design filter from freq. response

hi everybody,
I don't know much about Matlab. I have just started working on matlab. Now I want to design a filter using remez algorithm. I have my own freq. response;
specified freq. response is not standard lowpass, highpass, bandpass or bandstop. Basically it is lowpass but its band pass region is a parabolic curve. So I was taking inverse fft of the freq spectre and then I was applying window on it. But in matlab even inverse fft is not giving me correct results.
Can anybody suggest me the way to design the filter ?
Thanks Start a New Thread

Use the invfreqz command...here is a snippet from its help. I think it will
do what you want.

Nandan
[B,A] = INVFREQZ(H,W,NB,NA) gives real numerator and denominator
coefficients B and A of orders NB and NA respectively, where
H is the desired complex frequency response of the system at frequency
points W, and W contains the normalized frequency values within the
interval [0, Pi] (W is in units of radians/sample).

On 4/28/06, s...@qualcorelogic.com wrote:
>
> hi everybody,
> I don't know much about Matlab. I have just started working on matlab. Now
> I want to design a filter using remez algorithm. I have my own freq.
> response;
> specified freq. response is not standard lowpass, highpass, bandpass or
> bandstop. Basically it is lowpass but its band pass region is a parabolic
> curve. So I was taking inverse fft of the freq spectre and then I was
> applying window on it. But in matlab even inverse fft is not giving me
> correct results.
> Can anybody suggest me the way to design the filter ?
> Thanks
> Start a New Thread

Hi all,
I need a help in ploting the OFDM Spectral shape using matlab, so that I can always visualize the adjacent channel interference. Any idea or matlab codes would be of great help.
Rgds,
Jasan Start a New Thread