Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
Why is the number of decimation FIR filter states different with that

Subject: Why is the number of decimation FIR filter states different with that

From: fl

Date: 9 Apr, 2013 15:40:18

Message: 1 of 2

Hi,
I design a decimation low pass filter (decimation 16). It is an FIR, low pass 16 Hz, stop frequency is 50 Hz, sampling rate is 10000 Hz. I use filterbuidler design this filter. To my surprise, when I click the mfilt.firdecim variable, it shows:


FilterStructure: Direct-Form FIR Polyphase Decimator
Numerator: [1X582 double array]
State: [576X1 double array]
...


How to explain the difference between Numerator and State?

Thanks,

Subject: Why is the number of decimation FIR filter states different with that

From: Navan Ruthramoorthy

Date: 10 Apr, 2013 18:45:08

Message: 2 of 2

Hi,

Polyphase filters are implemented by decomposing the original filter into several smaller filters that run on decimated signal. The number of filters is equal to the decimation factor. For an FIR filter the number of states is equal to (number of coeffecients - 1). So if there are say 6 filters each having 97 coefficients then you have a total of 582 (97*6) coefficients and 576 (96*6) states.

Navan

fl <rxjwg98@gmail.com> wrote in message <fb687bb3-7c7c-45c7-a40d-4d67722fd26d@googlegroups.com>...
> Hi,
> I design a decimation low pass filter (decimation 16). It is an FIR, low pass 16 Hz, stop frequency is 50 Hz, sampling rate is 10000 Hz. I use filterbuidler design this filter. To my surprise, when I click the mfilt.firdecim variable, it shows:
>
>
> FilterStructure: Direct-Form FIR Polyphase Decimator
> Numerator: [1X582 double array]
> State: [576X1 double array]
> ...
>
>
> How to explain the difference between Numerator and State?
>
> Thanks,

Tags for this Thread

No tags are associated with this thread.

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us