Wasn't sure where to put this - Lowpass Filter in Excel

[BiGyElLoWhAt]

Wasn't sure where to put this -- Lowpass Filter in Excel

Ok I need some excel help, I need to model a sawtooth wave mathematically (done) and then I need to put it through a lowpass filter, but I need to do it in excel. My prof expects an excel spreadsheet, and I have no clue how to put it in there. On wolfram I use plot Ʃ[sin(2*n*pi)/(n*pi)] and that works when I take it out 100 or so terms, but excel doesn't like those kinds of functions.

How can I put it in there?

 

[ModusPwnd]

You are summing over n right? In excel I would just make one column "n" and number it from 1 to 100 or so. Then the column next too it would be sin(2*n*pi)/(n*p)+"previous cell". Here "n" would be a reference to the cell in the adjacent column and "previous cell" would be the cell above which has the rest of the terms of the sum. Does that seem right?

 

[BiGyElLoWhAt]

That seems somewhat right, but I need an x in there. It's actually sum sin(2npix)/npi

 

[cpscdave]

When I was learning Fourier Series, what I would occasionally do to verify my answers was to plot the first N series and see if it looked like what I started with.

To accomplish this what I did is along the first Collum I had 1->N
Then along the first row I put -k->k (the period of the function)
Then just filled in the function information

for you it'd look something like =sin(2*$A1*pi()*A$1)/(2*$A1*pi()))

The $A1 being your N term and the A$1 being your x term, set so as you pull the formula they stay in the right column/row.

Then in row N+1 you sum the collum and plot that

Hope that makes sense :D

 

[rude man]

You haven't specified your lowpass transfer function.

So let's assume it's a 1st order lowpass: 1/(Ts+1) where 1/T = corner radian frequency.

I would write an equivalent finite-difference equation for this function, then pass your triangular wave thru it and get the output. The output can then be plotted by excel's plotting facility.

You need to specify T and you also need to specify the frequency of your triangular input.