ScopeIIR ScreenshotScopeIIR™ is the premiere software tool for Infinite Impulse Response (IIR) filter design.


ScopeIIR provides a comprehensive IIR filter design capability.  It instantly designs high-order IIR filters based on the Butterworth, Chebyshev, or Elliptic analog prototypes.  It can design lowpass, highpass, bandpass, and bandstop filters, with frequency and gain characteristics you specify.


ScopeIIR provides a sophisticated set of plots and displays that let you fully analyze the characteristics of your filter design, including:

  • Frequency Response Plots
    • Magnitude
    • Phase
    • Unwrapped phase
    • Group delay
    • Phase delay
  • Time Response Plots
    • Impulse response
    • Step response
    • Combined impulse and step response
  • Data Displays
    • Biquad coefficients
    • Direct Form coefficients
    • Poles and zeros
    • Design specifications
    • Impulse response
    • Step response
  • Pole-Zero Plot

The Pole-Zero Plot allows you to directly alter the locations of your filter’s poles and zeros, so you can make fine adjustments to the characteristics of the filter that has been designed from your specifications.

All plots feature a sophisticated multi-level zoom capability that allows you to quickly examine any area of the plot in fine detail.

All displays are presented in a six-pane layout, with selectable views for each pane so you can organize the plots and data display to match your preference and make best use of available screen space.


ScopeIIR provides a comprehensive set of data file outputs to allow you to easily implement your filter in your system:

  • Biquad Coefficients – Poles and zeros are automatically grouped together into optimal biquads, for an easy, accurate, and stable implementation
  • Direct Form Coefficients
  • Poles and Zeros
  • Design Specifications
  • Impulse Response
  • Step Response

Each data output can be in any of the following file formats:

  • Plain text
  • C
  • C++
  • Matlab

Each of the above formats can be tailored to allow you to generate files that are compatible with your preferred coding style.


The ScopeIIR distribution file includes:

  • A comprehensive set of IIR filter design example projects
  • Example IIR filter implementations in C and C++, including project files for Microsoft Visual Studio. Implementing your own IIR filter is as easy as modifying the example ScopeIIR filter design project to meet your specifications, exporting the IIR filter data files from ScopeIIR, and recompiling in Visual Studio!