HP 8340B Manual page 314

5-17.
RF
OUTPUT POWER FLATNESS ADJUSTMENT (Cont'd)
Procedure
1.
Calculate
a
correction factor for the HP
8485A Power
Sensor as follows:
Find the
CAL FACTOR end points (0.05
GHz
and
the maximum DUT RF Output frequency) by
either using
a
calculator to
find the
best straight
line approximation
to the
CAL FACTOR curve
in
percent or by using
a
straight edge for the best straight line
approximation
on the
CAL FACTOR
curve located on the body of the power
sensor.
Convert both
end points to dB using the following equation:
Endpoint
(dB)
=
-10log(endpoint(%)/100)
Calculate the slope as follows:
HP 8340B:
Slope (dB/GHz)
=
[26.5
GHz
Endpoint
(dB)
-
0.05 GHz Endpoint (dB)]/26.45
HP 8341
B:
Slope
(dB/GHz)
=
[20
GHz
Endpoint (dB)
-
0.05
GHz
Endpoint (dB)]/19.95
2.
Connect the HP 8485A power sensor to the power meter and then
turn the
DUT's and the power
sensor's LINE
switches
ON. Connect the oscilloscope as shown in Figure
5-61. Allow
30 minutes
for the equipment to warm
up.
3.
Calibrate and zero the power meter. On the OUT, press [INSTR PRESET]
[CW] [4]
[.]
[5] [GHz]
and then
[RF]
to turn the RF
off.
Zero the
power meter. To ensure that the
power meter
is
properly
zeroed, select
WATT mode,
and press the
ZERO
button until
the
power meter
indicates
<
0.02
on
the most sensitive range. Select the dBm
MODE
on
the power meter.
4.
On the DUT, press
[INSTR PRESET] [START] [2]
[.]
[4] [GHz].
Press
[POWER LEVEL] [0] [dBm]
[SWEEP TIME] [5] [sec].
Press [SLOPE], enter the slope calculated in
step
1,
and terminate the
entry by pressing [dBm]. Save this
instrument state by pressing
[SAVE]
[1].
5.
Set the oscilloscope to
A
vs
B.
Set the horizontal
sensitivity
(CHAN B) for
1
V/Div and the vertical
sensitivity
(CHAN A)
for
0.1
V/Div.
Adjust the oscilloscope's vertical position control to
center the
trace on the oscilloscope. Adjust the horizontal position
control to display the entire trace.
6.
On the
DUT, press [INSTR PRESET] [CW] [1] [4] [GHz] [SHIFT] [POWER LEVEL] [.] [0] [5]
[dBm] [POWER LEVEL] [-] [1] [dBm]. Press RANGE HOLD
on the
power meter
and set the CAL
FACTOR
% dial
for the
14
GHz CAL FACTOR
indication on
the power sensor.
7.
Using the DUT's front panel rotary knob (RPG), increase the power
level
until
the power meter
indicates
0
dBm. The output power sensitivity on the
DUT
is
0.05 dBm so adjust
the
power
level
for the closest reading to
0
dBm
if you cannot adjust
for exactly
0
dBm.
8. Adjust the
oscilloscope's CHAN A
position control to place the dot on the center horizontal
graticule.
Determine the dB/Div sensitivity of the oscilloscope by rotating the
DUT's
rotary knob
until the
dot
is 1
major graticule above the
center graticule.
Determine the sensitivity by reading the
power
level on the power
meter.
Repeat
this
process and determine the sensitivity for the second
major graticule above the center graticule and the two major divisions below the
center graticule.
Once the oscilloscope is calibrated in
this
manner, you can use
the oscilloscope's display to
determine
the
power flatness of the trace. The
scope should now be set up for
2.4 GHz/Div (X-
Axis) and approximately 0.4 dB/Div
(Y-Axis).
5-116
Adjustments
HP 8340B/41B