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Capturing IQ data from EXA

Question asked by maxplus on Feb 20, 2018
Latest reply on Mar 15, 2018 by maxplus

I'm trying to pull IQ data out of an EXA N9010B for post-processing. I've managed to capture the I/Q samples and dump them to a file and analysed its FFT spectra.  The signal is a LTE, QPSK in a 20MHz signal generated by Signal Studio.

 

I used Excel (limited to 4096 FFT points) to display the FFT spectra.

It appears that it is not correct.

1. I was actually expecting a LTE signal in 20MHz bandwidth after applying FFT.  On  the spectrum analyser, it actually displays a LTE 20MHz signal. 

2. The frequency component is wrong - it should be 28GHz. 

 

Can anyone help me where I am going wrong?  Is it related to the EXA settings?

The sampling time and number of samples of the EXA are:

Sample time       7.33333E-07

No of Samples   2728

The EXA have not got the VSA enabled to measure EVM.  So, I thought capture the IQ data and analyse it in math tool such as Excel to calculate EVM. 

 

 

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