Multirate Filters: An Overview

Multirate filtering techniques are widely used in both sampling rate conversion systems and in constructing filters with equal input and output rates in the case where the use of a conventional method becomes extremely costly. The purpose of this paper is twofold. First, this paper gives a short review on designing proper digital filters that are useful in providing the desired sampling-rate conversion between the output and input signals. Second, this paper shortly reviews on how to apply multirate technolgies as well as complementary filters for constructing digital filters in cases where the implementation of a conventional filter becomes, due to a too huge arithmetic complexity and the effects of finite word length effect, so large that this filter is not possible to construct in practice. In the second case, when using both multirate filtering and complementary filters enable one to share the overall filtering task between several simplified low-order sub-filters that operate at the lowest possible sampling rates and have significantly relaxed design constraints. Due to these facts, the resulting filter has significant reductions in the overall complexity as well in finite word-length effects