CIC Decimation

CIC filter is an optimized class of linear—phase FIR filters consisting of cascaded comb filters and integrators.

Conceptually, the decimation CIC filter is a CIC filter , which is a reconstructive low-pass filter and performs filtering without changing the sampling rate, followed by an element of lowering the sampling rate. Block CIC Decimation reduces the sampling rate of the input signal by an integer factor using a Cascaded integrated comb filter (CIC).

In a more efficient implementation, a CIC filter that works without changing the sampling frequency, it is decomposed into factors in this way:

where

The algorithm that provides full multi-rate filtering takes into account two remarkable identities for interpolation, which allow you to move the operation of changing the sampling frequency. for the cascade of comb filters without distorting the result of the operation.

The transfer function of the resulting filter is given by the following equation:

For a flowchart showing multi-speed implementation, see [algorithms].

The decimation CIC filter is implemented as a cascade of integrators, followed by an element of lowering the sampling rate of the signal in once, and then a cascade of comb filters.

The diagram shows a cascade of integrators with two sections and a cascade of comb filters, also consisting of two sections. The single delay in the CIC filter integrators can be located in both the forward and feedback circuits. These two configurations produce identical filter frequency characteristics. However, the actual numerical sequences in the output for these two configuration options will be different due to the effect of the delay. In this algorithm, a single delay is placed in the path of the direct line of the integrator, since this configuration is preferable for the HDL implementation.