[Software and Electronic Applications ]

WinIIr 2.0



WinIIr is a rather specific tool for people who have to design digital "Infinite Impulse Response" filters.

There are several applications available for this purpose, starting with "MATLAB" ©.

Anyway, WinIIr offers certain advantages:

The Main Dialog Box:

Here is a example of the main application screen for an "elliptic" band pass filter of order 8:

The available features are self-explanatory for people accustomed to filter design.

Four types of filters are available, as usual: low pass, high pass, band pass and band stop, with three possible implementations:

Butterworth, Chebyshev and Cauer (Elliptical). For the Chebyshev and Cauer implementations, the maximum ripple must be specified.

For the Cauer filter, specifying the attenuation is also required.

The upper diagram displays the Frequency Response on a linear or logarithmic frequency scale.

The lower diagram displays the Time Response at the selected Marker frequency.

The scale of each abscissa is selected by a small spin control.

 The Code Editor:

An Editor is included to access the filter description in text format. It is accessible through the "View Code" button.

Here is an example of the filter description for a simple "high pass" filter:


Here is the synthesis result accessible through the Editor Window:

WinIIr Filter Designed  :   2 jul. 2020 at 13:13




Type : High Pass, fc = 5000 @ fs = 48000

Kind : Butterworth, Order 4




Biquad section  1 :

Denominator                     Numerator

a0 =  1.0000000000000000e+000,  b0 =  5.7390163562541840e-001

a1 = -1.0155428255941767e+000,  b1 = -1.1478032712508368e+000

a2 =  2.8006371690749693e-001,  b2 =  5.7390163562541840e-001

Biquad section  2 :

Denominator                     Numerator

a0 =  1.0000000000000000e+000,  b0 =  7.2725356179509404e-001

a1 = -1.2869054402745597e+000,  b1 = -1.4545071235901881e+000

a2 =  6.2210880690581649e-001,  b2 =  7.2725356179509404e-001




Analyzing a given filter:

WinIIr  can also be used for analyzing a specific filter.

For this purpose, you must "Load” a text file containing the sampling frequency and the biquad parameters.

Here is an example of such a file for a RIAA filter:

Here is the result of the Analyze:

The process is interactive, you can modify the filter parameters inside the Filter Editor Window and Analyze it again to see the consequences of the modifications.


The documentation is available in PDF format (645KB): WinIIr2.0.pdf


WinIIr Setup "zipped" executable file (1.5MB): WinIIr_2.0_Setup.exe.zip