FOREWORD by Dr. John O'Donnell
As I became more experienced with implementing digital filters on various DSP chips I needed to develop digital filters with special characteristics. DISPRO could be used to design FIR filters with arbitrary magnitude characteristics, but IIR filters with arbitrary characteristics required the use of numerical optimization methods which often did not yield useful results, and usually were not interactive. Over a period of a few years I developed a software package, STOZXFR, in Visual Basic, that provided real-time user interaction and graphical output, allowing the user to manipulate the poles and zeros of an IIR filter in order to achieve a desired magnitude or delay characteristic in the frequency domain.
I've successfully tackled many projects using DISPRO and STOZXFR, and hope that any one who downloads these design tools will have similar results, and will also learn much about digital filter design and behavior.
What is DISPRO?
DISPRO is a professional-level software package for designing digital filters, and for evaluating the performance of the digital filter when it is implemented with the actual arithmetic characteristics of the target DSP processor.
DISPRO was the first commercially available digital filter design package for the IBM PC, having been introduced in 1983. It was marketed around the world by Signix Corporation, and is now being offered as freeware by its creator, Dr. John O'Donnell.
Considering its origins, DISPRO was, and remains, a DOS executable. It will, however, run in a DOS or Command Prompt window under Microsoft Windows® XP, and in Vista and Windows 7 using DOSBox (see discussion on the Win7 Operation page).
DISPRO is an extremely useful software package, and it has significant educational value. There is no economic incentive to convert it to a Windows application, so it is being offered to the DSP fraternity in its original DOS implementation. It is hoped that as freeware DISPRO will survive its author and be of value as long as future versions of Windows will allow DOS applications to run.
In addition to the "standard" designs — Butterworth, Chebyshev, Elliptic (or Cauer/Foster), and Parks-McClellan-Remez — DISPRO provides special implementation features.
Complete details are found at DISPRO Features.
What is STOZXFR?
STOZXFR provides two capabilities: (i) interactive adjustment of a z-domain transfer function to achieve a desired magnitude or delay characteristic, and (ii) conversion of an arbitrary s-domain transfer function to a z-domain equivalent which can be adjusted to optimize the match between s- and z-domain characteristics. It is a Windows® application optimized for a 1024x768 display. More details are at StoZ Background, and a detailed operations guide is at StoZ User Guide.
This Web site last updated 5 July 2012[Digital Logic Design - THE resource for Digital Logic Design! ]
[This is the personal web site of Dr. John O'Donnell]