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Chapter 3: Testing Performance
To test bandwidth
3–14
7
Select V
amptd
from the Voltage submenu of the Measure menu.
8 Note the V
amptd (1)
reading at the bottom of the screen. V
10MHz
=_______________mV.
9 Set the power meter Cal Factor % to the 10 MHz value from the calibration chart on
the power sensor. Then press dB[REF] on the power meter to set a 0 dB reference.
This establishes the baseline output power at 10 MHz as a reference for the bandwidth
measurement.
10
Change the signal generator output frequency to 1000 MHz for Agilent 54835A,
1500 MHz for Agilent 54845A, or 2250 MHz for Agilent 54846A. Set the power meter
chart Cal Factor % to the 2250 MHz value, to the 1500 MHz value, or to the 1000 MHz
value depending on the model number.
This step compensates the power meter reading for changes in the power sensor output at
1000 MHz, 1500 MHz, or 2250 MHz with respect to 10 MHz.
11
Adjust the signal generator output amplitude for a power reading as close as possible
to 0.0 dB[REL]. Write down the actual reading. Reading = ______ dB [REL].
The reading on the power meter will be used to correct the final bandwidth value.
12
Use one of the following steps depending on the Infiniium oscilloscope model being
tested and the bandwidth acquisition mode:
a (Use this step for model 54835A 1000 MHz Equivalent Time bandwidth check.)
Set the sweep speed to 500 ps/div using the Horizontal sweep speed knob.
b (Use this step for model 54845A 1500 MHz Equivalent Time bandwidth check.)
Set the sweep speed to 50
µs/div using the Horizontal sweep speed knob.
c (Use this step for model 54846A 2250 MHz Equivalent Time bandwidth check.)
Set the sweep speed to 50
µs/div using the Horizontal sweep speed knob.
d (Use this step for Real Time bandwidth checks: 1000 MHz on 54835A, 1500 MHz on
54845A, or 2250 MHz on 54836A)
Set the sweep speed to 500 ps/div using the Horizontal sweep speed knob.
e (Use this step for 1 M
Ω, 500 MHz bandwidth check for all three models.)
Set the sweep speed to 1 ns/div using the Horizontal sweep speed knob.
13
Press the Clear Display key followed by the Run key to display a trace. (It there is no
trace on the screen slowly adjust the Trigger Level knob through zero until a trace is
displayed.) Note the V
amptd(1)
reading.
V
2250MHz
= _______________ mV (54846A)
V
1500MHz
= _______________ mV (54845A)
V
1000MHz
= _______________ mV (54835A)
14 Calculate the response using the formula:
For example:
15
Correct the result from step 14 with any difference in the power meter from step 11.
Observe signs. For example:
Result from step 14 = -1.19 dB
Power meter reading =
−0.5 dB(REL)
then true response = (
−1.19)−(−0.5) = −0.69 dB
(__________)
− (__________) = _________dB
16 The result from step 15 should be between +3.0 dB and −3.0 dB. Record the result in
the Test Record.
17 Switch the power splitter from the channel 1 to the channel 2 input.
18 Turn off the current channel and turn on the next channel using the channel keys.
response dB() 20log
10
V
1500 MHz
V
10 MHz
------------------------
20log
10
________=_______dB==
20log
10
487 mV
559 mV
-------------------
20log
10
0.871 1.19dB–==