the signal of 5641R stream from Disk could not be demodulated rightly

[xk104@sina.com]

Hi ,

I made a IQ file,which is a signal with PN9,Gray QPSK ,the file is OK, IQ rate of Sampler is 3.75MHz

I use the example of 5641R Driver,"5641R stream from Disk ",to transmit the IQ FIle , frequency is 20MHz , IQ rate for DAC is 3.75MHz

on the AO Port, I got the Spectrum of the signal ,it is good.but , when I demodulated the the signal of the AO port, the result is not good ,it is not the PN9.

what is the reason? Who can help me for it ?

thanks!

[JVP · Accepted solution]

Hello,

I have few questions for you:

1. Could you tell us how you recorded the original file?
2. Did you use the "5641r stream to Disk" example?
3. Would it be possible for you to attach the recorded file to this forum?
4. To create the PN9, Gray QPSK, signal did you use the NI Modulation Toolkit?
5. Are you reading back the signal on the 5641r AI channel?
6. If not, what is the source you are reading back the signal on?
7. You mentioned that your IQ rate is 3.75 MS/s, is this correct?
8. What is the Center Frequency?

Best Regards,

Jignesh P

Applications Engineer

[xk104@sina.com]

Hello JVP:

Thanks for your response.

I haved solved that problem. It was that the actual IQ rate was not equal to the vaule of My Setting.

I used NI5661 recording file. and the source was Agilent   ESG.

Now ,I have another problem. Maybe I need your help later.

Thanks again.

charles