Agilent Technologies 85025A, User'S And Service Manual

Page: 27 / 98

Measurement System Conguration
With an 8757 series scalar network analyzer using an 85025A/B/D/E detector ,
system conguration requires special attention. A C mode is the default state
of the analyzer system and there are no further requirements to initiate a
measurement. However , to enable DC mode operation, a series of keystrokes is
required.
DC Detection mode
DC detection oers greater power measurement accuracy and the ability to
characterize oscillators and modulation-sensitive devices . Figure 3-2 depicts a
typical measurement setup for 0.01to 50 GHz, using an Agilent 8350B sweep
oscillator/RF plug-in as the source .
1 . On the analyzer , press 4 PRESET 5 . Connect the detector(s).
2. DC detection mode must be selected. On the analyzer , press 4 SYSTEM 5 and
select
NNNNNNNNNNNNNNNNNNNNNNN
MODE DC .
When the
NNNNNNNNNNNNNNNNNNNNNNN
MODE DC softkey is selected, the source's square wave modulation
is automatically switched OFF .
A ccurate DC Measurements
Zeroing the Detector
When you make DC detection measurements , it is important to perform this
detector zeroing procedure to compensate for the eects of DC drift and
temperature uctuations . This zeroing procedure eliminates small DC voltages
from the diode detector that would otherwise cause amplitude measurement
errors at low (40 dBm) power levels . Zeroing also establishes the displayed
noise level with no RF signal applied (the system's noise oor).
A utozero
Pressing the autozero softkey
NNNNNNNNNNNNNNNNNNNNNNN
AUTOZRO switches OFF the source RF signal
output and automatically zeros the detector .
Agilent 85025A/B/D/E Operation 3-3