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Use multirate filters in digital signal processing systems when different sampling frequencies exist in different parts of a system, or when you want to reduce computational complexity in systems by using a uniform sampling frequency. You can change the sampling frequency of a filter by using decimation, interpolation, or rational resampling. This book describes the three filtering modes and the zero-phase filtering mode, which enables you to eliminate the delay between the input and output signals.

Use finite impulse response (FIR) structures to implement multirate filters. Compared to infinite impulse response (IIR) structures, FIR structures provide unconditional stability, phase linearity, and better finite-precision performance. Furthermore, FIR structures contain only feedforward signal paths that enable you to simplify the implementation of decimation and interpolation filters. In principle, you can use both lowpass and highpass FIR filters to implement multirate filters. However, the LabVIEW Digital Filter Design Toolkit provides lowpass multirate FIR filters only.

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