Mathematica 9 is now available
Student Support Forum
-----
Student Support Forum: 'derivative of amplitude-frequency characteristic' topicStudent Support Forum > General > Archives > "derivative of amplitude-frequency characteristic"

< Previous Comment | Next Comment >Help | Reply To Comment | Reply To Topic
Author Comment/Response
Bill Simpson
02/06/13 8:25pm

In Response To 'Re: Re: derivative of amplitude-frequency chara...'
---------
I apologize for my last message. The text I added to the bottom of my reply to try to explain the problem that I was seeing was badly worded and confusing.

Here is part of your original code, if I have not made any more mistakes:

In[1]:= sys=s/(1000+s);
ampl=Abs[sys/.{s->2*Pi*f*I}];
D[ampl,f]

Out[3]= 2*Pi*(((-2*I)*f*Pi)/(1000 + (2*I)*f*Pi)^2 + (1000 + (2*I)*f*Pi)^(-1))*Abs'[f/(1000 + 2*I)*f*Pi)]

That Out[3] is, I believe, one of the things you want to plot.

Do you get the same result if you do this?

If so then observe the first part of that does not appear to be a Real valued function of f and the second part of that is the derivative of the absolute value function which my Mathematica does not know how to further evaluate.

It is that second part which I tried to (badly) question in my previous message to you.

So I believe the reason you are not seeing anything from your Plot is that you do not have a Real valued function of f. Check each of those to see if you can confirm that for yourself.

If you can confirm that then we need to figure out what needs to be changed to get the unknown Real valued function.

I hope this is a better explanation.

URL: ,

Subject (listing for 'derivative of amplitude-frequency characteristic')
Author Date Posted
derivative of amplitude-frequency characteristic devil 02/05/13 2:19pm
Re: derivative of amplitude-frequency character... Bill Simpson 02/05/13 6:43pm
Re: Re: derivative of amplitude-frequency chara... devil 02/06/13 2:22pm
Re: Re: Re: derivative of amplitude-frequency c... Bill Simpson 02/06/13 8:25pm
Re: Re: Re: Re: derivative of amplitude-frequen... devil 02/07/13 1:08pm
Re: derivative of amplitude-frequency character... devil 02/20/13 07:16am
< Previous Comment | Next Comment >Help | Reply To Comment | Reply To Topic