Fir Filter with high stopband attenuation

Hi ,

I am facing some problem with filter implementation.

Sampling frequency of my ADC %60hz . ADC will give data
which have frequency range from 0-5120hz. Because of hardware limitation I cannot
down sample below 2560hz. But signal of interest is 0-to 5 0hz. So after acquiring
data from adc I am implementing fir filter whose sampling frequency is 10240hz,
and cutoff frequency 50hz. After that I am decimating filtered data by 20
times. I mean to say that actually I am
over sampling the signal 20 times.

Fs= 2560

FcPhz

Decimation factor ;

So effective sampling frequency is = 2560/20= 128hz

My fft spectrum show
frequencies range from 0-64hz.

According my system requirement anything above -80db will be
considered to the signal. In order to achieve this, I should select my filter
stop band attenuation >90db.

But conventional FIR filter cannot give this much attenuation.
Can anyone suggest some technique to achieve this..

Thanks in advance,

Regards,

Ramaraju Start a New Thread

Howdy Willer,

I have a couple of old SHARC boards, one has burned out WR
line. I'd be happy to send that so you can test JTAG on it. It's
probably a 21161 or 21061, but the JTAG is the same.

Patience, persitence, truth,
Dr. mike

On Wed, 29 Apr 2009, Willer Justinvil wrote:

> Mike,
>
> Company purcharsed a HPPCI-ICE afew years ago, and it has not been working working with our target device. I was told by Analog devices that the Target JTAG interface must be the same as described in EE-68 which is TCK must be buffered along with TSM, TDI, and TDO and so forth. I am able to detect the JTAG device with a mountain-ICE and works fine, but with HPPCI it does not work. I was wandering whether anybody would have an evaluation board that would be compatible with the High performance PCI ICE, maybe to purchase or as loaner.
>
> Thanks,
> Willer
>
> --- On Sat, 4/25/09, Mike Rosing wrote:
> From: Mike Rosing
> Subject: [adsp] Re: Fir Filter with high stopband attenuation
> To: "rama raju"
> Cc: a...
> Date: Saturday, April 25, 2009, 10:57 AM
> Howdy Ramaraju,
>
> An FIR can get that good if you have enough taps. So it depends on how
> much delay you can live with. If you need faster response time, then an
> IIR might be a better choice - the trade off is more ripple and non-linear
> phase shifting. If you use a 1000 tap filter you have almost 1/2 second
> delay, but you'll get almost a brick wall filter. What can your system
> response live with?
>
> Patience, persistence, truth,
> Dr. mike
>
> On Sat, 25 Apr 2009, rama raju wrote:
>
>> Hi ,
>
> I am facing some problem with filter implementation.
>
> Sampling frequency of my ADC %60hz . ADC will give data
> which have frequency range from 0-5120hz. Because of hardware limitation I cannot
> down sample below 2560hz. But signal of interest is 0-to 5 0hz. So after acquiring
> data from adc I am implementing fir filter whose sampling frequency is 10240hz,
> and cutoff frequency 50hz. After that I am decimating filtered data by 20
> times. I mean to say that actually I am
> over sampling the signal 20 times.
>
> Fs= 2560
>
> FcPhz
>
> Decimation factor ;
>
> So effective sampling frequency is = 2560/20= 128hz
>
> My fft spectrum show
> frequencies range from 0-64hz.
>
> According my system requirement anything above -80db will be
> considered to the signal. In order to achieve this, I should select my filter
> stop band attenuation >90db.
>
> But conventional FIR filter cannot give this much attenuation.
>
> Can anyone suggest some technique to achieve this..
>
> Thanks in advance,
>
> Regards,
>
> Ramaraju
> Start a New Thread

Mike,

Company purcharsed a HPPCI-ICE afew years ago, and it has not been working working with our target device. I was told by Analog devices that the Target JTAG interface must be the same as described in EE-68 which is TCK must be buffered along with TSM, TDI, and TDO and so forth. I am able to detect the JTAG device with a mountain-ICE and works fine, but with HPPCI it does not work. I was wandering whether anybody would have an evaluation board that would be compatible with the High performance PCI ICE, maybe to purchase or as loaner.

Thanks,
Willer

--- On Sat, 4/25/09, Mike Rosing wrote:
From: Mike Rosing
Subject: [adsp] Re: Fir Filter with high stopband attenuation
To: "rama raju"
Cc: a...
Date: Saturday, April 25, 2009, 10:57 AM

Howdy Ramaraju,

An FIR can get that good if you have enough taps. So it depends on how
much delay you can live with. If you need faster response time, then an
IIR might be a better choice - the trade off is more ripple and non-linear
phase shifting. If you use a 1000 tap filter you have almost 1/2 second
delay, but you'll get almost a brick wall filter. What can your system
response live with?

Patience, persistence, truth,
Dr. mike

On Sat, 25 Apr 2009, rama raju wrote:

>

Hi ,

I am facing some problem with filter implementation.

Sampling frequency of my ADC =2560hz . ADC will give data
which have frequency range from 0-5120hz. Because of hardware limitation I cannot
down sample below 2560hz. But signal of interest is 0-to 5 0hz. So after acquiring
data from adc I am implementing fir filter whose sampling frequency is 10240hz,
and cutoff frequency 50hz. After that I am decimating filtered data by 20
times. I mean to say that actually I am
over sampling the signal 20 times.

Fs= 2560

Fc=50hz

Decimation factor =20;

So effective sampling frequency is = 2560/20= 128hz

My fft spectrum show
frequencies range from 0-64hz.

According my system requirement anything above -80db will be
considered to the signal. In order to achieve this, I should select my filter
stop band attenuation >90db.

But conventional FIR filter cannot give this much attenuation.

Can anyone suggest some technique to achieve this..

Thanks in advance,

Regards,

Ramaraju Start a New Thread