Newbie - what does this filter do in DSP?

[monty_mm]

Hello everyone,
i was wondering about the following filter

input x ---> (-1)^n ---> output y

i cannot understand what it is doing. my teacher explained it but i couldnt quite get it from his explanation. can anyone help me?

any explanation or direction on where to read about it is welcome. thanks.

 

[xulfee]

just convert ur all equation to frequency domain n see,wht is going on

 

[monty_mm]

Hi, thanks for your response. i have done that but unfortunately i couldnt make any sense of it (unless i'm going wrong somewhere). I'm new to matlab anyways, and new to DSP as well!!!

if anyone could breifly explain what is does in simple terms, it would be deeply appreciated. thanks.

 

[xulfee]

can u send me code which u've writen in matlab? look at fourier transform of h=(-1)^n,how long is ur n? convolve this with x,u'll get y

 

[monty_mm]

hi,
thanks for your reply,

well i'm actually trying to do this in mathcad. i will try to post what i've done so far and maybe you can tell me what i'm doing is correct. i will post in a few hours

 

[RBB]

The impulse response is specified to be h = (-1)^n
Using the z-transform the transfer function is H(z) = 1/(1+z^-1)
From this we can see we have a zero at the origin and a pole at z=-1.
The frequency response is H(w) = 1/(1+e^(-i*w))
The magnitude reponse: |H(w)| = 1/(2+2*cos(w))^0.5
The phase response: <H(w) = atan(sin(w)/(1+cos(w))).
We can see that since the pole lies on the unit circle the system is unstable.

 

[xulfee]

ya tht wht i want to do,that this impulse responce has pole on unit circle thats y system is unstable

 

[chegu.balaji]

h[n] is a marginally stable to be precise.