Positive and Negative Frequency deviation Calculation

[Frabto]

Hi ,

    Iam using PXI 5600 with PXI 5620 for RF measurement.

    I need to measure Positive and Negative frequency Deviation. The NI example vi "MT RFSA Demodulate FM.vi" gives peak Frequency deviation . Can any one please help me to find positive Frequency Deviation and Negative frequency deviation from it

Thanks,

Niju.

[P.Sanders]

What have you tried so far?

[Andy_Hinde · Accepted solution]

Hi Niju,

First things first - the 5600+5620 combined is what we refer to as a PXI-5660 RF Signal Analyzer.

The PXI-5660 cannot be progammed via the NI-RFSA driver. The Modulation Toolkit FM example you reference is for the PXI-5661 and PXIe-5663 analyzers, both of which use the NI-RFSA driver.

You should use MT ni5660 Demodulate FM.vi, located under ni5660 examples.

Now on to your question...

When you perform an FM demodulation, the resultant data out of the MT Demodulat FM subVI is frequency vs. time, with the frequency (Y axis) values being relative to the specified carrier frequency. So, the data is frequency deviation (Hz) vs. time. All you need to do to get positive and negative frequency deviation is to use a LabVIEW Array Max & Min primitive from the Array functions pallette. This will give you the min and max value of the FM data which will be the peak negative and peak positive frequency deviation.

Regrds,

Andy Hinde

RF Systems Engineer

National Instruments

[Frabto]

Andy ,

    Thanks for the detailed information. As  Iam a newbie to this RF stuff I was confused.

         Thanks a lot!!!