FilterDesignLab-IIR

FilterDesignLab-IIR is a design and simulation environment for digital Infinite Impulse Response (IIR) filters. It is structured into four views for designing the gain, analyzing the phase, simulating test signals, and generating code and filter coefficients. For a given filter brickwall specification of a digital lowpass, highpass, bandpass, or bandstop, it instantaneously finds the optimal Butterworth, Cheby-I, Cheby-II, or Elliptical filter of lowest order. The phase shift, the group delay and phase delay and the location of the poles and zeros of the transfer function are displayed along with the filter gain. The design and simulation occurs in real-time and is done either by mouse or text input. The resulting digital filter is instantaneously applied to a test-signal or an imported data set (csv, ascii, txt - format). The test signal resembles either a shifted noisy sine wave, or a step, respectively, delta impulse signal. The raw and the filtered signal are displayed either in the time or in the frequency domain (i.e spectral analysis). The resulting filter algorithm can be realized in a normal form or a second order structure in the direct form 1 or direct form 2. The numerical stability of the resulting algorithm is calculated for a DOUBLE-precision implementation. The filter function can be generated for signal postprocessing or for real time applications, where new data is entering the system at a given rate. The resulting filter coefficients of the corresponding recursive time domain algorithm are available for further use and accessible by Copy&Paste. Alternatively, the code of a double precision Matlab®-Function, or C-function is provided and can be exported into a file. The user can save individual filter designs. The different plots can be exported into PDFs. Each plot features zoom functionality to visually focus on relevant areas and allow for precision editing.