Polyphase Implementation of FIR Decimation Block

This example shows the underlying polyphase implementation of the FIR Decimation block using downsampling and FIR filtering as building blocks. The model compares the output of the FIR Decimation block with the output of a polyphase decimation structure. The Time Scope block compares the two outputs.

Open the ex_polyphasedec.slx model.

The model has two branches. The first branch contains an FIR Decimation block. The second branch contains a polyphase decimation structure. For more details on the structure, see the Algorithms section in the FIR Decimation block page.

Run the model and view the results on the scope. The first signal on the scope is the original sinusoidal signal. The second and third signals on the scope are the outputs of the FIR Decimation block and the polyphase structure, respectively. The last signal on the scope shows that the error between the two decimated outputs is very small, almost zero. This negligible error confirms the underlying polyphase implementation of the FIR Decimation block.