creating 4 different waveforms using equations

[imperial-aero]

Hi,

Sorry if this has been posted previously, but I could not find the solution to my problem. I'm trying to generate 4 different waveforms and output them using a PCI 6229 device. I want to use the following equations to generate these waves.

p1  = p*cos(theta)*exp(i*w*t)

p2 = p*cos(theta+pi/4)*exp(i*w*t)

p3 = p*cos(theta+pi)*exp(i*w*t)

p4 = p*cos(theta+3*pi/4)*exp(i*w*t)

In the above equation p is the amplitude, theta is an angle in radians, w is the frequency, t is the time in seconds, and i =sqrt(-1). The p*exp(i*w*t) are common to all equations which might simply the block diagram. Is there an example on this?

Thank you for any help.

[craigc]

Sounds like Homework to me....

However put the math in a for loop and use Iteration counter multiplied by 1/Fs to give you a value of t (Time).  Then set n to however many data points you want. Use controls for all the other variables so that you can play around with their values.  Then repeat for the other three equations 🙂

Craig

[imperial-aero]

Thanks for the suggestion Craig. I'd like to add that I'm very new to LabVIEW and did not fully understand what you explained.

This particular graph is a part of a larger block diagram. I wanted to generate these four waveforms either using equations or just by playing around with the phases. I've created a VI which mimicks some features I want to have on it, however I've got two issues with this.

Firstly, I don't know how to change the phases so that three of the waves are out of phase by pi/4, pi/2 and pi to the first one.

Secondly, I'm not sure how to use the complex variable (i=sqrt(-1)) in LabVIEW.

Ruf. 

Message Edited by imperial-aero on 02-15-2008 11:20 AM

[craigc]

Hi Imperial

If you put the sine function in a for loop and then wire the [ I ] count (multiplied by say 0.002 )to its input and run it over say 400 times and graph the Output array you will get a sine wave.  So for your needs you just put the math in a for loop and use the Blue I terminal for time.  The Sqrt(-1) is a complex number.  I have not done a great deal with them but i believe there is a complex number representaion which allows a a Real and Imaginary part to it.  Because your exponential part is imaginary you will use say 0R+1.2I for the number.  This means all your calculations should be in complex form, from what i understand.

Please anybody correct me if I am wrong as i have a very limited experience with complex numbers in LabVIEW 🙂

I would have drawn you a pic but its hometime for me:)

craig