HP 8510, User Manual

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Pulse Profile Domain
Measuremen ts in the Pulse Prole domain create a plot of the resp onse as a function of
time in sync hronization with the in ternal or the external measuremen t trigger. A rep etitiv e
sampling tec hnique is used, in whic h the data is reconstructed from samples taken from a
series of pulses. This allo ws display of the S-parameters v ersus time during the pulse. Figure
6 is an example of this pro cess sho wing a timing diagram using the in ternal pulse mo dulation
and in ternal measuremen t trigger. F or eac h pulse, a single p oint in the pulse is measured. A
prole of the pulse is made b y measuring the rst pulse at the user-sp ecied Start time, then
increasing the measuremen t trigger dela y b y a certain time incremen t for eac h pulse un til the
sp ecied n um b er of p oints is measured.
Time zero is the leading edge of the in ternally-generated pulse output w a v eform, or the falling
edge of the externally-generated measuremen t trigger w a v eform. The HP 8510 automatically
con trols the time incremen t b et w een samples, called the measuremen t resolution p erio d,
using an algorithm that dep ends up on the greater of the user-sp ecied pulse width or stop
time. This automatic selection of the time resolution can b e seen b y c hanging the n um b er
of p oints and the time span. F or narrow pulses and small time spans, the measuremen t
resolution p erio d can b e as small as 100 nanoseconds; for wide pulses and large time spans,
it can increase to m ultiples of 10 microseconds. With the in ternal measuremen t trigger,
the rst sample can b e taken up to 6 resolution p erio ds prior to time zero. When using
external triggering, the external trigger sets time zero and the rst sample can b e taken three
resolution p erio ds after time zero.
Pulse Measurements Ov erview 4-3