FIRDesign2 2.3

Short:        FIR Filter Designer V2.3
Author:       harald.zottmann@t-online.de
Uploader:     harald zottmann t-online de
Type:         misc/sci
Version:      2.3
Replaces:     misc/sci/FIRDesign2*
Architecture: m68k-amigaos



 FIR Filter Designer
 ===================

 The  Amiga FIR  Filter Designer  designs  optimized   Finite  Impulse
 Response  Filters.

 Amiga OS 3.x is required. The program  requires a  minimum  Workbench
 screen size of 640x400.

 The FIR Filters designed  by the  program  FIR  Filter  Designer V2.3
 can be  loaded by  the  program  AudioLab16  from  Maurizio  Ciccione.
 AudioLab16 can be found on  the  Aminet  in the  directory  /mus/edit.

 The problem  of  designing  finite  impulse  response  (FIR)  digital
 filters  experienced  great  activity in  the early  1970`s.  Most of
 this  work was  directed at the  problem  of  optimal  filter  design,
 in the weighted  Chebyshev  sense.  The  algorithm  for  this program,
 by McClellan, Parks and Rabiner, will  design the  optimal  Chebyshev
 approximation for linear phase filters. The   Chebyshev  optimization
 is done very efficiently by means of  the  Remez  exchange  algorithm,
 and this particular  FIR filter design  program  has  found wide  use.

 The window method filter design process is  based upon Fourier series.
 It is possible to represent a frequency  function as a Fourier series,
 whose coefficients represent the coefficients of the filter.

 To form a casual filter, the Fourier series is truncated  and shifted.
 Truncating the Fourier series causes a phenomenon  called  the "Gibbs
 effect" - a spike  occurs  wherever there is a  discontinuity  in the
 desired  magnitude  of the filter. To  counteract  this,  the  filter
 coefficients  are convolved in the frequency domain with the spectrum
 of a window  function, thus  smoothing  the edge  transitions  at any
 discontinuity. This convolution in the frequency domain is equivalent
 to multiplying the filter coefficients  with the window  coefficients
 in the time domain.



 History
 =======

 Date      Version  Type      Comments
 ----      -------  ----      --------
 06/08/98  V2.30    Release   - Automatic refresh for Prism window
                              - Selectable bitwidth for filter taps
                              - Some minor bugfixes

 08/03/98  V2.20    Release   - Updated GUI to fit for larger fonts
                              - Changed registration address

 06/02/98  V2.10    Release   - Fixed a serious bug with big font sizes
                              - New ToolType for FONTNAME and FONTSIZE

 20/01/98  V2.00    Release   - Window method filter design
                              - Requires OS3.x now
                              - Improved GUI
                              - Progress bar
                              - Extended documentation
                              - Recompiled with SAS/C V6.58

 20/07/96  V1.20    Release   - ToolType support
                              - Filterlength now up to 512 taps
                              - Internal improvements
                              - Displays floating point errors
                              - View log file with external viewer
                              - Displays also the corrected phase

 01/05/96  V1.10    Release   - Versions for: MC 68000
                                              MC 68020
                                              MC 68040
                              - Updated the installer script
                              - Now compatible with AudioLab16
                              - Grids in the Prism window
                              - Some redesigns and optimizations
                              - Fixed Bug with too small workbench

 29/11/95  V1.01    Release   - Fixed several Enforcer Hits
                              - Fixed Bug with not updating gadgets
                              - Recompiled with SAS/C V6.56
                              - Less Shareware Requesters
                              - Installer Script
                              - Added Pattern in Filerequester
                              - More Examples

 21/07/95  V1.00    Release   First AMINET Release