Modeling Filters described in frequency domain in Simulink and /or Matlab

Hi,

I have a signal f(x), and two filters H(w) and G(w) where H(w) = e^(jw/2)*cos(w/2) and G(w) = 4*e^(jw/2)*sin(w/2)

The output is G(w)H(w)F(w).

I have the signal f(x) as a vector. How do I simulate this system in Matlab or Simulink.

thanks

Answer 1

[Wayne King]

In your particular example, that is easy:

Your first filter:

 H(w) = e^(jw/2)*cos(w/2)

is h(n) = \delta(n+1) + \delta(n)

Note that above is noncausal, so you can use the causal version

h = [1 1];

Your second filter:

G(w) = 4*e^(jw/2)*sin(w/2)

is

g(n) = 2\delta(n+1)+2\delta(n)

also, noncausal, you can use

g = [2 2];

You can get the resulting FIR filter with

b = conv(h,g);

In general, if you want to design filters in the frequency domain using magnitude only, you can use:

fir2 or fdesign.arbmag

If you want to design with phase and magnitude, you can use:

fdesign.arbmagnphase in the DSP System Toolbox.

[Ashraf]

Thanks. And what if I have H(w) and G(w) as e^(j*w )*(cos(w ))^3 and 4 * e^(j*w )*(sin(w)) respectively? I have many filters where w is being multiplied by two in each.

How did you come up with this conversion to [1 1] and [2 2] .. I need to learn and do by myself

thanks again!

[Wayne King]

For that I just found the inverse Fourier transform with a pencil and paper.

For your other transfer functions, did you get my response about fdesign.arbmagnphase?

Something like:

   F = linspace(0,1,100);
   H = exp(1i*F ).*(cos(F)).^3;
   d = fdesign.arbmagnphase('N,F,H',50,F,H);
   Hd = design(d);