Altera CIC MegaCore Function - Manual (Page 23)

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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