NI Home > Community > NI Discussion Forums

Digital I/O

Reply
Member
hass123
Posts: 8
0 Kudos

acquiring I/Q data from sound vi and then seperating it in I and Q

hye, i am basicaly working on sdr, i am using softrock lite 2 (http://www.wb5rvz.com/sdr/sr_lite_ii/) as reciever which downconverts the incoming signal in I and Q data and provide it as an input through microphone as left and right, i am using acquire sound vi  to take input from microphone in labview, but the question is how i can split it inti left and right channel or I/q data inside labview developing environment. Please help as soon as possible, your answers will be appreciated.

Regards

Member
TrottM
Posts: 91
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

Where have you got to at them moment with this? Have you got a stereo signal from your microphone into labview or have not managed to get that far. It sounds like you just need some array manipulation to seperate you L&R channels from your stereo signal but without you showing us what you have got so far its hard to say.

 

Show us where you have got to so far and we would be happy to point you in the right direction.

Matthew Trott
Applications Engineer
National Instruments UK
www.ni.com/ask
Member
hass123
Posts: 8
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

well here in the attachment is the VI i am working on, i am basically trying to build am reciever, and softrock provides stereo output, i am acquiring that data through acquire sound vi, i am trying to split I/Q data using split function and then demodulate it. please have look into it and let me know.

Regards

hass

Member
TrottM
Posts: 91
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

Ok first things first the dynamic data type is not helpful to what you want to do so you need to first of all convert your aquired data to a 2d array of scalers using the 'convert from dynamic data' vi. Once you have your array one colum will be I and the other will be Q. You can seperate this out using the 'Index Array' function. You then should have 2, 1D arrays. one for I and one for Q. Hopefuly that answers your question.

 

If you need help with these function I suggest you have a go first and read the help file for each of them first. This is done by pressing ctrl+H and hovering over the relevant Icons.

Matthew Trott
Applications Engineer
National Instruments UK
www.ni.com/ask
Member
hass123
Posts: 8
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

thanx Matthew, so far i have understand how to seperate it in to two arrays, attached is the vi i have made. Since I/Q data have phase difference of 90 degree, but i can not find it here. please tell me how can i find out the phase difference among the two. i am using extract tone function but it is not giving the perfect answer.

Regards

hass

Member
TrottM
Posts: 91
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

It appears to me that the data being aquired from your microphone is not what you expect it to be then. What I have explained is how to seperate the audio out. How are your input and what makes you think that L&R is I&Q?

Matthew Trott
Applications Engineer
National Instruments UK
www.ni.com/ask
Member
hass123
Posts: 8
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

well softrock provides I and Q as output through stereo, so thats y i expect that stereo channels that is left and right will be I and Q data.

Member
hass123
Posts: 8
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

here is the diagram of softrock circuit, in the bottom right you can see it provides I and Q data as left and right audio channel.

Member
TrottM
Posts: 91
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

have you had to consruct this circuit or has it been made for you. Are you sure this is working correctly. Would it maybe better to aquire the I and Q signals seperately using DAQ functions or are you limited to through a microphone because of hardware.

 

If you are using the microphone port through your computer be aware that the sort of data you get from this may have been altered by the audio circuitry.

 

I think it would be better if you used DAQ functions and dedicated acquisition hardware for this.

Matthew Trott
Applications Engineer
National Instruments UK
www.ni.com/ask
Member
hass123
Posts: 8
0 Kudos

Re: acquiring I/Q data from sound vi and then seperating it in I and Q

can DAQ be configured for this device???

Regards