MultiRate

MultiRate refers to a set of concepts and techniques in digital signal processing that deal with signals operating at multiple sampling rates. The core idea is to change the sampling rate of a signal in a controlled and efficient way, allowing processing to occur at rates best suited to the task while preserving signal integrity. The two fundamental operations are decimation, which reduces the sampling rate, and interpolation, which increases it. Together they enable fractional-rate conversion and enable filters and transforms to run more efficiently than if all processing were performed at a single high rate.

A key technique in multi-rate processing is polyphase decomposition, where a filter is broken into several sub-filters that can be applied at different rates. This allows efficient implementation of sample-rate conversion and related operations. Anti-aliasing filters are essential when decimating to prevent spectral folding, while reconstruction filters accompany interpolation to suppress image components created by upsampling.

Multi-rate systems find wide applications across fields such as communications, where channelization and timing recovery benefit from rate changes; audio processing, where upsampling and downsampling harmonize streams with different playback or recording rates; and digital instrumentation or data acquisition, where resampling aligns data from diverse sources. Designers must manage trade-offs among fidelity, latency, and computational load, often selecting target rates that balance bandwidth requirements with available hardware resources.

In summary, multi-rate processing provides a flexible framework for handling signals across varying sampling rates, enabling efficient, accurate, and scalable digital signal processing in many applications.