Demodulate Satellite signal

[schtrumph]

Hello,

I use the NI PXI-5660, and I need to demodulate a signal (same as a satellite signal Frq: 1450MHz Symbol rate from 22 to 33 MHz), but I have a bandwith problem (limited to 20MHz) I try to change the filter to decrease the bandwidth, but I still have the same problem.

I need to mesure the BER and have the IQ Constellation to manage a terrestrial MMDS transmeter.

Is there any filter or other kind of solution to demodulate this signal?

Thanks for your help

[Yardov]

Hi Schtrumph,

As you well said, the NI PXI-5660 has a real time bandwidth of 20 MHz. This means that you will not get your entire signal bandwidth since your symbol rate is 22 to 33 MHz at the same point in time. I am unsure on what do you mean by decreasing the bandwidth, you mean your signal bandwidth? or the 5660? If you decrease your symbol rate, you can reduce the bandwidth but if you filter the signal, then you will loose information and probably the entire signal.
The only solution, with the information given here, is to reduce your signal bandwith by reducing the symbol rate.
Hope this helps,

[schtrumph]

Thank for your reply;

The problem is that we use symbol rate between 22 000 and 33 000 Ms/s.

So it's impossible for me to manage the quality of my signal with the NI 5660 (found the BER for example)...

[Andy_Hinde]

Hello Schtrumph,
As Gerardo and you mentioned, the real-time bandwidth of the PXI-5660 is 20 MHz.

If your signal is wider in bandwidth than 20 MHz, and you need to acquire vector data (IQ data) containing phase information for the purposes of demodulation, then you cannot use the PXI-5660. Retuing the PXI-5660 to capture the other portion of your signal would make the two portions of the signal discontinuous in time, as well as make the phase information between the two captured segments unrelated. Unfortunately, there is no workaround in this case - the bandwidth of your signal is simply wider than the bandwidth of the input device.

Regards,
Andy Hinde
National Instruments