To Analyze A Transient Signal With Time Gating - Agilent Technologies 89410A Operator's Manual

Characterizing a Transient Signal

To analyze a transient signal with time gating

This procedure assumes that the steps in "To set up transient analysis"
have been performed. If not, do so before continuing.
1.
Turn on time gating, set the gate length, and set up the knob to move the gate:
Press [ ], [
gate on
Time
Press the [
Marker|Entry
2.
Rotate the knob to move the gate over the very first part of the transient signal
appearing in the lower trace; see the plot below.
3.
Set up the marker to show the movement of the spectrum's peak:
Press [ ], [
A Marker Function
Press [ ], [
Shift Marker⇒]
4.
Now, move the time gate across the transient signal's time display (by turning
the knob) and note the movement of the spectrum peak:
Press [ ], and make sure [
Time
Press [ ] if the knob's "Entry" LED is not on.
Marker|Entry
Rotate the knob, moving the gate further to the right into the transient
signal and stop long enough for the spectrum to update. Then move it
again and stop. The reference marker (square) remains at the location of
the "transient start up" making it easier to see the carrier movement as
the regular marker (diamond) tracks the peak. Marker readouts in the
display pictured below show that early in the transient there is as much
as 1.00 MHz variation in carrier frequency.
With time gating on, the spectrum shown (top) is that of the data inside
the gate markers (bottom). In this case, moving the time gate across the
time signal (bottom) shows that the carrier frequency varies with time
(the spectral peak moves). We can use FM demod to show this, too.
(grids were turned off in the illustration to highlight the gate markers.)
3-4
], [ ], 3, [ ], [
gate length
us
] hardkey so that the knob's "Entry" LED is on.
], [ ].
peak track on
(turns offset marker on and zeros it).
] is selected (if not, press it).
ch1 gate dly
].
ch1 gate dly