Scicos Block
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Generic Finite Impulse Response filter block

Contents

• Generic Finite Impulse Response filter block
  • Palette
  • Description
  • Basic blocks equivalent model
  • Dialog box
  • Default properties
  • Interfacing function
  • Computational function
  • Authors
  • Bibliography

Palette

• Filter - Digital filters palette

Description

Finite impulse response filters are defined with the discrete state equation :

$$\begin{eqnarray} y\left(k\right)=\sum^{N-1}_{i=0}a_{i}x\left(k-i\right) \end{eqnarray}$$

In the Z transform domain, this equation is able to be rewritten by :

$$\begin{eqnarray} H\left(Z\right)=\sum^{N-1}_{i=0}a_{i}Z^{-i} \end{eqnarray}$$

where $a_{i}$ are the values of the coefficients of the impulse response, N is the number of coefficients and $Z^{-1}$ the delay operator.

An example of a finite impulse response filter with 4 coefficients build with scicos basic blocks is shown in the following section.

Basic blocks equivalent model

Dialog box

• Type of FIR
  Type 'vec' of size 1. integer. Set the type of the impulse response

  If set 1

  
  • Number of coefficients
    number of coefficients
    Properties : Type vec of size -1.

  • Vector of impulse response
    impulse response
    Properties : Type vec of size -1.

  • Size of input vectors
    size of the regular input
    Properties : Type vec of size -1.

  • Plot impulse response (0:No/Windows Id)?
    plot impulse response in a graphic window
    Properties : Type vec of size 1.

  If set 2

  
  • Size of the filter
    filter order
    Properties : Type vec of size 1.

  • Sampling frequency
    set the sampling period to compute the impulse response
    Properties : Type vec of size 1.

  • Type of wfir filter (lp,hp,bp,sb)
    filter defintion
    Properties : Type str of size 1.

  • Low - High frequency cutoff
    2-vector of cutoff
    Properties : Type vec of size 2.

  • Type of filtering window (re,tr,hn,hm,kr,ch)
    filtering window
    Properties : Type str of size 1.

  • Chebychev or Kaiser window parameters:
    Chebychev or Kaiser windw parameters
    Properties : Type vec of size 2.

  • Plot impulse response (0:No/Windows Id)?
    plot impulse response in a graphic window
    Properties : Type vec of size 1.

  If set 3

  
  • Size of the filter
    number of coefficients
    Properties : Type vec of size -1.

  • Size of input vectors
    size of the regular input
    Properties : Type vec of size -1.

  • Frequency Sampling
    set the sampling period to compute the impulse response
    Properties : Type vec of size -1.

  • Roll-Off Factor
    filter parameter
    Properties : Type vec of size -1.

  • Output Gain
    the output gain of the filter
    Properties : Type vec of size -1.

  • Plot impulse response (0:No/Windows Id)?
    plot impulse response in a graphic window
    Properties : Type vec of size 1.

  If set 4

  
  • Size of the filter
    number of coefficients
    Properties : Type vec of size -1.

  • Size of input vectors
    size of the regular input
    Properties : Type vec of size -1.

  • Frequency Sampling
    set the sampling period to compute the impulse response
    Properties : Type vec of size -1.

  • Roll-Off Factor
    filter parameter
    Properties : Type vec of size -1.

  • Output Gain
    the output gain of the filter
    Properties : Type vec of size -1.

  • Plot impulse response (0:No/Windows Id)?
    plot impulse response in a graphic window
    Properties : Type vec of size 1.

  If set 5

  
  • Size of the filter
    number of coefficients
    Properties : Type vec of size -1.

  • Size of input vectors
    size of the regular input
    Properties : Type vec of size -1.

  • Frequency Sampling
    set the sampling period to compute the impulse response
    Properties : Type vec of size -1.

  • BT Factor
    filter parameter
    Properties : Type vec of size -1.

  • Output Gain
    the output gain of the filter
    Properties : Type vec of size -1.

  • Plot impulse response (0:No/Windows Id)?
    plot impulse response in a graphic window
    Properties : Type vec of size 1.

• Inherit (no:0, yes:1)
  Type 'vec' of size 1. Herits events by its regular input ports (disable the event input port).

Default properties

• always active: no
• direct-feedthrough: yes
• zero-crossing: no
• mode: no
• regular inputs:
  - port 1 : size [1,1] / type 1
  
• regular outputs:
  - port 1 : size [1,1] / type 1
  
• number/sizes of activation inputs: 1
• number/sizes of activation outputs: 0
• continuous-time state: no
• discrete-time state: yes
• object discrete-time state: no
• name of computational function: nfilter

Interfacing function

• MODNUMCOS/macros/scicos_blocks/Filter/RIFGEN_f.sci [view code]

Computational function

• MODNUMCOS/routines/filter/nfilter.c (Type 4) [view code]

Authors

A. Layec

Bibliography

LARY_CR: Software package for the Analysis of Cardio Vascular and Respiratory Rhythms, in the SCILAB_SCICOS environment. Available : http://www.inria.fr/rrrt/rt-0259.html