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NI PXIe-5694 Calibration Procedure
12. Acquire a complex record with the NI 5622 digitizer and compute the
digitizer power
in
dBm 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
13. Query the NI 5622
digitizer frequency response
and retrieve the value at the DDC center
frequency by linear interpretation.
14. 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.
15. Record the calculated gain and the RF input frequency value to the NI 5694 EEPROM.
16. Increase the RF source 1 frequency and the digitizer DDC center frequency by 1.6 MHz.
17. Repeat steps 10 through 16 for all frequencies up to and including 267.5 MHz.
18. Close the IF attenuation calibration step.
19. Close the external calibration session.
Adjusting IF Gain
Complete the following procedure to measure and adjust the IF gain performance of the NI 5694
IF conditioning module.
1.
Zero and calibrate the power sensors using the built-in functions in the power meter.
2.
Ensure that the hardware is properly configured as described in
.
3.
Run the self-calibration procedure of the NI 5622 digitizer.
4.
Initialize an external calibration session for the NI 5694.
5.
Initialize an IF attenuation calibration step.
6.
Configure the NI 5694 as follows:
•
Signal conditioning: Enabled
•
Reference source: PXI_Clk
•
IF conditioning downconversion: Disabled
•
Step gain: Disabled
Digitizer Power
10
log
10
×
1
N
----
I
j
2
Q
j
2
+
(
)
j
0
=
N
1
–
10
+
=
