Filter's type - matlab function

[daniel488]

Hey,

i've line in matlab example code:

LPF = LPF_b*LPF_prev + LPF_a*mixer_I + LPF_a*mixer_I_prev ;

This is part of 'for' loop where is signal 'mixer_I' filtering.
I see this is IIR but I dont know how could I write its transfer function.
This is one of LPF in costas loop. I cant find any theory about designing this kind of filters. Could you help me?

EDIT:
After thinking:smile:

LPF/mixer_I = (LPF_a + LPF_a*z^(-1)) / (1 - LPF_b*z^(-1))

Is it correct?

 

[polytech1989]

that's correct.