# Resampling Polyphase Fir Filter

Started by October 23, 2015
```hello,
i am trying to do 12 to 1 downsampling and 1 to 12 upsampling with
polyphase fir filter, I wanted to know how to design the inner filter.
suppose passband frquency is 0.5, stopband freq is 0.75. input sample rate
is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is 12
path filter with filter length is equal to 348 .each path is followed by
29 taps.how to design the inner filter such that it meets the
specification of the synthesis filter..

---------------------------------------
Posted through http://www.DSPRelated.com
```
```On 23.10.15 14:13, angeleye wrote:
> hello,
> i am trying to do 12 to 1 downsampling and 1 to 12 upsampling with
> polyphase fir filter, I wanted to know how to design the inner filter.
> suppose passband frquency is 0.5, stopband freq is 0.75. input sample rate
> is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is 12
> path filter with filter length is equal to 348 .each path is followed by
> 29 taps.how to design the inner filter such that it meets the
> specification of the synthesis filter..
>

Homework / study project?

--

-TV

```
```>hello,

>suppose passband frquency is 0.5, stopband freq is 0.75. input sample
rate
>is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is 12
>path filter with filter length is equal to 348 .each path is followed by
>29 taps.how to design the inner filter such that it meets the
>specification of the synthesis filter..
>

why suppose a harsh requirement? 0.1/24 & 0.75/24 upsampled by 12 means
0.1/(24*12) & 0.75/(24*12) = 0.0017 & 0.0026 ratio

Too narrow and too sharp.

Kaz

---------------------------------------
Posted through http://www.DSPRelated.com
```
```>>hello,
>
>>suppose passband frquency is 0.5, stopband freq is 0.75. input sample
>rate
>>is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is
12
>>path filter with filter length is equal to 348 .each path is followed
by
>>29 taps.how to design the inner filter such that it meets the
>>specification of the synthesis filter..
>>
>
>why suppose a harsh requirement? 0.1/24 & 0.75/24 upsampled by 12 means
>0.1/(24*12) & 0.75/(24*12) = 0.0017 & 0.0026 ratio
>
>Too narrow and too sharp.
>
>Kaz
>
>---------------------------------------
>Posted through http://www.DSPRelated.com

how to find the 2 sided bandwidth  stopband frequency and the sampling
rate AND weigth of the inner filter from the given analysis filter.
for example, the input sample rate is 24 .if we do 12 to 1 downsampling
and then upsampling of 1 to 12 .the output sample rate will become 24/12 =
2. but how do we find the transition band.i tried using sampling theorem.
nyquist rate =2sided band + transition bandwidth. Asuming the 2 sided
banwidth same as the analysis filter and nyquist rate equal to 2. Is it
the right way to do it.
---------------------------------------
Posted through http://www.DSPRelated.com
```
```>On 23.10.15 14:13, angeleye wrote:
>> hello,
>> i am trying to do 12 to 1 downsampling and 1 to 12 upsampling with
>> polyphase fir filter, I wanted to know how to design the inner filter.
>> suppose passband frquency is 0.5, stopband freq is 0.75. input sample
>rate
>> is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is
12
>> path filter with filter length is equal to 348 .each path is followed
by
>> 29 taps.how to design the inner filter such that it meets the
>> specification of the synthesis filter..
>>
>
>
>Homework / study project?
>
>--
>
>-TV
study project
---------------------------------------
Posted through http://www.DSPRelated.com
```
```>>
>>---------------------------------------
>>Posted through http://www.DSPRelated.com
>
>how to find the 2 sided bandwidth  stopband frequency and the sampling
>rate AND weigth of the inner filter from the given analysis filter.
>for example, the input sample rate is 24 .if we do 12 to 1 downsampling
>and then upsampling of 1 to 12 .the output sample rate will become 24/12
2. but how do we find the transition band.i tried using sampling theorem.
>nyquist rate =2sided band + transition bandwidth. Asuming the 2 sided
>banwidth same as the analysis filter and nyquist rate equal to 2. Is it
>the right way to do it.
>---------------------------------------
>Posted through http://www.DSPRelated.com

upsample by 12 then downsample by 12. Why? what do do in between?

Kaz
---------------------------------------
Posted through http://www.DSPRelated.com
```
```On 2015-10-23 13:13, angeleye wrote:
> hello,
> i am trying to do 12 to 1 downsampling and 1 to 12 upsampling with
> polyphase fir filter, I wanted to know how to design the inner filter.
> suppose passband frquency is 0.5, stopband freq is 0.75. input sample rate
> is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is 12
> path filter with filter length is equal to 348 .each path is followed by
> 29 taps.how to design the inner filter such that it meets the
> specification of the synthesis filter..

Why polyphase for integer up/down sampling?

Or I'm missing something?

bye,

--

piergiorgio
```
```>On 2015-10-23 13:13, angeleye wrote:
>> hello,
>> i am trying to do 12 to 1 downsampling and 1 to 12 upsampling with
>> polyphase fir filter, I wanted to know how to design the inner filter.
>> suppose passband frquency is 0.5, stopband freq is 0.75. input sample
>rate
>> is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is
12
>> path filter with filter length is equal to 348 .each path is followed
by
>> 29 taps.how to design the inner filter such that it meets the
>> specification of the synthesis filter..
>
>Why polyphase for integer up/down sampling?
>
>Or I'm missing something?
>
>bye,
>
>--
>
>piergiorgio

Down Sample to Reduce Sample Rate in Proportion to Bandwidth Reduction
and Up Sample to Preserve Input Sample Rate..it is followed by three
filter...
Analysis filter, inner filter and Synthesis Filter,.
my question is how do we find the specification of the inner filter

---------------------------------------
Posted through http://www.DSPRelated.com
```
```On 2015-10-23 21:24, angeleye wrote:
[...]
> Down Sample to Reduce Sample Rate in Proportion to Bandwidth Reduction

You wrote "12 to 1 downsampling".
This does not need polyphase filter.
The upsampling 1 to 12 does not need either.

Other, I do not know... :-)

bye,

--

piergiorgio
```
```On 23.10.15 22:37, Piergiorgio Sartor wrote:
> On 2015-10-23 21:24, angeleye wrote:
> [...]
>> Down Sample to Reduce Sample Rate in Proportion to Bandwidth Reduction
>
> You wrote "12 to 1 downsampling".
> This does not need polyphase filter.
> The upsampling 1 to 12 does not need either.
>
> Other, I do not know... :-)
>
> bye,

It seems to me that his professor has some solution in his mind,
and attempting to fish it out using a weirdly set up problem.

--

-TV

```