Agilent Technologies 85309B, Руководство пользователя

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1-10 Service Guide 85309-90082
Getting Started LO/IF Distribution Unit
Step 6. Adjust the LO Power 85309B
Step 6. Adjust the LO Power
The procedure below is applicable to all 85309B models, and assumes the user has basic knowledge on the
antenna test system. To learn about the various antenna test systems, refer to the
Agilent Antenna Test
Selection Guide , part number 5968-6759E. See “Printing Copies of Documentation from the Web” in the first
section of this manual.
The front panel of the 85309B has a DETECTOR VOLTAGE window, an LO POWER ADJUST mechanism, and
an LO POWER OUT OF RANGE LED. Refer to
“85309B Front Panel Features” on page 2-3 . The value shown in
the DETECTOR VOLTAGE window is the voltage coming from a power detector in the reference mixer. The
voltage is directly proportional to the amount of LO power arriving at the mixer. A label on the reference
mixer shows the precise voltage which corresponds to the power at the mixer's LO input. In the procedure
below, you adjust the LO POWER ADJUST so the DETECTOR VOLTAGE display matches the voltage on the
mixer label.
Once set, the ALC loop will maintain the desired LO power level regardless of LO frequency. Repeat the
procedure below only if you change one of the mixer modules or the LO source.
Find the detector voltage value written on the reference mixer. Record the value in Table 1-1 below.
Procedure
1. Set the LO source power to 6 dBm.
2. Observe the voltage displayed in the 85309B’s front panel DETECTOR VOLTAGE window.
3. Adjust the 85309B’s LO POWER ADJUST mechanism until the voltage displayed in the window is equal
to the voltage written in Table 1-1 (also shown on the reference mixer label). If the LO POWER OUT OF
RANGE LED is lit, there is an unleveled ALC state. To fix the problem, refer to “LO POWER OUT OF
RANGE” on page 2-4 . Note that due to the long LO cable length (the RF cable between the LO source and
the 85309B) you must compensate for cable loss by increasing the LO source power.
NOTE The voltage displayed in the DETECTOR VOLTAGE window varies with frequency. This is
normal. The LO POWER OUT OF RANGE LED is lit only if the system's automatic leveling
loop cannot level the voltage sufficiently. This can happen if the LO source is disconnected,
or if more power is needed than the 85309B unit can supply for a given frequency range.
Table 1-1 Value Indicated on the Reference Mixer
Parameter Value
mV (typically –40 to –80):