HP 8340B Manual page 74

4-15.
AMPLITUDE MODULATION TEST (Cont'd)
NOTE
It
is
important that the mixer be connected
directly to the LO's RF Output
connector.
Procedure
AM SENSITIVITY AND ACCURACY
1.
Connect equipment as shown
in
Figure 4-19. Connect
the mixer LO port at the LO's RF output.
Connect the Power Sensor to the power meter. Allow
a one hour warm up time.
Set
the
power
meter's calibration factor switch to include
1.5
GHz, then zero and calibrate the
power meter.
Connect the power sensor to the DUT's RF
output.
2.
On the DUT, press [INSTR
PRESET] [CW] [1]
[.]
[5] [GHz].
Press
the
[POWER LEVEL]
key and
enter
[-]
[5] [dBm].
NOTE
The function generator output impedance
is
50 Ohms and
its output
indi¬
cation
accuracy assumes a
50 Ohm load. The DUT's
AM input
imped¬
ance
is
600
Ohms; therefore,
a
high
impedance
DVM
is used to measure
and set the
function generator output level.
3.
Zero
the
power meter as follows:
With
power applied to the sensor, press the
power meter RANGE HOLD. Press the DUT's [RF]
key to
turn
the RF OFF. Zero the
power
meter. Press the [RF] key to turn
the
RF
ON.
4. Using the DVM
as an indicator, set the function generator
to output
0
Vdc (If the function gener¬
ator
being used
does
not have this
feature, use a
dc
power
supply).
Press the DUT's
[AM]
key
(AM
ON).
Note the power meter
indication.
5.
Simulate
+ 30%
modulation by setting the function
generator
output to +
0.3
volts dc as indicated
on the DVM. The power meter indication should increase by 2.18
to
2.38 dB from the value noted
in
step 4.
20 log
(1
+
(0.3
-
(0.05 times 0.3)))
=
2,18 dB
to
20
log (1
+
(0.3
+ (0.05 times 0.3)))
=
2.38
dB
6.
Simulate —30% modulation by setting the
function
generator output
to
—0.3
volts dc as indicated
on
the DVM. The power meter
should
decrease
by
2.91
to 3.29 dB from
the value noted in
step
4.
20
log
(1
+
(-0.3
-
(0.05 times -0.3)))
=
-2.91
dB
to
20 log (1
+
(-0.3
+
(0.05 times -0.3)))
=
-3.29
dB
NOTE
The DUT's test power levels
are
selected to avoid power
meter range
changes at the
+30
and —30% modulation
settings.
HP 8340B/41B
Performance Tests
4-73