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FMCOMMS1-EBZ REVC using Matlab for transmitting and agilent signal analyzer for receiving

Question asked by hxm934 on Apr 26, 2015
Latest reply on May 1, 2015 by dpu

Fellow engineers,

 

I am trying to use Matlab/Simulink to transmit random data using Bernoulli Binary Generator which is then fed to a normal raised cosine filter and afterwards it is sent to the SDR Transmitter.

Note: All the blocks and the parameters used are attached in the following figure "Setup Matlab.jpg".

 

To receive the signal, I have directly connected the transmitter of the FMCOMMS1-EBZ to the agilent CXA N9000A signal analyzer in order to view the acquired I and Q signals.

 

The value of center frequency at the FMCOMMS1 in Matlab is set at 2.15 GHz.
I am setting the value of the Center frequency in the signal analyzer by first looking the peak frequency in spectrum analyzer mode and then entering the same peak frequency as the center frequency in the IQ analyzer mode.
The usual signal output should look something like the signal shown in attached figure "Matlab Output.jpg".

 

But what I see in the signal analyzer is really different.

When I viewed the signal for 2 ms it looked as shown in attached figure "Screen1 2ms 0.jpeg".

But when I viewed the signal in a 50ms window, I see the signal as attache in the figure " Screen1 50ms.jpeg".

 

Now in the figure with 50ms window, we can clearly see the raised cosine outputs, but they seem to have a sine wave type envelope. I just don't understand the reason behind that. I have tried changing center frequencies to some near by values and even then, this type of sine envelope doesn't go away.

Can you help me figure out the reason behind that, so that I can properly decode the signal back in Matlab after capturing, which currently I am not able to perform.

 

I even tried running the QPSK example on the Mathworks website. Even that shows the similar result.

 

Thank you for your support.

 

Regards

Himanshu

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