Agilent Technologies E4428C, User Manual

Page: 155 / 700

Chapter 4 131
Basic Digital Operation
Using Waveform Markers
segment could have different marker and routing settings.
ALC Hold Marker Function
While you can set a marker function (described as
Marker Routing
on the softkey label) either before or after
you set marker points ( page 137 ), setting a marker function before setting marker points may cause power
spikes or loss of power at the RF output.
Use the ALC hold function by itself when you have a waveform signal that incorporates idle periods, or
when the increased dynamic range encountered with RF blanking (
page 142 ) is not desired.
The ALC hold marker function holds the ALC circuitry at the average (RMS) value of the sampled points
set by the marker(s). For both positive and negative marker polarity, the ALC samples the RF output signal
(the carrier plus any modulating signal) when the marker signal goes high:
The marker signal has a minimum of a two sample point delay in its response relative to the waveform signal
response. To compensate for the marker signal delay, offset marker points from the waveform sample at
which you want the ALC sampling to begin.
NOTE
Because it can affect the waveform’s output amplitude, do not use the ALC hold for longer than
100 ms. For longer time intervals, refer to
“Power Search Mode” on page 648 .
CAUTION
Incorrect ALC sampling can create a sudden unleveled condition that may create a spike in
the RF output, potentially damaging a DUT or connected instrument. To prevent this
condition, ensure that you set markers to let the ALC sample over an amplitude that
accounts for the higher power levels encountered within the signal.
Positive: The signal is sampled during the on marker points.
Negative The signal is sampled during the off marker points.
Positive Polarity