PoZeTools version 0.56, december 24, 2019 © 2002 - 2019 - Pieter Suurmond

PoZeTools is free software for digital filter design.
Given a set of poles and zeros, it plots the frequency response, calculates filter coefficients, plots the impulse response and prints the linear difference equation.
The software is written in ISO/ANSI C. Sourcecode and documentation may be downloaded, used and copied for free. It should compile and run well on Linux, BSD, Mac OSX, IRIX, etc. The commandline tool should even still work on Mac OS7-9.
PoZeTools comes with 2 different user interfaces:

1. Commandline tool  PZT
2. CGI webinterface  nph-PZT.cgi

Both programs offer the same functionality and use exactly the same input syntax (poze.ebnf).

PZT

Console application PZT requires no input paramers. Instead, it tries to read-in a textfile named x.poze, in the current directory, containing a number of pole- and zero-locations and an optional gain. When it succeeds, it generates 4 JPEG files, also in the current directory.
So first edit or create input-file x.poze and then run the commandline executable by typing:

        ./PZT

In the first image generated, the given poles and zeros are plotted in the complex z-plane, it may look something like this:



In the second image, the transfer function is drawn, on a linear frequency scale. It contains magnitude-, angle-, and a time-delay-plots. Here 's an example:



The third image shows an overview, containing the complex z-plane and the transfer function on a logarithmic frequency scale. It may look something like this:



The fourth image displays the conversion to the time domain: filter coefficients are calculated and the impulse response is plotted:

   a(0) = 0.037643100555    b(0) =  1.000000000000
   a(1) = 0.101302601065    b(1) = -0.833870873723
   a(2) = 0.179943012472    b(2) =  0.711395491187
   a(3) = 0.212529635999
   a(4) = 0.180502995174
   a(5) = 0.105815572045
   a(6) = 0.037145890166
 
   Difference equation:
 
    y[n] -0.83 y[n-1] + 0.71 y[n-2] = 0.04 x[n] + 0.1 x[n-1] + 0.18 x[n-2]
                                    + 0.21 x[n-3] + 0.18 x[n-4]
                                    + 0.11 x[n-5] + 0.04 x[n-6]

nph-PZT.cgi

CGI application nph-PZT.cgi generates HTML-forms in which the webclient can fill in her poles, zeros and gain, using exactly the same poze syntax as the console application. The web application displays two JPEG images: one for the frequency domain (nph-freq.cgi.jpg) and one for the time domain (nph-time.cgi.jpg). It furthermore shows the filter coefficients and the difference equation (with downrounded coefficients).
So, whereas the console application reads-in a textfile with pole-zero locations and outputs 3 image files, the CGI application reads the pole-zero locations from a web client and returns 2 images.

The CGI application runs on server ecomaan.nl: Here you can design your own LTI filters for free: https://ecomaan.nl/cgi-bin/pzt/nph-PZT.cgi

To install your own CGI service, type "make cgi" and copy the 3 resulting executables cgi/nph-PZT.cgi, cgi/nph-freq.cgi.jpg and cgi/nph-time.cgi.jpg to a new subdirectory in your public_html/cgi-bin. When nph-PZT.cgi is accessed for the first time, it will create the necessary datafiles automatically. Make sure the CGI application is able to create and remove files in its' own directory.

Source code

The latest version of PoZeTools may be found under https://ecomaan.nl/c/.

			PoZeTools0.56.tar.gz	358 kilobytes	Complete sources and documentation, version 0.56, tarred and gzipped.
	After downloading, one may unpack on the commandline by for example: gunzip PoZeTools0.56.tar.gz tar xf PoZeTools0.56.tar gzip PoZeTools0.56.tar cd PoZeTools0.56 ls -als After unpacking, directory PoZeTools0.56 should look something like this:
			cgi/	subdirectory	PoZeTools CGI interface. A webinterface that possibly enables any websurfer to do the same things as with the console application. Tested on the Apache webserver.
			gt/	subdirectory	Minimal graphic toolkit for drawing and writing (not reading) JPG-files. Incorporates the compression-part of the JPEG-library from the Independent JPEG Group (version 6b, 27-Mar-1998). Also include source gt/gt.c in your compiler project.
			Makefile	4 579 bytes	Helpfull to compile PoZeTools and under UNIX. Users with a graphical compiler (IDE) may simply drop all the .c files mentioned here in a standard C project. Also link against the math library.
			poze.ebnf	5155 bytes	Formal description of the input syntax.
			PZT.c	5 5527 bytes	Contains main() for the console application.
			PZT.h	35 bytes	Headerfile containing the version number used for all applications.
			PZT_coeff.h	3 3581 bytes	API headerfile specifying how to manage COEFF objects.
			PZT_coeff.c	15 984 bytes	Implements the creation and destruction of COEFF objects, reading and writing of COEFF data as text(files), computation of COEFF objects out of POZE objects.
			PZT_coeff_graph.h	2 075 bytes	API headerfile specifying COEFF drawing functions.
			PZT_coeff_graph.c	14 169 bytes	Implements impulse response plotter.
			PZT_complex_math.h	4 051 bytes	API headerfile for complex arithmetic in C.
			PZT_complex_math.c	3 489 bytes	Implements complex arithmetic.
			PZT_complex_text.h	4 051 bytes	API headerfile for parsing and writing text.
			PZT_complex_text.c	11 484 bytes	Implements reading and writing of complex numbers (in both polar and rectangular form) from and to strings, files, and the console (stdout).
			PZT_graph.h	2 559 bytes	Headerfile.
			PZT_graph.c	6 528 bytes	Common drawing functions.
			PZT_poze.h	7 188 bytes	API headerfile specifying how to manage POZE objects.
			PZT_poze.c	18 832 bytes	Implementation that reads and writes sets of poles and zeros (and a gain parameter).
			PZT_poze_graph.h	3 160 bytes	API headerfile specifying POZE drawing functions.
			PZT_poze_graph.c	35 202 bytes	Implements plotting of z-planes and frequency responses.
			html	subdirectory	Subdirectory containing this very HTML documentation.
			x.poze	1 046 bytes	Example input file.
	To compile both the commandline-tool and the CGI-interface, type: make all To compile only the commandline-tool, type: make

License

Besides the PoZeTools license, which is printed below, there may be other licenses of interest within this software package (see subdirectory gt).

Thanks