
Generally, only equalize the response in the passband, but you can sample further than the passband to
fine tune the cascaded response of the filter chain.
The CIC IP core generates a MATLAB script <variation_name>_fir_comp_coeff.m in the project directory.
You can run this script in MATLAB to generate FIR coefficients that provide appropriate passband
equalization. The generated coefficients are saved in a text file, for use by the Altera FIR Compiler
MegaCore function.
The MATLAB script requires the following parameters for the compensation FIR filter:
• L: FIR filter length, which is same as the number of taps or the number of coefficients
• F
S:
FIR filter sample rate in Hz before decimation/interpolation
• F
C
: FIR filter cutoff frequency in Hz
• B: Coefficient bit width if coefficients are written in fixed-point numbers
Figure 3-6: CIC and Compensation Filter Responses
Related Information
AN455: Understanding CIC Compensation Filters
CIC IP Core Parameters
Table 3-2: CIC IP Core Parameters
Parameter Value Description
Filter Specification
Filter type Decimator,
Interpolator
Selects a decimator or interpolator.
UG-CIC
2014.12.15
CIC IP Core Parameters
3-7
CIC IP Core Functional Description
Altera Corporation
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