Ideal low pass filter - Simulink

Question

I have the following time-continuous system: input signal -->abs block (in the time domain)-->ideal low pass filter block (in the frequency domain)-->output signal. In simulink I make the abs block with the Fcn block. My problem is to get ideal low pass filter with a 3000Hz band and 1 amplitude (linear scale). How could I get it? Maybe I should use Lowpass filter block? In this case what are the right parameters?

Thank you for your time.

Answer 1

An ideal low-pass filter can be represented as (from https://en.wikipedia.org/wiki/Low-pass_filter):

So I suggest you use the Transfer Fcn block:

If your amplitude/gain is 1, and your cut-off frequency is 3kHz, then the gain K is 1 and the time constant is:

f = 3000;
tau = 1 / (2*pi*f);

and your transfer function is:

num = 1;
den = [tau 1];

Simple!