it can be seen that the pulse repetition period and thus the duty cycle
of the pulsed-RF signal applied to the DUT can vary depending upon the instrument state.
For measurements in which the PRP or duty cycle is not important, simply set the pulse
width and the duty cycle controls to an appropriate value and make the measurement. The
speci ed duty cycle limit will not be exceeded, but the actual duty cycle may be less than
expected.
For example, Figure 8-2 shows the pulse output waveform for various conditions. Figure 8-2a
shows the pulse output when the pulse width is 500 microseconds, the duty cycle limit is 50
percent, and averaging is o . Under these conditions the measurement cycle time is about 3
milliseconds per trace data point in the pulse pro le domain, or about 30 milliseconds in the
frequency domain. Figure 8-2b shows the same conditions with averaging on and an averaging
factor of four. Now four measurements are taken for each data point with the measurement
cycle time alternating between 1 millisecond for each of the measurements required for the
averaging, and the time to move to the next data point. Figure 8-2c shows the measurement
when 2-Port correction is On. Here, the parameter switching time also a ects the overall PRP
and duty cycle.
Figure 8-2. Example Internal Pulse Output PRP and Duty Cycle
In Figure 8-2, the pulse width is greater than the measurement cycle time, so the duty
cycle could approach 100 percent. This is avoided by setting the duty cycle function to the
maximum value allowed in the measurement. When the combination of the pulse width
and the duty cycle limit approaches the measurement cycle time, the pulse o part of the
measurement cycle time is increased to satisfy the duty cycle limit.
8-4 General Timing Information