Cascaded Integrator-Comb (CIC) filters (sometimes called "Hogenauer" filters) are a special class of filters described by Eugene B. Hogenauer in his classic paper An Economical Class of Digital Filters for Decimation and Interpolation*.  CIC filters are typically used in hardware (integrated circuit) implementations of FIR decimators and interpolators.

The CIC Editor is shown below:

ScopeFIR lets you analyze CIC filters by generating an impulse response identical to that of a CIC filter with the given parameters.  You specify the:

• Number of stages (N) - The number of cascaded integrator-comb stages in the filter.
• Rate Change Factor (R) - The ratio of input and output sampling frequency.  For example, a CIC which has an input sampling frequency of 100 MHz and an output sampling frequency of 10 MHz has an R of 10.
• Differential Delay (M) - The number of delay elements in the comb sections, usually just 1 or 2.

To use the CIC Editor:

1. Hit the Sampling Frequency button and specify the sampling frequency.
2. Enter the CIC design parameters, N, R, and M.
3. Hit the Design button to generate the CIC impulse response.
4. Analyze, modify, and/or export your filter using any of ScopeFIR's other features.

Once a filter has been designed, you can check its Frequency Response. If the Automatic option is enabled, ScopeFIR will show you the frequency response at zero (DC) and at the peak of each major sidelobe. (See Using the Frequency Response List for more information on the Frequency Response list.)

*IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol ASSP-29, No. 2, April 1981