Real and complex acquisition

[madd]

   Hello

1- using 5142 I can acquire real and complex data what does that mean.  if  x(t)=cos(theta)+jsin(theta). Then real acq mean acquiring cos(theta) and complex means acquiring. cos(theta)+jsin(theta) is it so? if it is i want to acquire only Real(I) cos(theta) of my signal what settings of 5142  should i set (in property node for DDC etc).

2- Does Frequency translation  enable always make coming signal complex. Or in real mode only I(phase) is mixed with coming signal and in complex mode I(phase) and Q(phase) are mixed. I have been told to see OSP Ex downconversion example. But confusion is freq translation is enabled there. So I am confused that we have set acq mode to real then we are doing frequency translation doesn't it make signal complex. And out of that complex(array) we are getting real(array) in fetch vi. Can't I make it purely  Real(I)Or it is not possible to acquire real(I). I should always have to acquire complex then get real out of it.

3 -could u please generate a cosine signal of 20Mhz using Real generator 1Vpp and show me some plots at 100Ms/s and 50MS/s for real and complex acq both with 1MHZ recods to fetch.

Regards

Madd

[Aaron_W.]

Madd,

You will want to be using the Example for OSP Quadrature Downconversion.vi. There is a property for the niScope that is called "Data Processing Mode" in the example you can set it to complex or real and that will give you either component depending on how you set it in your block diagram. If you need more information on the property the context help and detailed help gives a good description of each. 

Freq. Translation does not make the signal complex.  I would recommend looking in the High-Speed Digitizers help. There are two channels, and if you decide to use both channels then you will be getting real and complex data, if you choose to use only one then you can just get the real data. This is all mentioned in the NI High Speed Digitizers Help under the 5142 device, under Onboard Signal Processing. 

[Chris_W.]

Hello Madd,

Because your question on this post is the same as on other threads, we would like to consolidate your posts to one thread so that everyone who is interested can follow the progress of your issue. All further activity on this issue will continue on thread linked HERE. Thanks.

Chris W