HP 70908A, Руководство по обслуживанию

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A djustment 08. Multiplier P ower Leveling
The microwave source sweeps a band from low to high limits . If the voltmeter indicates
an unleveled condition at any frequency , the precision DVM returns the corresponding
sweep voltage . A routine then calculates the approximate unleveled frequency and sets the
microwave source to that CW frequency . If the calculated point is leveled, the CW frequency
increments lower in 0.5 MHz steps until the unleveled condition occurs . The user then adjusts
detector bias for the particular band until the point is level (MUL T LEVEL LED turns o). (The
MUL T LEVEL LED is on the upper edge of the A10 power supply/driver .) Sweeping starts
again from a frequency 5 MHz below the unleveled point. After the initial leveling in a band,
the procedure repeats at a slower but more accurate sweep speed.
In the 2L0 and 1L0 bands , the procedure saves the detector voltages corresponding to
maximum leveled powers . T o save these reference voltages , the user connects the precision
DVM positive lead to the multiplier REF terminal pin (beneath the multiplier), the DVM
negative lead to the multiplier DET terminal pin. The user then reconnects the precision DVM
to SWEEP OUTPUT of the microwave source .
Back O P ower
A power meter sensor replaces the SYTFMD at the multiplier output, thus providing the
multiplier with a 50 ohm load. The precision DVM positive lead connects to the multiplier REF
terminal pin (beneath the multiplier), the DVM negative lead to the multiplier DET terminal
pin.
In 4L0 band, both the DUT and the microwave source tune to the low band limit, 3230.35
MHz. If the voltmeter indicates an unleveled condition because of the impedance change at
the multiplier output, the user adjusts the 4L0 potentiometer until the voltmeter indicates a
leveled condition. The user then adjusts detector bias to decrease the power meter reading
by delta P . The program saves the precision DVM reading as an indication of the leveled
frequency .
In 2L0 band, both the DUT and the microwave source tune to the low band limit, 3160.7 MHz.
The user adjusts detector bias for a precision DVM reading equal to the reference saved in the
rst part of the procedure . If the voltmeter indicates leveled power , the user adjusts detector
bias to decrease the power meter reading by delta P . The program saves the precision DVM
reading as an indication of the leveled frequency .
In 1L0 band, both the DUT and the microwave source tune to the low band limit, 3021.4 MHz.
The user adjusts detector bias for a precision DVM reading equal to the reference saved in the
rst part of the procedure . If the voltmeter indicates leveled power , the user adjusts detector
bias to decrease the power meter reading by delta P . (If range is not adequate , adjustment
of the 2L0 detector bias is permissible .) The program saves the precision DVM reading as an
indication of the unleveled frequency .
Both the DUT and the microwave source tune to the low band limit in each band in sequence .
In each band the user adjusts detector bias for a precision DVM reading equal to the reading
saved after the corresponding adjustment in the above three paragraphs .
T est
In each band, both the DUT and the microwave source tune from low to high limit. If the
power meter reading exceeds the maximum power limit, the user adjusts the corresponding
detector bias voltage for a power meter reading equal to the nominal power limit for each
band: 14 dBm for 1L0 band, 14 dBm for 2L0 band, and + 13.25 dBm for 4L0 band.
7-24 Adjustment Procedures