Processing Architecture
Digital signal processing structures use hardware-efficient stages to perform decimation or interpolation. A cascaded integrator comb filter achieves these rate changes without requiring multipliers. This hardware efficiency allows implementation in field programmable gate arrays where silicon resources are limited.
Sampling Transformation
Rate reduction occurs through a sequence of lossless integrators followed by a downsampler and a series of comb stages. The cascaded integrator comb filter removes high frequency images or prevents aliasing during these transitions. It operates at high sample rates because the front-end integrators do not involve complex arithmetic.
Register Implementation
Bit growth represents the primary design constraint in the integration stages to avoid overflow errors. Designers calculate the required word size based on the number of stages and the differential delay used in the comb section. Because the cascaded integrator comb filter lacks multipliers, the internal word length must accommodate the full DC gain of the filter.
Each integrator stage adds a pole at zero frequency, while the comb stages place zeros at multiples of the sampling rate. This specific arrangement creates a low pass response with a characteristic sinc shape.
Gain Calculation
Final output magnitude depends on the decimation factor raised to the power of the number of filter stages. Higher decimation ratios increase the processing gain. The cascaded integrator comb filter requires a compensating filter later in the signal chain to flatten the passband droop.
