AM Signal

[JerryAL]

Hi

I’ve checked your attached code, but there is no LV FPGA code in the zip files.  I’m also worried that you may not be using the NI 5640R module properly.  There are a few ni5640R Vis missing the Host VI that are required to configure the DACs on the IF-RIO.  Especially the Interpolation factor/IQ rate as well as downloading a waveform containing the baseband signal for modulation.

I suggest that you read the “Getting Started with the “NI PCI-5640R IF Transceiver and the LabVIEW FPGA Module”.  I suggest trying the example as well as learning how to resave one of the shipping examples that you can use as a base to start your application.

There is an attached example above, (example.zip) that has a very basic AM modulation in it from data generated on the fly.  The FPGA code can be expanded to include the parameter you wish to adjust, and on the fly, from the host.  You can look at one of the shipping examples to see how to transfer a waveform from the host to the FPGA VI.

Jerry

[IF-RIO]

Hello Sandeep

This is Rajesh, regarding the generation of AM Demodulation(example.zip) in NI 5640R, we did it sucessfully and verified it using Spectrum Analyzer.
We thank for your support.
Earlier using only labview , we designed all modulations in a  logical ( like adders and multipliers, cosine, sine) way. Yet now in example.zip i.e. for
"AM demodulation using FPGA 564R0 target", the method of generating AM Demodulation is entirely Different.
My question is that can we develop the logic that is "developped using only labview(without FPGA)"  in the Labview-FPGA.
Because we have developped all the modulations and PSK's in Labview(without FPGA), Now We need to Develop those using Labview-FPGA.
Help Me in this context.

With regards

Rajesh G

[IF-RIO]

The logic behind the AM Demodulation(exapmle.zip downloaded from the forum ) is not getting for us, at the same time we are not able to understand the modulation logic you are using for demodulation. Help me in this context.

[JerryAL]

Hi Rajesh

Oops.  Sorry, it’s been a while since that was posted.  I thought it was another example that showed a basic implementation of AM Demod in the FPGA.  This example brings the IQ data up to the host before the demodulation.

An AM signal is generated simply by sending data to the DAC that only has an I component.  Q is all zeros.  This creates a very basic AM waveform for the demodulation part.

A simple case of AM demodulation can be done by implementing in the FPGA: |Xc(k)| = Root( Xi(k)^2  + Xq(k)^2 ).  The envelope of the AM signal being equal to the magnitude of Xc(k).  You can find more information on this in Understanding Digital Signal Processing by Richard G. Lyons.  Second Ed. Page: 366.  I believe this is implemented in the Host VI of the example.zip files.

For an FGPA, the hard part is the square root.  There is an example implementation that can be found here:
http://zone.ni.com/devzone/cda/epd/p/id/2908

The signal will have to be sent through a FIFO to a normal while loop where the square root takes place and then up to the Host if that is what you wish.  The normal clock for everything else is running off of the configuration clock at 20 MHz.  Depending on your IQ sample rate, you may need the normal while loop running at a faster clock rate.  You can change the source of the configuration clock in the project to be the RTSI clock, and configure the RTSI clock to run at 50 MHz or even 100 MHz, depending on your code implementation.

Jerry

[IF-RIO]

Hello Sandeep

This is Rajesh, here we are posting our query regarding the generation of AM Modulation using Labview-FPGA NI 5640R card. We have Done the AM DeModulation successfully and we also checked it using Oscilloscope. With the reference of the AM Demodulation we are now trying to do the AM modulation and thus we are generating only the Carrier wave at 21.4 MHz at our desired frequency but unable to check the AM Modulated Envelope. We are attaching our code to this message.
Help us in this context to be able to check our AM envelope in the Oscilloscpoe.

With regards

Rajesh G

[IF-RIO]

Hello
This is Rajesh. We have Both The AM Modulation and Demodulation Successfully and verified it using Oscilloscope.
Now we are doing for all kind of Modulations.
We thank for your Support.

With Regards

Rajesh
rajeshg@icsglobal.biz

[IF-RIO]

hello,
Rajesh here,   i m tring to do the  basic Fm modulation Generation at 21.4 MHz with the help of the FPGA PCi-5640 R .
please help me to get the FM modulated  output as i desired and also that, i want to capture it on external Oscilloscope...

thanks .

[IF-RIO]

hello ,

rajesh here
as  i have done  the Am modulation
i want to know that can i give same signal as a input to analog input port what i am getting through the output port from the card,if yes, how can i do that. how can i get the signal and,
2)  i want to get the Polyphase FFT of the input signal, for this wt i have to use and how to get that FFT plot.

plz help me out for both the quries

[IF-RIO]

Hello,

I have done the Am modulation with pci 5640R, now i want to generate the Side bands (Upper side bands, Lower side bands).
How can i get these bands with PCI 5640R and how can i check with Extrenaly Signal analyser

Please help me out ASAP.

Thanks.

[IF-RIO]

Hello Mr. troy,

1) I used ur Example.zip for the Am modulation, i got the Am Modulated signal with the power spectrum, but that spectrum is not according to the Receice Frequency, how can i get that according to the Receive requency.

2) Second this i am not able to get the side bands also in that Power spectrum,only single Spectrum is coming, how can i get the side bands also.

3) Third things is that what is the use of "Test out frequency" there, because if i changed the Test out frequency there is no change in the Output waveform.

4) can i get the Side bands individualy(LSB,USB) on the output side and can i get these through the DAC0 or DAC1 for the External Oscilloscope.

Please help me out to understnad Better working

Thanks n Regards