rf signal

[abedi]

Dear Handi

Thank you for your message.I acquire the RF signal with PXI. Labview is  the software I use. For this software I am new user. I never use that before, it makes 4 week that I work with that software.

I want to buliding a block diagram to acquisition for antenna signal (433MHZ and 866MHZ). But I need to do the signal processing to the signal acquired before stored it.

The different steps are: acquire , filtering , downsampling(because i will acquire data during 24h, and I need to let pass for e.g. one data on two) and storage(so i could analyse the data stored).

But with Rf signals, I dont see the VI that do filtering downsampling and storage.  Down, you can see the block diagram I begin to do.

Thank you for your reply

[Andy_Hinde]

Hello Abedi,
Let me make a few copmments:
As for your statement, "But I need to do the signal processing to the signal acquired before stored it.", you must transfer the data to host PC RAM before you can do any software processing, so downsampling in SW will not help your PCI/PXI bus bandwidth situation. The PXI-5660 does have an onboard Digital Downconverter which performs digital downconversion to 0 Hz (baseband), filtering, and decimation to lower the data rate. This is all done in PXI-5660 hardware before the data is transferred to host PC RAM so your bandwidth limitations are reduced. The DDC is only utilized for signals with bandwidth <= 1.25 MHz, so if your signal has larger bandwidth than 1.25 MHz, the DDC cannot be used. If your signal is <+ 1.25 MHz, the DDC will be used automatically.

Thanks,
And

[abedi]

Hello Mr. Handi

Thank you for your reply, if I have understand what you wrote me, I must transfer the data acquired to PC RAM before to beginning any signal processing.

The bandwith we are choice is 2Mhz, you told me that: if your signal has larger bandwidth than 1.25 MHz, the DDC cannot be used. What can I use.

If is that, first I must build the block diagramm for aacquisition. In this case, I want to do acquisition during 24h but I dont want to acquire all the the signal who pass, how can I do to acquire one sample one two?

Second I must build the block diagramm for signal processing. In this case, I use the DAQ?

Please in your reply can you give me some example?

Thank you very much