Filterbands

Filterbands are the frequency ranges that are isolated by filters within a filter bank. In signal processing, a filter bank comprises multiple filters arranged so each filter passes a specific portion of the spectrum, producing a set of band-limited signals called subbands. Each subband corresponds to a filterband, defined by its center frequency and bandwidth. Filterbands can be uniform (equal bandwidth) or nonuniform to match perceptual or system requirements. In analysis filter banks, an input signal is decomposed into subbands, which can be processed independently and later recombined by a synthesis filter bank.

Key design considerations include the choice of passbands to minimize aliasing and overlap, the filter order and transition bandwidth, and the degree of overlap or guard bands between adjacent filterbands. Digital implementations often use polyphase or FFT-based filter banks for computational efficiency, while analog or mixed-signal designs may employ cascaded or ladder filter structures. Aliasing can occur if subbands are not properly spaced or if downsampling is used without adequate filtering.

Applications of filterbands appear in audio processing (such as crossover networks and equalizers), telecommunications (channelizers and multi-carrier systems), and spectrum analysis tools. While terminology often relies on the more general terms band or passband for a single filter, filterbands is a convenient way to describe the individual subbands produced or analyzed by a filter bank.