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.