NI PXIe-5694 Calibration Procedure
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© National Instruments
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39
16. Set the NI 5622 digitizer DDC center frequency to the RF source 1 frequency.
17. Acquire a record of complex samples with the NI 5622 digitizer and compute the
digitizer
power
using the following equation:
where:
N
= Number of samples to acquire
I
j
= Real part of the
j
th complex sample
Q
j
= Imaginary part of the
j
th complex sample
18. Query the NI 5622 frequency response and retrieve the value at the current DDC center
frequency by using linear interpolation.
19. Calculate the NI 5694
gain
using the following equation:
Gain
=
Digitizer Power
+
Digitizer Cable Loss
-
Digitizer Frequency Response
-
Input Power
Note
Refer to Table 5 for the characterized digitizer cable loss.
20. Record the calculated gain and the current frequency of RF source 1 to the NI 5694
EEPROM.
21. Repeat steps 13 through 20 for all the values in the frequency list computed in step 12.
22. Repeat steps 11 through 21 for IF attenuation table index values from 1 to 25, with a step
size of 1.
23. Repeat steps 10 through 22 for each of the following IF filter values:
•
5 MHz
•
1.4 MHz
•
400 kHz
•
110 kHz
24. Reconfigure the NI 5694, enabling step gain.
25. Reconfigure RF source 1 for a power level of -15 dBm.
26. Repeat steps 10 through 23 with the new settings.
27. Reconfigure the NI 5622 digitizer, disabling the bandpass filter.
28. Reconfigure the NI 5694 as follows:
•
Step gain: Disabled
•
IF conditioning downconversion: Enabled
29. Repeat steps 10 through 23 with the new settings and the following changes:
•
In step 16, set the DDC center frequency to 215 MHz -
RF Source 1 Frequency
•
In step 23, add 30 kHz to the list of frequencies to measure
30. Reconfigure RF source 1 for a power level of -25 dBm.
31. Reconfigure the NI 5694, enabling step gain.
Digitizer Power
10
log
10
×
1
N
----
I
j
2
Q
j
2
+
(
)
j
0
=
N
1
–
10
+
=
