Reply by January 29, 20102010-01-29
[b,a] = butter(10,0.5,'high')

and then

freqz(b,a,1000,4000)

what is the passband of your filter?
you want to reject dc and some lower freqs, but where is the signal content?

yours,

Raj

--- In m..., kn srivastava wrote:
>
> On Fri, Jan 15, 2010 at 03:07, yousef qoqazeh wrote:
>
> > try this:
> > N = 4; %Constant
> > x = x(1:N:end,:);%x is your signal
> > sample_rate = sample_rate* N;
> >
> > or you can use upsample command in matlab
> I tried upsample command in Matlab but the upsampled filter is not good. I
> will have to redesign the filter. The specifications are as follows:
>
> It should be a digital filter (IIR) with sampling frequency of 4000 Hz and
> doing the following:
>
> 1) Doesn't pass dc i.e. 0 Hz,
> 2) Also doesn't pass 50, 100 and 150 Hz
>
> How can I do it?
>
> Kailash
>
Reply by January 19, 20102010-01-19
On Fri, Jan 15, 2010 at 03:07, yousef qoqazeh wrote:

> try this:
> N = 4; %Constant
> x = x(1:N:end,:);%x is your signal
> sample_rate = sample_rate* N;
>
> or you can use upsample command in matlab
I tried upsample command in Matlab but the upsampled filter is not good. I
will have to redesign the filter. The specifications are as follows:

It should be a digital filter (IIR) with sampling frequency of 4000 Hz and
doing the following:

1) Doesn't pass dc i.e. 0 Hz,
2) Also doesn't pass 50, 100 and 150 Hz

How can I do it?

Kailash
Reply by January 14, 20102010-01-14
Hi,

I just have *a* and *b* coefficients. It would really help if you suggest a
reference.

Regards
Kailash

On Thu, Jan 14, 2010 at 20:37, Mreza rahimi wrote:

> hi
> you should just change ws and wp.
> ws and wp are related to sampling frequency.
> you can find the relation between these in MATLAB help.
> Regards
>
> On 1/14/10, kn srivastava wrote:
>>
>> I have a digital filter that is designed for 1kHz sampling frequency.
>> Everything else remaining the same, I want that filter to work for 4 kHz
>> sampling frequency.
>>
>> What do I need to do?
>>
>> I am not a filter guy and my background is power system. That is why I am
>> asking you here this basic question.
>>
>> Kailash
>
Reply by January 14, 20102010-01-14
I have a digital filter that is designed for 1kHz sampling frequency.
Everything else remaining the same, I want that filter to work for 4 kHz
sampling frequency.

What do I need to do?

I am not a filter guy and my background is power system. That is why I am
asking you here this basic question.

Kailash