What decides Number of Taps of FIR filter in Adaptive applications?

Hello,

    If I am designing an adaptive filter to remove
    narrowband interference from wideband signal,
    how can I decide on the order of the FIR filter?

Regards
Bharat
    

On 20 Mar, 07:46, "bharat pathak" <bharat@n_o_s_p_a_m.arithos.com>
wrote:
> Hello,
>
> &#4294967295; &#4294967295; If I am designing an adaptive filter to remove
> &#4294967295; &#4294967295; narrowband interference from wideband signal,
> &#4294967295; &#4294967295; how can I decide on the order of the FIR filter?

Decide on a worst-case scenario for the interference:
Narrowest bandwidth, narrowest transition bands. Use the
standard FIR analysys to estimate the number of coefficients.

Rune

bharat pathak wrote:
> Hello,
> 
>     If I am designing an adaptive filter to remove
>     narrowband interference from wideband signal,
>     how can I decide on the order of the FIR filter?
> 
> Regards
> Bharat
>     

The order of the FIR filter will be approximately this:

1) Determine the narrowest transition band width.  As you go through 
this, you will see that you want to specify the *widest* transitions 
that you can stand - to get the shortest filters.

2) The resulting temporal length of the filter must be at least the 
reciprocal of the narrowest transition band width.

3) The length of the filter in terms of coefficients will be the 
temporal length divided by the sample interval.

Note:  It doesn't matter how many notches there will be - only the one 
single narrowest transition.

Example:

Given: Sample rate = 10kHz.  Sample interval = 1/10^4 = 0.1 msec.

Given: Narrowest transition band width = 10Hz.  (As in needing a notch 
filter at 3,000 Hz that is 10Hz wide and 10Hz transition band on each 
side of the notch for a total bandwidth of just under 30Hz).

Therefore, temporal length of the filter is not less than 1/10Hz = 0.1 
second.

0.1 second filter length / 10^-4 seconds per sample = 1,000 samples 
filter length.

This may be off by a factor of 2 but I hope you get the idea.... From 
here you can check it out.

Fred

bharat pathak wrote:
> Hello,
> 
>     If I am designing an adaptive filter to remove
>     narrowband interference from wideband signal,
>     how can I decide on the order of the FIR filter?

To make a notch at a frequency, you need three taps. Sometimes it can be 
done by two taps.

Whatever is the question posed, so is the answer answered.

VLV

Thanks Fred,

Regards
Bharat